Q
stringlengths 4
529
| video_name
stringlengths 11
11
| A
stringlengths 1
584
|
|---|---|---|
At 5:15, what is the difference btw the voltage of the battery and the voltage across the capacitor? I just can't seem to get the difference. An in-depth explanation with examples will be great. Thanks. | SIU_9SMd5q0 | When they are hooked together, there is no difference. |
4:43, will the bacteria still survive once all the oxygen is depleted? Since they require oxygen to perform cellular respiration, won't they also die off, meaning EVERYTHING is dead now in a dead zone? | AxaWXWd2pw4 | Yes, the bacteria will die too. But I guess the big deal is, The oxygen is depleted by respiration of the bacteria, which causes aquatic plants and fish to die, which causes even more oxygen to be consumed, and so on. So there is this bad positive feedback going on. Yes. Everything dies. It is literally, dead zone |
how does 1/k become k? @7:08 | x34OTtDE5q8 | If k is just an arbitrary constant, then it makes no difference whether you call it k or 1/k. |
At 3:37, why does he divide both sