we hear the words
natural and synthetic

all the time when talking about food,
medicine, clothes

and other things. but what do they mean?
if you took a poll

most people would tell you that natural
has to do with their juice cleanse

organic groceries, yoga and other healthy activities

but for synthetic they'll warn you of toxins

scary chemicals and mean confusing
chemistry teachers

with all these charged emotions it's not
surprising that a lot of people equate

these words with good and bad. but this discounts

everything chemistry has to offer
society, so we need to change this view

natural simply means made by nature, the
same benevolent force that brings us

deadly viruses and toxic blowfish

which looks strangely similar. synthetic means

made by humans who save lives with
antibiotics

and synthetic microbes that eat up the
oil from a tanker spill. now that we've

decoupled these words from good and bad

let's look at something both nature and humans

make. a vitamin is something we must
consume in small amounts

in order for our cells to keep normal
function and metabolism

most plants and animals make these on
their own but somewhere along biological

evolution

a few mammals lost the ability so we
have to eat them

take vitamin C. for thousands of years
we've gotten this from fruit

but with modern science we can identify
the structure of this and other

compounds

and make them ourselves. the question is

are they the same? to answer that

let's look at how a vitamin works. a
vitamin has just the right shape to fit

into an

active site of an enzyme and make
interactions that turn on the enzyme

like a lock and key. and just as it
doesn't matter who makes your key

as long as it's the right shape for the
lock, same goes for the vitamin

that's why any molecule that these
specific atoms

arranged in this way is vitamin C

nature makes this just fine, always has
but when nature does chemistry

it is limited to the normal pH and
temperature inside a living organism

so it has to use big bulky molecules

to do blind chemistry. when we do
chemistry

we can use any exotic compounds and
conditions we want to build

any molecule we want, and even though the pathways

are different the end product is the
exact same

molecule. so the bioactivity of a
molecule can not depend on how it came

to be

an enzyme simply can't tell the
difference. furthermore

it is often cheaper and easier to
synthesize these in mass quantities

than to have to extract and purify from
natural sources

so if we want to keep the growing global population

healthy and well-fed, we have to get over
the idea

that science looks like this, because
science

looks like this

Will Synthetic Vitamins Make Me Explode?

This was my final submission for the American Chemical Society's ChemChamps contest in 2015.

The words natural and synthetic are thrown around a lot these days, when talking about foods, medicine, and other things. But what do they really mean, and how are they different? Is one necessarily better than the other? Can the bioactivity of a molecule depend on its pathway? Let's answer these questions and more.

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMaths

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


It’s Professor Dave; let’s introduce the
distributive property.

As we learn math, we will see that there are
certain properties of numbers that are very

important.

We already learned about the commutative property
and the associative property, and we saw how

addition and multiplication abide by these
properties, while subtraction and division

do not.

Now let’s learn another property, the distributive
property.

To see how this works, let’s look at some
more apples.

Say we have five piles of seven apples.

Five piles times seven apples per pile gives
us thirty-five apples.

What if we split each pile up into a group
of three and a group of four?

There are a few ways we could represent this.

Let’s take the seven and split it up into
three plus four, in parentheses.

This is clearly the same value we once had,
because three plus four is seven, which makes

sense because rearranging the apples shouldn’t
change the number of them that are present.

But we could also say that we have five piles
of three and five piles of four.

That means five times three plus five times
four.

Visually, we are just describing what we see,
but mathematically, we have just derived the

distributive property.

When we have a number that is multiplied by
a sum or difference, we can distribute that

number across each value within the sum or
difference.

In this case, that means five times three
plus five times four.

That gives us fifteen plus twenty, which is
indeed still thirty-five.

So whether we add the numbers in the parentheses
first and then multiply by the other number,

or distribute the number across the sum, we
will get the same result, and that is the

essence of the distributive property, which
will be very important once we get to algebra.

We can even use this property in reverse.

Let’s say we have five times seventeen.

If we don’t want to write down a calculation,
we can easily do this in our heads if we split

seventeen up into ten plus five plus two.

Now, we can distribute the five across the
sum, and rewrite this as five times ten plus

five times five plus five times two.

These sums can be done easily in your head,
and we get fifty plus twenty-five plus ten,

and that’s eighty-five.

This sort of mental trickery is very useful
for multiplying large numbers, so let’s

move on to that topic next.

The Distributive Property for Arithmetic

We know about the commutative property and the associative property, but there are more to learn! This next one, the distributive property, is very important in algebra, so let's introduce it now so that when we get there we already have this covered.

Watch the whole Mathematics playlist: http://bit.ly/ProfDaveMath

Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


[Music]

the Pythagorean theorem is one of the

most well-known theorems in the history

of mankind it states that for any right

triangle a s + B2 is equal to c^2 most

people have seen this theorem but not

that many actually know the reason why

it's true today we're showing just that

to do this we take four copies of any

right triangle as shown here and then we

flip them to create the following image

then we want to arrange them in a way

like so to form a

square notice that the angles shown here

are complimentary so that the

intersection of the red lines actually

form 90° angles as shown

below now we have a red square basically

inscribed within a larger blue and green

square let's go further by asking what's

the area of the blue and green green

square the area of the blue and green

square can be given by its side lengths

so the side lengths are a plus b so the

area is a + b^ 2 which is equal to a 2 +

2 a + b

2 but alternatively we could have also

found the area from our figure by

noticing that the area is just four

copies of the area of each right

triangle plus the area of the Red Square

Square so now we have two alternative

definitions for the area of the large

blue and green square and we write it

below as shown

here now it just remains for us to

algebraically simplify this in the

following fashion and then to notice

that if we just subtract

2ab from both sides and do a little bit

of algebra we have exactly that a 2 + B2

is equal to C squ and this holds for any

generic right triangle I hope that's

shown some of the beauty behind the

mathematical proof of Pythagoras's

Theorem and actually showing you some of

the intuition and reasoning behind this

beautiful and very well-known

mathematical theorem thank you for

watching

[Music]

Proving the Pythagorean Theorem

Visualizing the Pythagorean theorem using Manim. Hope you enjoy, feedback is appreciated!

Music Credits:
Royalty Free Music: Bensound.com/royalty-free-music
License code: HEQ5SRCKWR9JYMGK

Chapters:

0:00 Introduction
0:20 Proving the Pythagorean Theorem
1:55 Ending


[Music]

Professor Dave and CH here a very

important thing to be able to do in

organic chemistry is to be able to

assign the formal charge of any atom in

a particular molecule atoms can be of

neutral charge or they can have a

positive or negative charge and

identifying atoms that have these

charges will help us predict what

molecule will do so let's make sure we

know how to do this the main thing to

understand is that an atom will be of

neutral charge when it is contributing a

number of electrons to a leis structure

that is equal to its veence for example

carbon has four veence electrons so when

it makes four bonds it contributes one

electron to each and is thus neutral

nitrogen has five veence electrons so

when it makes three bonds and has one

lone pair it is neutral If instead it

makes four bonds it contributes only

four electrons which is one less than

its veence so it has a formal positive

charge oxygen has six veence electrons

so when it makes two bonds and has two

lone pairs it is neutral but if it makes

only one Bond and has three loone pairs

it contributes seven electrons which is

one more than its veence so it will have

a formal negative charge this is the

easiest way to tell the formal charge of

any atom within a molecule here are the

most common situations we will be seeing

over and over again in organic chemistry

starting with carbon species here is a

carbon radical with three bonds and one

unpaired electron a carbo cation with

three bonds and an empty fourth

coordination site and a carban ion with

three bonds and one loone pair these are

neutral positively charged and

negatively charged respectively carbon

has four veence electrons but the

electrons being contributed to these

structures are four 3 and five

respectively so a carbon radical is

neutral just like a carbon that is

participating in four bonds a

carbocation has a formal positive charge

and a carban ion has a formal negative

charge then for nitrogen we have three

bonds and one loone pair four bonds and

no loone pairs or two bonds and two

loone pairs nitrogen has five veence

electrons and here we see contributions

of five 4 and six that means we have

neutral nitrogen

positively charged nitrogen and

negatively charged nitrogen moving on to

oxygen again we have two bonds and two

loone pairs three bonds and one loone

pair and then one Bond and three loone

pairs oxygen has six veence electrons

but these contribute six 5 and seven

respectively so we have neutral oxygen

positively charged oxygen and negatively

charged oxygen or an oxyanion which we

will see frequently then sulfur will

behave Just Like Oxygen since it also

has six veence electrons so by replacing

these oxygen atoms with sulfur atoms all

the same charges will apply and then

phosphorus is an analog of nitrogen and

we will sometimes see a phosphorus

cation when it is making four bonds to

other

atoms it is very important that this

ability of assigning formal charge to

any atom in a molecule becomes intuitive

because we need to know where the

charges are on a molecule to understand

how it reacts with other molecules

Professor Dave for che see you next

time

What Are Formal Charges? Ft. Professor Dave

In organic chemistry, it's important to be able to assign the formal charge of any atom in a particular molecule, in order to determine how these atoms may behave. Atoms can have a positive, negative, or neutral charge—let's learn how exactly to determine an atom's formal charge, and how the concepts of bonds and valences fit in with this determination.

Get more homework help from Chegg at https://che.gg/3HbtG8Y
Watch the whole Organic Chemistry playlist: https://www.youtube.com/playlist?list=PLllCkartRRdMPnATf1X8qVdo5RzM8gA_M

About Chegg:
Chegg is a leading education technology company that provides students with affordable and accessible study resources. Chegg's mission is to help students save time, save money and get smarter.

Subscribe: https://www.youtube.com/@chegg
TikTok: https://www.tiktok.com/@chegg
Instagram: https://www.instagram.com/chegg/
Twitter: https://twitter.com/chegg

00:00 Intro
00:33 Valence electrons
01:28 Carbon species
02:13 Nitrogen species
02:35 Oxygen/sulfur species


hey professor dave let's check out the

night sky

[Music]

it's taken almost 10 billion years but

we finally made it we started with a big

bang

we watched adam's form

we saw these collect forms stars and

galaxies we saw those stars explode to

disperse the materials that would become

all the planets and we watched our own

solar system form including the planet

earth thus begins a new chapter of the

story

upon this earth biomolecules arose

polymerized and became contained in cell

membranes life was born which slowly

evolved and eventually brought about

human beings like you and me this

fascinating chapter of the story is told

by the field of general chemistry

organic chemistry biochemistry and

biology check out my tutorials on those

subjects if you want to know more about

that whole show since it's more than a

little involved as one might

imagine i just thought it'd be fun to

have a little persona professor dave

it's just a little name um you know i

don't know

anything but i you know did uh work in

um you know i took courses without

components uh in as an undergrad and

then i did most of the masters in

synthetic but i didn't really last long

i dropped out of my semester

again for music opportunities and i

eventually got this teaching job uh for

organic chemistry at this little trade

university it was pretty great because

the bachelor's degree i was supposed to

teach the laboratory portion but on the

first day the lecture instructor had

this freakout we just took

[Music]

you're not enjoying chemistry but

through a bunch of bureaucracy quite

frankly i lost that job withdrawal yet

again from from the master program a lot

of you asked very infectiously are you a

real professor i sit literally in this

room uh like 60 to 70 hours a week and

uh i chose the name really without much

thought uh it was kind of telling you to

be honest right um i just thought it'd

be fun to have a little personal

professor it's just a little name

through a bunch of bureaucracy and i

lost that job i chose the name it was

kind of pungent to be honest so and even

at that time i had no interest in being

a chemist i do not enjoy the industries

i really really hate it

[Music]

you

Hey! it’s Professor Dave 😁

we saw and watched it all... 😂

it’s not so much about WHAT he says as it’s BS anyway... my point is: this guy who isn‘t even a real Professor has 2 Million followers!!! (how many bots... idk)

so by that you can see how brainwashed and indoctrinated people are... I‘m sure he get’s paid from the US tax money 🤷🏻♀

and this stupid intro... c’mon!!! I wouldn't even put my children through that... SMH

#indoctrination #brainwashedsociety
#useyourbrain
#washyourhands 😆😂🙄
#stayreal 🙏🔥


here's the homework problem as you know

last week

we caught a mistake with sal khan from

khan academy this week we found another

mistake from

another famous physics professor

his channel named professor dave

explains let's take a look he knows a

lot about the science stuff

if you compress the spring and put a

little 0.01 kilogram army guy on top

how high will it be launched when you

release the spring

and this is the answer as it happens we

could use

this same equation again and we could

plug in

our initial velocity as well as a final

velocity

of zero since velocity will be zero

at the moment that the object reaches

the peak

of the trajectory and we get 1.35 meters

this is wrong so i want you to

get the right answer

Lunching Things with Spring : Fix the mistake Professor Dave made

Learn Math & Science @ https://brilliant.org/BariScienceLab


okay number four asks which of the

following is the strongest base that

means that we're looking at the ability

of these compounds to accept a proton in

all of these cases we're looking at some

lone pairs on oxygen and nitrogen so

this oxygen has two lone pairs this

oxygen has two lone pairs this nitrogen

has one lone pair and this nitrogen has

one lone pair in each case an acid base

reaction is going to occur whereby

either oxygen or nitrogen is accepting a

proton with a lone pair and so which is

able to do it best now what we have to

understand is that these lone pairs are

not all equally available for acid base

reactions some of them are tied up in

resonance so for example over here on

this phol we've got a lone pair that can

get pushed down here and then all of

this Pi electron density can be

delocalized we have a lot of different

res

Which is the Strongest Base?

This is an abbreviated version of this question for YouTube Shorts. Check out the full version in the linked video.


معكم البروفيسور ديف ,لنتحدث عن كيمياء الأكسدة والاختزال

تفاعل الأكسدة والاختزال أو تفاعل الأكسدة والاختزال

هو الذي يحدث فيه نقل إلكترون

خذ على سبيل المثال هذا التفاعل

شاهد ما يحدث إذا كتبنا المعادلة الأيونية الصافية

تشطب الكبريتات ونرى أن الكيمياء الوحيدة التي حدثت هي أن إلكترونين ينتقلان من الحديد إلى النحاس

فقد الحديد الإلكترونات ،اذاً فقد تأكسد

اكتسب النحاس إلكترونات لذلك تم تخفيضه

قد يبدو الأمر مربكًا لربط الاختزال بكسب الإلكترونات

لذا بدلاً من ذلك ، قم بربط الخفض بخفض الشحنة

النحاس 2+ تم تخفيض شحنته إلى الصفر عندما اكتسب إلكترونين

المزيد من الإلكترونات يعني شحنة أكثر سلبية أو أقل شحنة

المادة المؤكسدة هي عامل الاختزال لأنه الشيء الذي تسبب في انخفاض المادة الأخرى

وبالمثل فإن المادة التي يتم تخفيضها هي مادة الأكسدة، لأنها تسببت في أكسدة المادة الأخرى.

سنستخدم أعداد الأكسدة لتتبع تدفق الإلكترونات.

وهذه القيم تشبه قيم الشحن الافتراضية لكل ذرة في جزيء

لكنها ليست شحنات كهربائية فعلية

فيما يلي بعض القواعد لتعيين أرقام الأكسدة

بالنسبة لعنصر ، يكون رقم الأكسدة دائمًا صفر

إذا كان أيون أحادي الذرة ، فإن رقم الأكسدة هو نفس الشحنة الموجودة على الأيون.

يكون الأكسجين دائمًا -2 باستثناء البيروكسيدات, اذا بامكاننا الافتراض انه 2- احيانا

لأعداد أكسدة الجزيء المحايدة يجب اضافته حتى الصفر

لذلك إذا كان الأكسجين الموجود في ثاني أكسيد الكربون لكل منهما -2 ، فيجب أن يكون الكربون +4

بالنسبة لأيونات متعددة الذرات

يجب أن تضيف أرقام الأكسدة إلى الشحنة الموجودة على الأيونات والهيدروجين تقريبًا +1 تقريبًا.

لذا باستخدام هذه الأرقام للأكسجين والهيدروجين

يمكننا عادةً تعيين جميع الأرقام الأخرى وفقًا لذلك.

دعنا نلقي نظرة على هذا التفاعل، على اليسار لدينا عناصر اذاً رقم الاكسدة لها هو صفر

على اليمين نعلم أن الأكسجين سيكون -2 وهناك ثلاثة منهم

لذلك نحتاج إلى الحديد ليكون + 3 لكل شيء يضاف إلى الصفر

هذا يعني أن الحديد تأكسد بسبب زيادة عدد الأكسدة.

كان الأكسجين هو العامل المؤكسد

تم تقليل الأكسجين أيضًا نظرًا لانخفاض عدد الأكسدة الخاص به

ذلك يجعل الحديد هو عامل الاختزا.

لنتحقق من مدى الاستيعاب

شكرا لمشاهدتكم اشتركوا في قناتي للمزيد من الدروس

وكما هو الحال دائمًا ، لا تتردد في مراسلتي عبر البريد الإلكتروني

Oxidation-Reduction Reactions

Which thing gets oxidized, the oxidizing agent? No wait, that's what gets reduced, or is it the reducing agent? Ahh! Stupid binary concepts! OK, settle down. Watch this clip and learn everything you need to know about electron transfer.

Watch the whole General Chemistry playlist: http://bit.ly/ProfDaveGenChem

Study for the AP Chemistry exam with me: https://bit.ly/ProfDaveAPChem

Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMaths

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


Introduction to the Italian Language

It's time to learn Italian! Whether you're studying Italian in school or you just need a few phrases to visit Italy, this is the playlist for you! Vocabulary sorted by category, easy-to-understand explanations of all the tricky grammar, and lots of tips regarding culture and etiquette so that you don't make a fool of yourself in Firenze!

Just in case you're skeptical of this content, I must inform you that this series is the result of a collaboration between myself and my mother, Patrizia Farina, a native Italian who has taught the language to undergraduates for the past 30 years. So this is the real deal! We will follow her rigorous curriculum through multiple beginner and intermediate Italian courses, which means you won't find better Italian tutorials anywhere on the internet! So what are you waiting for, dig in!

Watch the whole Italian playlist: http://bit.ly/ProfDaveItalian

American History Tutorials: http://bit.ly/ProfDaveAmericanHistory
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


so let's practice calculating
equilibrium concentrations

consider the following equilibrium with
N2 + 3H2 in equilibrium with 2NH3

now at equilibrium the nitrogen
concentration is 4 point 2 6 molar the

hydrogen concentration is 2 point zero 9
molar and the equilibrium constant for

this system is zero point zero six zero
zero what is the equilibrium

concentration of NH3? so if this seems
confusing check out my tutorial on

equilibria and then give this a try.

so this is a very straightforward situation

here is our equilibrium now the first
thing we want to do is generate our

equilibrium constant expression now
recall that will involve placing the

concentrations of the products over the
concentrations of the reactants and then

the concentrations are going to be
raised to the power of the relevant

stoichiometric coefficient so whatever
the coefficient is on a substance the

concentration of that substance will be
raised to that power so in this case we

have our equilibrium constant being
equal to the concentration of ammonia

squared because ammonia has a
coefficient of 2 over the concentration

of nitrogen times the concentration of
hydrogen raised to the 3rd power because

hydrogen has a coefficient of 3 so that
is our expression and now we just plug

in what we know and as it turns out we
know everything except one thing so we

have that constant it is zero point zero
six zero zero we have our nitrogen

concentration it's four point two six
and we have our hydrogen concentration

it's two point zero nine
and that will be raised to the third

power so here all we have to do is a
little bit of arithmetic and we get the

ammonia concentration squared as being
equal to two point three three and then

we take the square root and our answer
will be one point five three molar.

Practice Problem: Calculating Equilibrium Concentrations

We know how to write equilibrium constant expressions for any equilibrium, and we know that they relate the equilibrium constant to the equilibrium concentrations for all of the substances in the system. Let's see if we can calculate a missing equilibrium concentration when other data is given!

Try all of the general chemistry practice problems: http://bit.ly/ProfDaveGCPP

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


okay let's try a question
relating to spontaneity consider the

conversion of limestone to lime so we
have calcium carbonate caco3 yielding

calcium oxide CA o and co2 gas the
values of Delta H and Delta S are 179

point 1 kilojoules per mole and 160
point 2 joules per Kelvin respectively

at 298 K and 1 bar assuming that these
values do not change with temperature

what is the temperature above which
conversion of limestone to lime will be

spontaneous so we need to know some
things about Gibbs free energy enthalpy

entropy we need to know how those values
correlate we need to know something

about the conditions within which a
reaction will be spontaneous so go ahead

and check out my tutorial on Gibbs free
energy if you need some review and when

you're ready give it a try

so the first
thing we have to remember is that

reactions are spontaneous when Delta G
is less than zero so we need Delta G to

be negative in order for a reaction to
be spontaneous so if we have Delta G

equals Delta H minus T Delta s and we
need Delta G to be less than zero then

we also need Delta H minus T Delta s to
be less than zero because those are

equivalent now because we're trying to
figure out the temperature above which

conversion of limestone to lime will be
spontaneous that means we're going to be

solving for a temperature so let's
rearrange this inequality to solve for

temperature all we do is add T Delta s
to both sides and then divide by Delta s

and we get T is greater than Delta H
over Delta S so we can just go ahead and

plug in the
use that we know now we have 179.1

kilojoules per mole for Delta H but our
entropy value has joules so these are

gonna need to agree let's just go ahead
and multiply this one by a thousand that

way we'll have it in joules so one
hundred and seventy-nine thousand one

hundred joules per mole and then we can
divide that by a hundred and sixty point

two joules per Kelvin that way the
joules will cancel and we end up with

1118 Kelvin so that means that despite
the enthalpic unfavorability we see that

this is endothermic right one hundred
seventy nine point one kilojoules per

mole this is an endothermic reaction
which we typically expect to not be

spontaneous however it is entropically
favorable we're producing more

substances we're producing a gas
therefore if we raise the temperature

high enough that T Delta s term will
outweigh the Delta H term and it happens

to be this value 1118 Kelvin above that
temperature this will be a spontaneous process.

IIT/JEE Chemistry Practice #30: Spontaneity

Practice REAL problems from actual past IIT/JEE exams with Professor Dave!

Try all of the IIT/JEE chemistry practice problems: http://bit.ly/ProfDaveIITJEEChem

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


okay number eight asks which is the

lowest energy confirmation for

cyclohexene so this one's pretty

straightforward option A is chair let's

just draw the chair really quick and so

what we need to understand about the

chair is it does a couple of things

first it allows for all of the carbons

to obey the perfect tetrahedral geometry

that they enjoy for example we've got

two hydrogens right here we can

essentially imagine this as being a

wedge Bond and this as being a dash Bond

down to those other carbons but however

you want to visualize it it has that

perfect tetrahedral geometry with 109.5

degree Bond angles and then the other

thing it does is that all of the Newman

projections for all of these bonds would

put the different alkal groups as anti

to one another so for example this

carbon carbon bond is anti to this

carbon carbon Bond and you can do that

for all the carboncarbon bonds so number

one there are no eclipsing interactions

the alal are not eclipsing

Conformations of Cyclohexane


فكرة أن قارات كوكبنا تنجرف حول الأرض بشكل دوري، تتصل ببعضها

وتتباعد عن بعضها البعض، هي فكرة عمرها ٢٠٠ سنة. لكن أغلب علماء الأرض لم يصدقوها

إلا في الستينات عند تزايد ظهور الأدلة التي وضحت أن قشرة الأرض

انقسمت إلى أجزاء، وأن هذه الأجزاء المسماة بالصفائح التكتونية دائمة الحركة.  وفي هذه

الأيام نقوم دائمًا بمراقبة هذه الحركة - بدقة المليميترات - من خلال الفضاء.

التفسير الشائع والمبسط لحركة الصفائح التكتونية هو أنها

محمولة فوق تيارات الغشاء العلوي للأرض، وهو الطبقة الصخرية المتحركة ببطء والواقعة مباشرة تحت

قشرة الأرض. تقرب التيارات المتلاقية الصفائح من بعضها البعض، بينما التيارات المتباعدة

تبعدها عن بعضها البعض.

هذا صحيح في الغالب، فالصخور الغشائية الحارة ترتفع من لب الأرض وتتحرك تحت القشرة الأرضية

حتى تبرد وتثقل وتعود للأسفل مرة أخرى، ولكن هذه الصفائح

لا تتحرك فوق التيارات بشكل ساكن مثل مجموعة من الحقائب فوق الحزام الناقل للأمتعة.

لأن بعض الصفائح تتحرك بشكل أسرع من التيارات الموجودة أسفلها.

وعلى سبيل المثال، صفيحة نازكا - وهي قطعة من القشرة المحيطية تقع في الساحل الغربي لأمريكا الجنوبية -

تبحر شرقا حوالي ١٠ سنتيميترات في السنة، بينما يتحرك الغشاء

أسفلها ٥ سنتيميترات فقط. لا تستطيع الصفائح التكتونية أو الأمتعة الحركة بشكل أسرع

من الحزام أسفلها، إلا بمساعدة قوة خارجية تدفعها أو تسحبها.

وكما يتضح أن بعض صفائح الأرض تقوم بسحب نفسها. عندما تصطدم

صفيحة محيطية بصفيحة محيطية أخرى أو صفيحة تحمل قشرة سميكة من القارة،

فإن الصحيفة الأقل سمكًا تنحني وتنزلق تحت الأخرى. وحينما ينزل قاع البحر

إلى غشاء الأرض فإنه يسحب معه الصفيحة التي في الخلف، مثلما تتدلى سلسلة أبعد

وأبعد من فوق طاولة حتى تسقط في النهاية. فكلما كان الجزء الغائر من الصفيحة أكبر

كلما أصبح الجزء المتبقي منها فوق الغشاء أقوى وأسرع في الحركة.

بإمكانك رؤية أين يحدث هذا عن طريق قوقل أيرث، فالخنادق المحيطية العميقة والضيقة

التي يمكن رؤيتها من سواحل بعض القارات وسلاسل الجزر تحدد الطويات

المتكونة عند إتجاه قشرة المحيط للأسفل، والمتسببة بميل القارة المجاورة لها خلال عملية الإنحناء.

وعلاوة على ذلك، تساعد هذه الكتل من قاع البحر في انتقال الحرارة إلى

الغشاء الذي يقع أسفلها. وتمنع ألواح قشرة المحيط الغائرة الصخور المندفعة من الحركة نحو الجوانب،

مجبرة هذه الصخور للإتجاه نحو الأسفل مما يجعل الألواح بأن تصبح أثقل

وبالنهاية تنكسر وتغوص نحو لب الأرض مكونة قوة سحب

تسحب المواد الغشائية خلفها. نوعًا ما، نستطيع القول بأن قشرة قاع المحيط هي جزء

من حزام النقل وليست شيء فوقه، بينما القارات

هي الأمتعة.

ترجمة فريق @autrjim

Plate Tectonics Explained

How do plate tectonics REALLY work?

Please support us on Patreon at: http://www.patreon.com/minuteearth

And subscribe! - http://www.youtube.com/user/minuteearth?sub_confirmation=1

Thanks to our Patreon patrons:
   - @AntoineCoeur
   - salar tel
   - @TodayIFoundOut1
   - @82abhilash

________________________
Created by Henry Reich
Production and Writing Team: Alex Reich, Peter Reich, Emily Elert, Ever Salazar, Kate Yoshida, and Henry Reich
Music by Nathaniel Schroeder: http://www.soundcloud.com/drschroeder

________________________
Free iTunes podcasts of MinuteEarth! - https://goo.gl/sfwS6n
Facebook - http://facebook.com/minuteearth
Twitter - http://twitter.com/MinuteEarth

MinuteEarth provides an energetic and entertaining view of trends in earth's environment -- in just a few minutes!

________________________
References

Anderson, D. L. (2001). Top-down tectonics?. Science, 293(5537), 2016-2018. http://www.sciencemag.org/content/293/5537/2016.short

Conrad, C. P., & Lithgow-Bertelloni, C. (2002). How mantle slabs drive plate tectonics. Science, 298(5591), 207-209. ftp://128.171.151.230/engels/Stanley/Textbook_update/Science_298/Conrad-02.pdf

Conrad, C.P., 2014. Personal Communication

Dietz, R. S. (1961). Continent and ocean basin evolution by spreading of the sea floor. Nature, 190(4779), 854-857. http://eps.mcgill.ca/~courses/c350/lecturestuff/jan28/Dietz_1961.pdf

Forsyth, D., & Uyeda, S. (1975). On the relative importance of the driving forces of plate motion. Geophysical Journal International, 43(1), 163-200. http://gji.oxfordjournals.org/content/43/1/163.short

Hecht, J. 2014, Aug 29. Earth's tectonic plates have doubled their speed. New Scientist. http://www.newscientist.com/article/mg22329843.000-earths-tectonic-plates-have-doubled-their-speed.html#.VBDAJ7ywJ_Q

Smil, V. 2007. Energy in Nature and Society: General Energetics of Complex Systems. MIT Press. http://mitpress.mit.edu/books/energy-nature-and-society

Driving forces of plate tectonics (website):
http://www.columbia.edu/~vjd1/driving_forces_basic.htm


Professor Dave here, let's talk about the

third law of thermodynamics.

We've gone through three of the laws of

thermodynamics, which leaves just one to

go, and the third law of thermodynamics

deals with another strange concept: the

idea of a temperature of absolute zero.

We know that temperatures can get very

hot and very cold, but not everyone is

familiar with the idea of the coldest

possible temperature. However, with our

new understanding of heat and

temperature, it should make perfect sense.

We know that temperature is a measure of

available heat energy, which is just a

collection of kinetic energies of motion.

We know that as the temperature

decreases, the internal energy of a

system decreases, as does the kinetic

energy of each particle. As the

temperature becomes very cold, particles

slow to a complete stop, and there is no

more kinetic energy. No more kinetic

energy of motion means no more

temperature by any real definition of

the term, so we will call this absolute

zero. At absolute zero, every substance

would be a solid, even things like

hydrogen and helium, and one way of

summarizing the third law of

thermodynamics is by saying that the

entropy of any crystalline substance at

absolute zero will be equal to zero. This

is a necessary consequence of

Boltzmann's equation, S equals k times

the natural log of W. If there is no

kinetic energy, nothing is moving, so

there is only one possible microstate

that the particles can inhabit. With a

value for W equal to one, the natural log

of 1 is 0, so at absolute zero the

entropy of any substance must also be

zero. However, absolute zero can never

truly be reached, which is communicated

in a rephrasing of the third law which

states that it is impossible to lower

the temperature of any system to

absolute zero in a finite number of steps.

Satisfactory analysis of this law will

require the quantum mechanical

zero-point energy, and will thus have to

wait until the modern physics course.

This concludes our analysis of the laws

of thermodynamics, a near mythical

accomplishment in the history of science.

It also means we have covered some of

the harder stuff in physics, so now we

get to move on to fun things like waves

and magnets. But first, let's check comprehension.

Thanks for watching, guys. Subscribe to my channel for

more tutorials, support me on patreon so I can

keep making content, and as always feel

free to email me:

The Third Law of Thermodynamics: Absolute Zero

Brr, it's so cold today! Could it get any colder? Is there a coldest possible temperature? Yes, there is! That seems strange, but now we know that temperature is just a measure of kinetic energy, so zero kinetic energy must mean zero temperature! Let's learn more about this winter wonderland of physics as we wrap up our adventures with the laws of thermodynamics.

Watch the whole Classical Physics playlist: http://bit.ly/ProfDavePhysics1

Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMaths
General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


three what is the iup pack name for the

following compound we have another one

here we have a cyclohexane so the way

that we name cyclohexanes is a little

bit different from linear molecules what

we need to do is we need to find the

lowest set of locant possible so we have

three substituents and we need to number

the ring so as to give them the lowest

set of locant possible one could be any

of these carbons and then we go either

clockwise or counterclockwise but it

happens to be the case that this is the

lowest set of locant that we can get is

if we do 1 2 4 so if we started with the

ethyl we could get 134 if we started

with the bromo we could get 125 right

none of these are the lowest possible

the one that I've drawn right here

that's the lowest set of loans possible

we have to do it that way because these

alkal and hallogen substituents are all

of equal priority so we just go 1 2 3 4

5 6 like that

IUPAC Nomenclature of a Cycloalkane


Before we take a look at how osmosis and tonicity affect

a cell, let’s review what each of these terms means.

Osmosis represents the diffusion of water across a semi-permeable

membrane.

The term tonicity refers to the relative solute concentration

of two environments separated by a semipermeable membrane.

In other words, by comparing the tonicity of the solution,

you can determine the direction in which osmosis will occur.

To demonstrate how tonicity affects a cell,

let’s place some red blood cells into a beaker containing pure water.

In this case, the solute concentration is greater inside

the cells, than in the surrounding water.  In other words,

the contents of the cells are hypertonic in relation to the hypotonic

contents of the beaker.  Because of this, osmotic

pressure results in the diffusion of water across the membrane and into the

cells.  Over time, if enough water enters the cells,

the cell membranes may burst.  This is called lysis.

Now lets place the red blood cells in a beaker containing a solution

of salt, such as sodium chloride.  Since the contents of the beaker

beaker are hypertonic in relation to the interior of the cell,

the water within the cell will diffuse across the membrane and into the

contents of the beaker.  This causes crenation or shrinking of

the cells.

If the red blood cells are placed in a beaker whose contents

match the tonicity within the cells, then there is no net gain

or loss of water.  The environments within the beaker

and inside the cells are said to be isotonic, or the same.

An important thing to remember, is that osmotic pressure

always causes water to move from a hypotonic environment toward

a hypertonic environment.  In other words, water moves toward

areas of high salt or sugar concentrations.  This simple

process is used to drive the operation of our kidneys and explains

some of the physiological consequences of diseases such as diabetes.

Osmosis and Tonicity

This 2 minute animation describes the relationship beteween osmosis and tonicity.  Find more free tutorials, videos and readings for the science classroom at ricochetscience.com


البروفيسور ديف هنا, سأحدثكم عن تحليل العناصر

لنفترض أن لدينا هيدروكربون غير معروف

هذا الجزيء يتكون من الهيدروجين والكربون فقط

لنفترض أيضًا أننا نريد معرفة الصيغة التجريبية للهيدروكربون

أو أدنى نسبة كاملة من الكربون لذرات الهيدروجين

في الجزيء. هل هي 1 إلى 2 ، 1 إلى 3

3 إلى 5؟ منذ فترة، توصلنا إلى طريقة ذكية لحل شفرة هذه النسبة

عندما نحرق الهيدروكربونات ، نحرقها في وجود الأكسجين

نحصل على ثاني أكسيد الكربون والماء كمنتج

لذلك ينتهي كل الكربون في الهيدروكربون في جزيئات ثاني أكسيد الكربون

وكل الهيدروجين ينتهي في جزيئات الماء

لقد طورنا هذا الجهاز الأنيق حيث تكون عينة من الهيدروكربونات معروفة الحجم

يتم وضعها هنا على شعلة, الأنبوب مفتوح للسماح بدخول الأكسجين

ثم تنتقل المنتجات المتبخرة بهذه الطريقة عبر هذه المواد

مادة واحدة تمتص الماء وتمتص الأخرى

ثاني أكسيد الكربون, نزن هذه المواد قبل وبعد التجربة

والفرق سيكون كتلة الماء وثاني أكسيد الكربون

الممتصة على التوالي

لذا دعنا نقول أن لدينا عينة من البنزين ولكن ليس لدينا أي فكرة عن نسبة

الكربون للهيدروجين

نحرق عينة 0.342 جرام

ونجمع 1.156 جرامًا من ثاني أكسيد الكربون

هنا, لأن ثاني أكسيد الكربون يزن 44 وحدة كتلة ذرية

وتزن ذرة الكربون 12 ، كل جزيء من ثاني أكسيد الكربون

27.3٪ كربون بالكتلة

هذا يعني أنه يوجد في ثاني أكسيد الكربون 0.316 جرامًا

من الكربون, إذاً منلعينة الهيدروكربون الأصلية

بهذا القدر منها يجب أن يكون معظمها من الكربون والباقي

يجب أن يكون الهيدروجين

هذا يجعل الهيدروكربون 92.4٪ كربون

و 7.6٪ هيدروجين بالكتلة

نسميها نسبة تكوين البنزين, لنذهب خطوة أبعد ونجد

الصيغة التجريبية

إذا اعتبرنا أن لدينا 100 جرام من الهيدروكربون

92.4 جرامًا من الكربون و 7.6 جرامًا من الهيدروجين

باستخدام كتلها الذرية للتحول إلى المولات نحصل على 7.6 مولات تقريبًا لكل واحد

مما يشير إلى نسبة واحد إلى واحد. وبالتالي

الصيغة التجريبية للبنزين هي CH. هذا يعني أن هناك نفس العدد من

ذرات الكربون

مثل ذرات الهيدروجين في الجزيء

إذا أردنا إيجاد الصيغة الجزيئية التي تمثل العدد الفعلي

لذرات كل عنصر في الجزيء,  نحتاج إلى الكتلة الجزيئية

لنفترض أننا نعلم أن الكتلة الجزيئية للبنزين هي 78

وحدة واحدة من الصيغة التجريبية تزن 13

و 78 مقسومة على 13 هي ستة, وهذا يعني أننا بحاجة إلى ست وحدات

الصيغة التجريبية للحصول على الصيغة الجزيئية أو C6H6

دعونا نتحقق من مدى الاستيعاب

شكرا لمشاهدتكم اشتركوا في قناتي للمزيد من الدروس

وكالعادة لا تتردد في مراسلتي عبر البريد الإلكتروني

Elemental Analysis: Empirical and Molecular Formulas

There's a thing with carbon and hydrogen in it. But how many of each?! That's the kind of thing a chemist should know. So let's do some elemental analysis!

Watch the whole General Chemistry playlist: http://bit.ly/ProfDaveGenChem

Study for the AP Chemistry exam with me: https://bit.ly/ProfDaveAPChem

Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMaths

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


[Music]

button

[Music]

Professor Dave and Chegg here we've been

discussing galvanic cells from a more

practical standpoint but it will also be

useful to talk about the thermodynamics

behind them so that we can get a more

fundamental understanding of this

phenomenon so let's do that now we know

that a galvanic cell involves a

spontaneous redox reaction generating an

electric current that can be used for

some practical purpose this is because

the flow of electrons which is what an

electric current is can do work just

like water spontaneously flowing

Downstream in a river can do work and

push a water wheel which can then drive

some mechanical function so too can a

spontaneous flow of electrons do work

this electromotive force is defined in

terms of a potential difference between

two points in a circuit measured in

volts kind of like a gravitational

potential difference from a higher

elevation where a river starts and some

point of lower elevation Where the River

Flows to recall that a volt represents a

jewel of work per coulomb of charge

transferred so V equals J over C in the

context of an electrochemical cell we

consider work to be negative when

flowing out of the system such as when a

galvanic cell produces a current cell

potential is related to work and charge

by this equation so we can see that a

negative value for work results in a

positive cell potential which is also

characteristic of a galvanic cell as we

know from learning about the second law

of Thermodynamics some of the work

produced by galvanic cell will always be

lost to the environment rather than

going toward the cell potential the wire

that allows for current flow will

produce heat such that the maximum work

possible is not physically attained

again this is because the entropy of the

universe must increase for any

spontaneous process and this dispersal

of energy in the form of heat is what

produces this increase in the entropy of

the universe

despite the fact that we can never

harvest the maximum work possible from a

galvanic cell we can still make

approximations with the following

equation where work equals the opposite

of charge transferred which is the moles

of electrons transferred times Faraday's

constant times the actual potential

difference

this can also be expressed in terms of

the change in free energy and if we want

to know about the standard free energy

change we simply change the cell

potential to the standard cell potential

with the appropriate superscript this

means that the maximum cell potential is

directly related to the free energy

difference between reactants and

products in the cell for example given

this galvanic cell with copper and iron

and their Associated reduction

potentials what is the standard change

in free energy for the cell well first

we calculate the cell potential which

will be 0.78 volts that goes in the

equation along with Faraday's constant

and also two for moles of electrons

because two electrons are being

transferred for every copper ion doing

the math we get Negative 1.5 times 10 to

the 5 joules

and now we have a better understanding

of how cell potential relates to

electrical work and free energy

Professor Dave for check see you next

time

thank you

Cell Potential, Electrical Work, and Free Energy | Professor Dave & Chegg Explain

Professor Dave explains the basics of cell potential, electrical work and free energy. He defines galvanic cells, explains how to calculate cell potential, and covers the formulas of work and cell potential.

Get more homework help from Chegg at https://che.gg/3HbtG8Y
Watch the whole General Chemistry playlist: https://www.youtube.com/playlist?list=PLllCkartRRdPQdEE-oyt5Di31wIwJc5S6

About Chegg:
Chegg is a leading education technology company that provides students with affordable and accessible study resources. Chegg's mission is to help students save time, save money and get smarter.

Subscribe: https://www.youtube.com/@chegg
TikTok: https://www.tiktok.com/@chegg
Instagram: https://www.instagram.com/chegg/
Twitter: https://twitter.com/chegg

00:00 Intro
00:11 Galvanic cells
00:50 Cell potential
01:37 Second law of thermodynamics
02:08 Work and cell potential


[Music]

Professor D Dave and CH here we should

remember quite a bit about acids and

bases especially the Bron stead Lowry

model which is the model of acidity and

basicity we will most frequently use

describing acidbase reactions in the

context of proton transfer but there is

another model that we will sometimes be

using in organic chemistry and that is

the Lewis model let's review this model

as well since it will be relevant to a

number of important mechanisms we see

later rather than focusing on proton

transfer this model looks at electrons

alouis acid is a substance which accepts

a pair of electrons while a Lewis base

is one which donates a pair of electrons

in truth there isn't much difference

between a Lewis base and a bron stad

Lowry base as even when proton transfer

is involved it requires a lone pair from

some base which can coordinate to the

proton hence an electron pair donor but

the difference is quite significant when

looking at aets because the leis model

will often involve a base coordinating

to some atom rather than accepting a

proton for example let's look at Boron

Tri fluide BF3 this Boron atom has a

substantial partial positive charge

because of the polarity of these Boron

Florine bonds because of this electron

deficiency it is prone to attack by

electrons since positive charges and

negative charges attract which is

essentially the central theme of the

entire field of chemistry so a lwi base

like this fluoride ion can attack the

Boron atom to form a new Bond leaving us

with BF4 minus we will call this product

an acid base adduct so we won't get

conjugate species like with the Bron

stead Lowry model one of the reasons

this is relevant in organic chemistry is

that we will frequently see metal cat I

acting as Lewis acids take the Magnesium

2+ ion

this is electron deficient due to the

formal positive charge so electrons can

coordinate to it this means that we can

often find metal cations like this

coordinated to Regions with a formal

negative charge on certain kinds of

molecules especially

oxyanion like here with this phosphate

ion transition metals also frequently

form Lewis acids compounds like

zncl2 and sncl4 are all Lewis acids due

to having a central electron deficient

atom which is susceptible to attack from

a LS base again with bases things are

not much different conceptually from a

bron dead Lowry base the difference is

that a Lewis base doesn't specifically

have to coordinate to a proton it can

coordinate to something else and will

still qualify as a LS base many oxygen

and nitrogen containing compounds can

act as Lewis bases due to the lone pair

of electrons on these atoms as well as

sulfur with that we should have a basic

understanding of the Lewis model for

acidity and basicity as well as some

important examples of Lewis acids that

will come up as we study organic

chemistry professor Dave for che see you

next time

What Are Lewis Acids and Bases? Ft. Professor Dave

Now that we've covered the Brønsted-Lowry model of acidity and basicity, let's take a look at a different model: the Lewis model. With @ProfessorDaveExplains, we'll learn about how the Lewis model looks at electrons instead of proton transfer, and then we'll cover the concept of an acid-base adduct with the example of boron trifluoride. Finally we'll discuss how metal cations can act as Lewis acids.

Get more homework help from Chegg at https://che.gg/3HbtG8Y
Watch the whole Organic Chemistry playlist: https://www.youtube.com/playlist?list=PLllCkartRRdMPnATf1X8qVdo5RzM8gA_M

About Chegg:
Chegg is a leading education technology company that provides students with affordable and accessible study resources. Chegg's mission is to help students save time, save money and get smarter.

Subscribe: https://www.youtube.com/@chegg
TikTok: https://www.tiktok.com/@chegg
Instagram: https://www.instagram.com/chegg/
Twitter: https://twitter.com/chegg

00:00 Intro
00:38 Lewis model
01:13 Examples
01:50 Metal cations as acids


hey everybody, for today's problem we have a
reaction here that I've drawn, this is

this compound reacting with sulfuric
acid to generate this product, and what

we're gonna do is we want to show the
mechanism, that means every single

intermediate and every single electron
pushing arrow, so other than the fact that

we're reacting with with a strong acid i don't
want to give too much away

go ahead and give it a shot

ok so this is a pretty interesting
mechanism let's take a look at what

happens, now we know that this is a
strong acid, it has the capacity to

protonate something. the only thing we're
gonna be able to protonate is this hydroxyl

group so anytime you see an acid-base
reaction, we've got a strong acid, we know

that strong acid is gonna donate a proton so
we want to look at the substrate and say

where's the proton gonna go? well once
again the only thing here that's gonna

work, we have a lone pair on oxygen,
that's the only thing that can

accommodate a proton, so that is gonna
get protonated and now we have basically

a water molecule right here. now whereas
a hydroxyl group is a is a terrible

leaving group, a water molecule is a
great leaving group and we are in acidic

condition so positive charges are ok, so
this water can leave so that if

water leaves, now we're left with a carbocation right here. now this is the

key step, this is a carbocation
rearrangement step. if we remember from

the other lectures we can have a hydride
shift or we can have a methanide

shift where actual alkyl groups are
moving, but the interesting thing here is

that this is gonna be able to rearrange
to turn a secondary carbocation into a

tertiary carbocation and the way
it's going to be able to do it is with

this methanide shift right there. or
it's not really a methyl but an alkyl

shift where this bond is going to
detach from that carbon and reattach

to that carbon so this is what we're
gonna get. this is favorable for two

reasons

number one: we turn a secondary carbocation

into a tertiary carbocation so that's a driving force

but then the other thing we're doing is
turning a five-membered ring into a

six-membered ring, so there's a lot going
on here that makes this a favorable

rearrangement. and so now from the
secondary carbocation we have this

tertiary carbocation, and we are in aqueous acidic
solution so we can always eliminate and

what's going to happen is this can grab
this proton here and form the pi bond

there, and there's our product.

thanks for watching guys, subscribe to my
channel for more tutorials and as always

feel free to email me

Practice Problem: Mechanism - Acid Catalysis

For this one we need to know what happens to alcohols under acidic conditions. Beware of tricky carbocations!

Try all of the organic chemistry practice problems: http://bit.ly/ProfDaveOCPP

Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


let's try a practice problem regarding
enthalpy of vaporization. so the question

is how much heat is required to vaporize
1.500 liters of water at 37 degrees

Celsius so in order to answer this we
need to know that the density of water

at 37 degrees Celsius is actually just a
hair under one gram per milliliter which

is what we're used to we're going to use
point nine nine three four grams per

milliliter to be very specific and then
the heat of vaporization of water at 37

degrees Celsius is forty three point
four six kilojoules per mole so this is

all the data you need to answer this
question go ahead and give it a try.

let's take our one point five zero zero
liters of water and we're gonna want to

do some stoichiometric calculations so
we've got to get two moles our goal is

always going to be to get two moles
somehow with these things so let's take

our one point five zero zero liters and
we want milliliters because our density

was grams per milliliter so let's
multiply by a thousand milliliters over

one liter and we're gonna get 1,500
milliliters now that we have milliliters

we can use our density 1500 milliliters
times zero point nine nine three four

grams per milliliter and that is going
to give us a mass of fourteen ninety

grams so that is the mass of water
contained in that volume of water

specifically at this temperature 37
degrees Celsius right if we had a

different temperature things might be
slightly different then we take our

fourteen ninety grams of water and we're
gonna multiply by one mol / eighteen

point oh two grams that's the molar mass
of water and we know we therefore have

eighty two point six nine moles of water
that's how many moles of water are in

this volume of water at this temperature
then lastly we can just use the given

thermo chemical data we know that eighty
two point six nine moles times forty

three point four six kilojoules of
energy required per mole for

vaporization to occur that's going to
give us a total of three thousand five

hundred ninety four kilojoules of energy required to vaporize this volume of water at this temperature.

Practice Problem: Enthalpy of Vaporization

Can we do stoichiometry regarding phase changes? Sure! If we know how many moles of a substance we have, and the energy associated with each mole of that substance undergoing a particular phase change, we can get the energy associated with a specific sample undergoing that phase change. It's easy, try it!

Try all of the general chemistry practice problems: http://bit.ly/ProfDaveGCPP

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


[Music]

Professor Dave and CH here we just learned
about enantiomers so we know that they are

pairs of molecules which are non-identical mirror
images of one another but what does this have to

do with how molecules behave do entiers have any
different properties let's investigate given that

enantiomers are precise I mirror images they
have nearly identical physical properties they

have exactly the same density polarity melting
point and boiling point one way of distinguishing

between a pair of an antier has to do with the
direction that they rotate plain polarized light

when a beam of ordinary light passes through
something called a polarizer only the light

oscillating in a particular plane will pass
through and this is said to be plain polarized

as light oscillating along any other plane is
blocked out any chyal compound will be optically

active meaning that it will rotate plain polarized
light by some angle depending on the structure of

the molecule as measured by and analyzed on
the other side of the molecule with respect

to the light source when looking at a pair of an
anti immerse they will rotate this light by the

same angle but in opposite directions one will be
dextrorotatory signified with a plus sign meaning

the rotation is clockwise and the other will be
Lev rotatory signified with a minus sign meaning

the rotation is counterclockwise we can measure
the optical activity of many different compounds

and tabulate them and testing the optical
activity of a sample is a way of determining

the enantiomeric purity of the sample if both
enantiomers are present in equal amounts the

dexr rotatory and Lev rotatory activity will
cancel out and the sample will not be optic

active overall if one enantiomer is pure
it will rotate the light according to the

tabulated value for that enantiomer and then if
the optical activity is some fraction of that

of the pure en antier we can do math to find
out the ratio of one enantiomer to the other

in the sample and so we now have a little more
context surrounding the concept of an antier

in the way of a specific application namely a
physical property that differs from one in antier

to the other we can think of optically
active as more or less a synonym for

Kyu but we also now know exactly what the term
means Professor Dave for che see you next time

Enantiomers and Optical Activity Ft. Professor Dave

Now that we've learned about enantiomers—pairs of molecules that are non-identical mirror images of each other—let's learn what enantiomers can tell us about how molecules behave. With @ProfessorDaveExplains, we'll learn how enantiomers are distinguished by their optical activity: the ability to rotate plane-polarized light in different directions. We'll also learn how we can measure the particular degree of rotation of an optically active compound to determine its enantiomeric purity.

Get more homework help from Chegg at https://che.gg/3HbtG8Y
Watch the whole Organic Chemistry playlist: https://www.youtube.com/playlist?list=PLllCkartRRdMPnATf1X8qVdo5RzM8gA_M

About Chegg:
Chegg is a leading education technology company that provides students with affordable and accessible study resources. Chegg's mission is to help students save time, save money and get smarter.

Subscribe: https://www.youtube.com/@chegg
TikTok: https://www.tiktok.com/@chegg
Instagram: https://www.instagram.com/chegg/
Twitter: https://twitter.com/chegg

00:00 Intro
00:39 Plane-polarized light
01:01 Optical activity


Some of the important reactions in Organic Chemistry involve generating new carbon-carbon bonds.

Especially ones in which we add new alkyl groups to a benzene ring or some other aromatic structure.

So one of these reactions is the Friedel-Crafts Alkylation.

This is where we are able to add some alkyl fragment to a benzene ring or some other aromatic structure.

So what is happening here is we have a benzene ring and we have an alkyl chloride – could be any alkyl chloride.

I've drawn this one arbitrarily.

And then in the presence of aluminum trichloride, lewis acid catalyst, we're going to get this benzene ring with the alkyl substituent and then HCl byproduct.

So this actually operates in a very similar manner to the halogenation we just saw.

So once again the first step is one in which we're generating a catalytic intermediate.

So a lone pair on the chlorine atom is going to go and interact with the aluminum atom in the aluminum trichloride very similarly to the way we were seeing the iron compound behaving before.

And so we're going to generate this compound here.  Once again this chlorine is going to have a formal positive charge, because it is contributing 6 electrons to this lewis dot structure.

And then the aluminum atom will have a formal negative charge, because it is now contributing 4 electrons to this lewis dot structure.

Now the only difference here from the halogenation is that there is now a further step.

The benzene ring is not going to directly interact with this intermediate.

Instead what is going to happen is this carbon-chlorine bond is going to cleave and it's going to do so because it will then stabilize this chlorine atom and neutralize it and then we'll have an alkyl carbocation.

We'll have this alkyl cation intermediate instead. So now we have our isopropyl cation and then we have the remainder of the catalytic complex.

The aluminum will still have a formal negative charge there.  Aluminum has 3 valence electrons, here it is showing 4.  That means it has a formal negative charge.

So now this is a big difference because whereas a benzene ring would have a very difficult time interacting with this neutral chloroalkane, there's going to be a much lower activation energy associated with benzene interacting with this highly unstable carbocation.

The instability dictates it's going to be much more reactive and therefore able to react even with benzene.

So this pi bond is going to interact with the carbocation.

Now that alkyl fragment is attached to the ring just as we've seen before.

Now we have a cation on the ring and then the remainder of this structure

In order to neutralize this aluminum atom, the chlorine atom leaves with the electrons in this bond

Goes extracts the proton, the electrons left behind form the new pi bond

And we've restored aromaticity.  So now we have that alkyl fragment present on the benzene ring.

And then we have HCl and then we've regenerated the catalyst.

So this is extremely similar to the halogenation mechanism we just saw.

The only difference is that the benzene ring doesn't immediately react with this catalytic complex.

There is yet a second step where this carbon-chlorine bond cleaves generating a carbocation intermediate and it is the carbocation intermediate that interacts initially with the benzene ring.

Thanks for watching, guys.  Subscribe to my channel for more tutorials, and as always, feel free to email me with questions

Friedel-Crafts Alkylation

How do you attach alkyl groups to benzene rings? The Friedel-Crafts reaction is one way. This is one of the Electrophilic Aromatic substitutions we will examine.

Watch the whole Organic Chemistry playlist: http://bit.ly/ProfDaveOrgChem

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMath

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


in eukaryotes a number of proteins

called transcription factors must bind

to a promoter before RNA polymerase 2

can bind and initiate transcription the

first transcription factor to bind has

been named tf2d tf2d binds to a region

of the promoter called the tata box

which contains the sequence

ta ta T following tf2d binding a

succession of other transcription

factors and RNA polymerase to bind

forming an initiation complex although

this complex is often capable of

initiating transcription for many genes

other proteins are required for a high

rate of transcription in the promoter

there may be a region of DNA that can

bind to regulator proteins a regulator

protein binds to the regulator region

and to the transcription initiation

complex thereby activating it enhancer

regions are yet other transcriptionally

important regions on the DNA and they

are frequently located some distance

from the promoter often tens of

thousands of base pairs away activator

proteins bind to enhancers and then

attach to the transcription initiation

complex stimulating it strongly

if a cell has all of the appropriate DNA

sequences and if all the necessary

regulator proteins and transcription

factors are present and in place

transcription begins and the gene is

expressed otherwise no transcription or

very little transcription takes place

and the gene is silent

Initation of eukaryote Transcription


[Music]

hi everyone it's dr a and in this video

we're going to discuss a process

of bone growth and development called

intramembranous ossification

the first thing that i'd like to share

with you is that bone is a type of

replacement tissue

in other words bone tissue develops to

replace an existing tissue

and that existing tissue is known as

cartilage so we can think about

cartilage as a blueprint for the

building of bone tissue

so in this process we start with unique

specialized cells called mesenchymal

cells

and this type of cell is a precursor

cell for connective tissue

in other words it's this cell that leads

to the development of a variety of

connective tissues

and for the purposes of this video we're

going to utilize a green circle

to represent the mesenchymal cell

and it's through intramembranous

ossification

that we have the development of flat

bones like those of the skull

the ribs and the clavicle

so ultimately this process begins with

the embryonic skeleton and remember that

here we're starting with the cartilage

model

and in the cartilage we begin with

mesenchymal cells which gather together

these mesenchymal cells then

differentiate into specific connective

tissues

some of these differentiate into

capillaries and others become osteogenic

cells

and for note-taking purposes osteogenic

cells are the precursor cells meaning

that they ultimately become bone cells

now these osteogenic cells differentiate

and become osteoblast

and these osteoblasts appear as a

cluster of cells

and this cluster of cells is called or

referred to as an ossification center

these osteoblasts then secrete an

unmineralized material called osteoid

and although not pictured once this

osteoid is secreted it allows for the

deposit of collagen fibers into the

osteoid

and following this

we'll soon have the deposit of minerals

such as calcium and phosphorus which

allow the tissue to begin heartening

over the course of a few days

and through this process the

become entrapped in the surrounding

tissue

now what's unique to this process is

that in the areas where osteoid is

secreted around the capillaries it

becomes what we call trabecular bone

and as this process continues we'll end

up having two distinct portions

the outer portion of this bony tissue is

called the periosteum or compact bone

and again the inner portion which is

largely surrounded by capillaries is

referred to as trabecular bone

and this is the process of

intramembranous ossification in a

nutshell

well thank you for watching this video i

hope it's been helpful and if you indeed

found value in it please like comment

share and subscribe i'll look forward to

seeing you in the next video

you

Intramembranous Ossification

Intramembranous Ossification! What is Intramembranous Ossification? How does understanding this process of ossificaiton help me to better understand the body, and the skeleton? Let's make intramembranous ossification an easy process to figure out.


number four asks which of the marked

loan pairs on the following compound is

delocalized so what this is asking is is

there any loone pair on here such that

we could draw another resonance

structure by turning that loone pair

into a calent bond pushing some other P

electron density onto some other portion

of the molecule which one of these lone

pairs can be moved around essentially so

let's look at number one first we have

an oxygen we have two lone pairs there

is there anywhere that these can go can

we for example take this lone pair and

put it right there well we can't here

because this carbon already has four

bonds it's got a bond to oxygen two

bonds to these two carbon atoms there's

an implied hydrogen it is not going to

be able to accommodate any other bonds

we need access to other Pi electrons

that can Shuffle around in some other

way we have a pi Bond over here but

that's just too far away it's not going

to be able to interact with this one so

that's going to be no let's look at

number two we have a lone pair here is

it the case that this can go down here

well in this case it actually can

because this is adjacent to this Pi bond

this CN Sigma bond is adjacent to this

CC double bond which has a sigma and a

pi Bond so if we push this loan paired

down like that we can also take this Pi

Bond and push it right there and we

could put the anion on that carbon

instead we would end up with n plus and

C minus this is the case that this loone

pair is delocalized that is going to be

number two let's just look at the other

options with the Florine atom we've got

three lone pairs here is it the case

that we can take a lone pair and push it

there well no we can't because again

we've got a carbon atom here that's got

four bonds already it's not going to be

able to accommodate another Bond because

it cannot lose a bond the way that this

carbon atom did right this carbon atom

was able to accommodate a new Bond

because it was able to lose a bond as

well and remain coordinated with four

bonds there so this one can't do it

that's no good and then the same thing

here with oxygen this just isn't going

to work this oxygen could take one of

these piie bonds but we're not going to

form yet another Bond here because this

carbon has no bond that it can lose so

this also is not going to work again in

order for the lone pair to be

delocalized we have to be able to draw

another resonance structure like we did

here where this loone pair goes down we

form a pi Bond there and then we lose

that piie bond that flies up and gives

you the Ion on the carbon atom so that

one is going to be B lone pair number

two

Professor Dave Explains Delocalized Electrons #organicchemistry

Take Professor Dave's Structure and Bonding Organic Chemistry Exam here 👉 https://chemmunity.info/structureandbonding

💯Check out Professor Dave's Practice Exams and more OCHEM RESOURCES here: https://chemmunity.info/dave 🙌


so let's look at a problem
regarding isotopic abundance and atomic

mass. the question says the abundances of
the following silicon isotopes are as

follows: silicon 28 is ninety two point
two three percent, silicon 29 is four

point six seven percent, and silicon 30
is 3.10% so that means out of all the

silicon atoms in the universe ninety two
point two three percent of them weigh

twenty-eight atomic mass units, four
point six seven percent of them weigh

twenty nine atomic mass units, and three
point one zero percent of them weigh

thirty atomic mass units. so the question
is what is the average atomic mass of

silicon. so if this is confusing go and
check out my tutorial on nuclides

symbols, we want to understand atomic
mass we want to understand atomic number

and mass number and we want to
understand what isotopes are, so if you

are unclear go ahead and check out that
tutorial first, if everything makes sense give this a shot.

so here are the
relevant values, now what are we going to

do with them? as it turns out to get the
average atomic mass all we need to do is

multiply the mass number of each isotope
by its abundance, so let's do that now.

first we have silicon 28 so let's put 28
times zero point nine two two three

that is 92 point two three percent of
one, or a whole. to that we will add 29

for the mass number of silicon 29 and
multiply that by zero point zero four

six seven, that is four point six seven
percent of one or a whole, which

represents the atomic mass
of silicon. and lastly we have 30 for the

mass number of silicon 30 and we will
multiply that by zero point zero three

one zero, which is three point one zero
percent of one. and now all we need to do

is add these up. let's also be clear that
our answer should have three sig figs

because these values in the parentheses
have four sig figs, three sig figs, and

three sig figs respectively, so that will
limit our answer to three sig figs. and

if we plug all of that into a calculator
we do get 28 point one and that is the

average atomic mass of silicon that we
would find on the periodic table. so that

means if we took a sample of silicon
atoms and added all of their masses

together and then divided by the number
of atoms there are, we would get twenty

eight point one atomic mass units as the
average mass of all of those silicon atoms.

Practice Problem: Isotopic Abundance and Atomic Mass

In the general chemistry series we learned about nuclide symbols, which all imply a specific atomic number and mass number. Associated with this were isotopes, and average atomic mass. Given the relative abundances of all the isotopes of an element, how can we find the average atomic mass of that element? Let's practice that calculation here!

Try all of the general chemistry practice problems: http://bit.ly/ProfDaveGCPP

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


مرحبًا بكم في علم الأعصاب لمدة دقيقتين ، حيث أنا
شرح مبسط لموضوعات علم الأعصاب

في دقيقتين أو أقل. في هذه الدفعة
سأناقش إمكانية الغشاء.

يشير احتمال الغشاء إلى الفرق
في الشحنة الكهربائية بين الداخل والخارج

خارج الخلايا العصبية. هذه هي البلازما
أو غشاء الخلية العصبية. يفصل

داخل الخلية من البيئة الخارجية ؛
سنقول هذا هو الداخل وهذا

خارج العصبون. الاختلاف
في الشحنة الكهربائية يتطور بسبب التجمع

من أيونات داخل وخارج الغشاء.
الأيونات هي ذرات إما فقدت أو اكتسبت

وبالتالي تكون للإلكترونات موجبة أو سالبة
الشحنة.

هناك العديد من الأيونات التي تلعب دورًا مهمًا
دور في إمكانات الغشاء للخلايا العصبية.

هناك أيونات صوديوم ذات شحنة موجبة ،
ممثلة بهذه الدوائر الزرقاء وسلبية

أيونات الكلوريد المشحونة ، ممثلة بهذه
دوائر خضراء. عندما يكون العصبون في حالة استرخاء ، فإن الخلايا العصبية

أيونات الصوديوم وأيونات الكلوريد أكثر انتشارًا
خارج الخلية. هناك أيضا بشكل إيجابي

أيونات البوتاسيوم المشحونة ، ممثلة بهذه
الدوائر الصفراء ومختلف سالبة الشحنة

الأيونات ، وغالبًا ما يشار إليها باسم الأنيونات العضوية
ممثلة بهذه الدوائر الرمادية (أنيون

ببساطة مصطلح أيون سالبة الشحنة).
عندما يكون العصبون في حالة استراحة ، فإن أيونات البوتاسيوم

والأنيونات العضوية أكثر انتشارًا في الداخل
الخلية. في بقية الخلايا العصبية

أكثر سلبية من الخارج ،
مما يسبب احتمالية غشاء الراحة

يبلغ متوسط الخلايا العصبية حوالي -70 ملي فولت.

إحدى الطرق للحفاظ على هذه الإمكانات هي من خلال
آلية تعرف باسم الصوديوم والبوتاسيوم

مضخة. هذا بروتين نقل يستخدم
الطاقة لضخ باستمرار ثلاثة أيونات الصوديوم

للخروج من الخلية أثناء الضخ في نفس الوقت
اثنين من أيونات البوتاسيوم في الخلية. لان

يتم ضخ أيونات أكثر إيجابية
يساعد على الحفاظ على الغشاء

السلبية المحتملة.

على عكس الأيونات الأخرى ، يميل البوتاسيوم إلى التحرك
بسهولة إلى حد ما عبر غشاء الخلية من خلال

القنوات الأيونية ، والتي تمتد عبر الغشاء
البروتينات التي تسمح للأيونات بالمرور.

البوتاسيوم سيخرج من الخلايا العصبية حتى
يصل إلى النقطة التي يكون فيها في حالة توازن

- عندما لا تدفع قوى مثل الانتشار
في اتجاه أو آخر. في هذه

النقطة ، إمكانات الغشاء للخلايا العصبية
حول -65 إلى -70 mV ، والتي تعرف باسم

إمكانات الغشاء الباقي.

2-Minute Neuroscience: Membrane Potential

In my 2-Minute Neuroscience videos I explain neuroscience topics in 2 minutes or less. In this video, I discuss membrane potential. Membrane potential refers to the difference in charge between the inside and outside of a neuron, which is created due to the unequal distribution of ions on both sides of the cell membrane. Membrane potential is maintained through mechanisms like the sodium-potassium pump, and an understanding of membrane potential is crucial to understanding what happens during an action potential.

For more neuroscience articles, videos, and a complete neuroscience glossary, check out my website at www.neuroscientificallychallenged.com !

TRANSCRIPT:

Welcome to 2 minute neuro, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss membrane potential.

Membrane potential refers to the difference in electrical charge between the inside and outside of a neuron. This is the plasma or cell membrane of the neuron. It separates the inside of the cell from the outside environment; we’ll say this is the inside and this is the outside of the neuron. The difference in electrical charge develops due to the grouping of ions on the inside and outside of the membrane. Ions are atoms that have either lost or gained electrons and thus have a positive or negative charge.

There are a variety of ions found in the human body; several play an important role in the membrane potential of neurons. There are positively charged sodium ions, represented by these blue circles and negatively charged chloride ions, represented by these green circles. When a neuron is at rest, the sodium ions and chloride ions are more prevalent outside of the cell. There are also positively charged potassium ions, represented by these yellow circles and various negatively charged ions, often referred to as organic anions represented by these grey circles (anion is simply a term for a negatively charged ion). When a neuron is at rest, the potassium ions and organic anions are more prevalent inside the cell. At rest, the inside of the neuron is more negatively charged than the outside, causing the resting membrane potential of an average neuron to be around -70 mV.

One way this potential is maintained is through a mechanism known as the sodium-potassium pump. This is a transport protein that uses energy to constantly pump three sodium ions out of the cell while at the same time pumping two potassium ions into the cell. Because there are more positive ions being pumped out than negative, it helps to keep the membrane potential negative.

Unlike other ions, potassium tends to move fairly easily across the cell membrane through ion channels, which are membrane spanning proteins that allow ions to pass through. Potassium will pass out of the neuron until it reaches the point where it is at an equilibrium---when forces like diffusion aren’t pushing it in one direction or the other. At this point, the membrane potential of the neuron is around -65 to -70 mV, which is known as the resting membrane potential.

REFERENCE:

Purves D, Augustine GJ, Fitzpatrick D, Hall WC, Lamantia AS, McNamara JO, White LE. Neuroscience. 4th ed. Sunderland, MA. Sinauer Associates; 2008.


Hey guys, it’s Dave, if you’re here on
my Patreon page, it means that you’re considering

supporting me in my quest to educate the world.

I want to raise the bar of science literacy
in our society, and I sure could use your help.

Unlike some of the bigger educational channels,
I don’t have a staff, I don’t have any

grants or funding, this is a low-budget one-man show.

I write, edit, and animate all the content
on my channel, while managing all other aspects

of being an entrepreneur.

It’s a lot of work, and I’m usually at
it about sixty or seventy hours a week, so

calling it my passion is an understatement.

The problem is that the ad revenue I earn
from my YouTube channel is nowhere near commensurate

with the work I put in.

Even with tens of thousands of views per day,
it’s just not a living wage.

Beyond that, I have to pay people to check
my scripts for errors, operate camera and

audio when I shoot the content, and all kinds
of other things, so I sure could use some

help covering those costs.

If I can get enough support from you guys,
the viewers who benefit from all this hard

work, I can even hire people to help with
some of the writing and animating, which means

I could move much faster, and put out twice
as much content every week.

Even though I’ve already covered a lot of
topics, from chemistry to biology to physics

and tons more, there are still so many other
subjects left to do, and I’m not going to

stop until I do them all.

So please check out the rewards on this page.

For just a few dollars a month you can get
access to exclusive material, live chatting

with me, you can vote on what subjects I cover
next, or even get one-on-one tutoring.

These are just some of the ways I want to
thank you guys for taking the initiative to

help when you didn’t even have to, because
that’s how we are going to create the world

we all want to live in.

I’ll see you on YouTube.

Professor Dave Patreon Trailer

This is the trailer for my Patreon page. If you're watching it on YouTube, go to Patreon instead! And while you're there, please consider supporting me!

https://www.patreon.com/professordaveexplains


ok so for this problem we've got a
substrate here which has a ketone

functional group and a carboxylic acid
functional group and we're gonna do two

reactions with two different reducing
agents, we've got sodium borohydride and

we've got lithium aluminum hydride so if
you don't remember what these do go ahead and

check out my lecture on oxidation
reduction in the organic chemistry

playlist and we we these are going to
generate two different products based on

reducing capacity of these two reducing
agents so go and see if you can draw the

correct product for these two
transformations

we've got our two different reducing agents, our sodium
borohydride and a lithium

aluminum hydride, we know that those are
both sources of hydride, H- which is

going to act as a nucleophile and
attack a carbonyl and reduce some carbonyl

containing compound but the key
difference here is that sodium

borohydride is a softer reducing agent, a
bit weaker whereas lithium aluminum

hydride is a hard reducing agent, it's a little
bit stronger, so there is a

discrepancy in what kind of carbonyl
containing compounds they are able to

reduce. as it happens sodium borohydride is
only able to reduce ketones and

aldehydes, this is because the ketone
an aldehyde functional group, the partial

positivity on this carbonyl carbon
differs from that of say a carboxylic

acid because this carbon there, remember
that this adjacent oxygen atom is able to

put electrons onto that carbon via
resonance and so that is the reason that

this is not as partially positive and
therefore not as electrophilic as a ketone

or aldehyde carbon so that means that
just the discrepancy in electrophilicity

between this and this means that sodium
borohydride is able to reduce this

ketone functional group but not the
carboxylic acid functional group so as a

result on the product

reducing with sodium borohydride we can
see that the ketone has been reduced to

the secondary alcohol whereas the
carboxylic acid has been untouched

it does not have the ability to reduce the
carboxylic acid so that won't change

however lithium aluminum hydride is able
to reduce ketones, aldehydes, carboxylic

acids, esters, it is a stronger reducing
agent because it's stronger it is

able to reduce not just this but also
this and so as a result we can see in

the product that the ketone has been
reduced to the secondary alcohol just as

it has over here but in addition the
carboxylic acid has been reduced to the

primary alcohol. so the key here is
noticing the difference in reducing

strength of these two reducing agents and
using that information to draw the to

correct products

thanks for watching guys, subscribe to my
channel for more tutorials and as always

feel free to email me

Practice Problem: Reducing Agents

For this one we need to know the ability of different reducing agents to react with various functional groups.

Try all of the organic chemistry practice problems: http://bit.ly/ProfDaveOCPP

Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


number four asks a catalyst lowers the

blank for a reaction is it activation

energy change in entropy change in

enthalpy change in free energy if we are

looking at an energy diagram we have

reactants we have products this is going

to be the activation energy that's the

activation energy right there what a

catalyst does it is going to lower that

value it is going to lower the

activation energy so here's the new

activation energy there so this is going

to be a what we need to understand about

the catalyst is that it does not alter

any of these other parameters it does

not change the position of reactants or

products on the energy diagram for

example change in enthalpy or change in

free energy that is determined from

where the reactants sit to where the

products sit so if those don't change

their location none of those values can

change either all that we're changing is

the energy of the transition

What Does a Catalyst Do?

This is an abbreviated version of this question for YouTube Shorts. Check out the full version in the linked video.

Get $5 off your first month of Chemmunity with promo code: DAVE


hey all, it'sPprofessor Dave, I want to
continue talking about elimination reactions

specifically the E1 reaction.

so the E1 reaction is to the E2 reaction
as the SN1 reaction is to the SN2 reaction

so basically as you'd expect, the E1
reaction is going to be

two steps with a unimolecular transition state

just like with the SN1

the first step in the E1 reaction is
that the leaving group leaves

so let's take a look at this substrate
here the bromine is gonna leave

that leaves a tertiary carbocation,
now it's very very important to understand

that while this substrate, this carbon is

sp3 hybridized and therefore has
tetrahedral geometry

anytime a carbon that is sp3 hybridized

loses an electron domain, because
this bromine is leaving

with the electrons in that bond now this
carbon atom has only

three electron domains and anything surrounded by three electron domains will

exhibit trigonal planar geometry so it
is the case that this methyl group is now

flat in the board, this is now a flat
molecule with respect to the carbons

so there is a formal positive charge now

and so that means even a weak nucleophile like water can go ahead do an

acid-base reaction

and grab that proton, so here is oxygen

interacting with this proton and then

the electrons in this carbon-hydrogen
bond are the ones that go to form

the carbon-carbon pi bond in the product

thanks for watching, guys. subscribe to my
channel for more tutorials

and as always feel free to email me with questions

E1 Reaction

Here we examine the mechanism for the E1 reaction. Don't worry, it's just these four for now!

Watch the whole Organic Chemistry playlist: http://bit.ly/ProfDaveOrgChem

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMath

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


today we're gonna do some titration calculations

consider the following acid-base
reaction we have hydrochloric acid and

sodium hydroxide yielding sodium
chloride and water if 50 milliliters of

an HCl solution with unknown
concentration are titrated with zero

point two five zero molar sodium
hydroxide and then if it takes 35 point

two three milliliters of base to reach
the equivalence point what was the

concentration of the HCL solution so if
you're not sure how to approach this go

ahead and check out my tutorial on
titration and when you're ready give it a try.

so let's put our reaction up top and
then what we need to remember about the

equivalence point is that it is the
point where the moles of acid equals

moles of base so it is the point where
precisely all of the acid has been

neutralized by the base so it is telling
us something about stoichiometry when

the equivalence point is reached so
since we want to find out the moles of

acid let's find the moles of base so
let's take our volume of base we have

thirty five point two four milliliters
of base that were required to reach the

equivalence point and let's first
convert that into leaders so dividing by

a thousand milliliters we have 0.03 five
to four liters of Base to reach the

equivalence point now since we have the
concentration of that base we can

convert liters into moles so let's take
our liters of base and multiply by 0.25

zero multiplied not means that was zero
point zero zero eight eight one moles of

base that were required to reach the
point now we have to look at the

stoichiometric ratio the acid in the
base are in a one-to-one ratio so that

means if that many moles of base were
required to reach the equivalence point

then we multiply by one mole of acid
over one mole of base and we get that

same number of moles back for the acid
so when the equivalence point was

reached that many moles of base had
precisely neutralized that many moles of

acid and that is the number of moles of
acid that were in the solution initially

for the HCl solution so now all we have
to do is convert that many moles of acid

into a concentration and so
concentration is moles per liter so we

take our moles of acid and we divide by
0.0500 liters because we know we had

fifty point zero milliliters of acid we
knew the volume we just didn't know the

concentration so that many moles over
that many liters gives us 0.176 moles

per liter or point 176 molar HCl which
was the concentration of our unknown HCl solution.

Practice Problem: Titration Calculations

Titration is a way to do stoichiometry with acids and bases. The equivalence point tells us something about the moles of acid and base that are present in solution at that moment. And if we know one of those values, we can know the other. Let's calculate some unknown concentrations!

Try all of the general chemistry practice problems: http://bit.ly/ProfDaveGCPP

General Chemistry Tutorials: http://bit.ly/ProfDaveGenChem

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


مرحبا, البروفيسور ديف هنا
لنتحدث عن الارقام المعنوية

يحتاج البشر إلى توصيل تجاربهم مع بعضهم البعض

كم البعد بين مدينتين؟ متى حدث شيء ما

وكم من الوقت قبل أن يحدث مرة أخرى؟
 لهذا السبب طورنا

وحدات القياس
 يرتبط بعضها بالظواهر الطبيعية

مثل اليوم أو السنة
مبنية على حركة الأرض

لكن الكثير منها تعسفي مثل معظم وحدات الطول والكتلة

عندما نشارك في القياس يجب أن نكون على دراية ببعض الشروط

على سبيل المثال ، كم عدد الأشخاص في هذا الحشد؟
يمكن أن نقول

10,000؟
 ماذا عن 10,400 أو 10,472

يجب أن نكون حريصين على عدم إجراء تقديرات أكثر دقة

من سماحة قدرات القياس لدينا
لذلك عندما نستخدم أجهزة القياس

نحن نقدر رقم واحد فقط أبعد من مستوى الدقة

الكامن في الالة
هنا يمكننا تقدير

2.33 سم ولكن ليس 2.33481

لا يوجد لدينا امكانية الوصول إلى هذا المستوى من الدقة

لذلك سيكون لأي قياس كمية معينة

من الارقام المعنية

المرتبطة بها التي تعرض مدى دقتها

هنا القواعد لتحديد عدد الارقام المعنية في القيمة

واحد: أي رقم ليس صفرًا

يعتبر رقم معني

اثنان: الأصفار بين الأرقام الأخرى غير الصفرية

تعتبر ارقام معنية

ثلاثة: الأصفار الابتدائية، التي تأتي قبل أول رقم غير صفري

ليست ارقام معنية

وأربعة: الأصفار الزائدة ،الآتية

بعد آخر رقم غير صفري ، تكون معنية فقط إذا كانت أصفارًا عشرية

لذا فإن 10000 فقط لديه رقم واحد معني مما يعني أنه في الحقيقة تقريبا 10000

ليس عشرة آلاف بالضبط.
إذا أعدنا هذا الحشد نفسه وزاد عليه

شخص ما

هل يمكننا تقدير عشرة آلاف وواحد؟
لا ، لأننا قدّرنا رقما معنويا واحدًا فقط

لذلك أي شيء من 9500 إلى 10499

سيقترب من تقديرنا البالغ 10000.
عندما نقوم بالحسابات علينا أن نعير

انتباهنا الى عدد الارقام المعنية

إذا قمنا بإضافة أو طرح إجابتنا فسيحتوي على العديد من المنازل العشرية

كقيمة مع أقل عدد من المنازل العشرية

إذا قمنا بمضاعفة أو قسمة إجابتنا فسيكون لها نفس العدد من الارقام المعنية

كقيمة مع أقل عدد من الارقام المعنية

مهما كان جوابنا سيكون علينا التقريب لأعلى أو لأسفل

باتجاه الرقم المناسب.
5 أو أعلى يعني تقريب نحو الاعلى

أربعة أو أقل يعني التقريب نحو الاسفل.
دعونا نتحقق من مدى الاستيعاب

شكرا لمشاهدتكم
اشتركوا في قناتي للمزيد من الدروس

وكالعادة لا تترددو في مراسلتي عبر البريد الإلكتروني

Measurement and Significant Figures

When we take a measurement or make a calculation, how many digits do we use? There's rules, friend! You must obey the sig figs. Don't worry, learn all about them in this clip, and you'll be the coolest kid on the block.

Watch the whole General Chemistry playlist: http://bit.ly/ProfDaveGenChem

Study for the AP Chemistry exam with me: https://bit.ly/ProfDaveAPChem

Organic Chemistry Tutorials: http://bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: http://bit.ly/ProfDaveBiochem
Biology Tutorials: http://bit.ly/ProfDaveBio
Classical Physics Tutorials: http://bit.ly/ProfDavePhysics1
Modern Physics Tutorials: http://bit.ly/ProfDavePhysics2
Mathematics Tutorials: http://bit.ly/ProfDaveMaths

EMAIL► ProfessorDaveExplains@gmail.com
PATREON► http://patreon.com/ProfessorDaveExplains

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: https://amzn.to/2HtNpVH
Bookshop: https://bit.ly/39cKADM

Barnes and Noble: https://bit.ly/3pUjmrn
Book Depository: http://bit.ly/3aOVDlT


number one asks a reaction with a

negative value for the change in free

energy is referred to as exothermic

endothermic exergonic endergonic so what

are we talking about we're talking about

free energy so Gibbs free energy is

associated with Delta G and we're

looking for a negative value for this

change exothermic and endothermic these

relate to enp exothermic means Delta H

is negative and endothermic means Delta

H is positive so those are not the ones

that we're looking for exergonic and

endergonic are words that relate instead

to Delta G to Gibs free energy a

negative Delta G is referred to as an

exergonic reaction endergonic would be

Delta G is positive a negative value for

the change in Gibbs free energy that's

Delta g equals negative that is going to

be exonic

Enthalpy and Free Energy


number three asks which is the strongest

acid when we're talking about acid

strength what we need to understand is

that the strength of an acid is

proportional to the stability of the

conjugate base that sounds like a lot

but what we really mean here is that the

more stable the thing is that you get

the more readily the acid wants to

donate the proton meaning the stronger

the acid is so if we have HF HCL hbr hi

what are the conjugate bases of these

things what are we going to get if these

lose protons HF becomes F minus HCL

becomes CL minus hbr becomes BR minus

and hi becomes I minus so we get the

halide ions so now the question becomes

what is the relative stability of the

halide ions that are being produced now

what is the trend we want to look at

here what we understand is that the

Which is the Strongest Acid?

This is an abbreviated version of this question for YouTube Shorts. Check out the full version in the linked video.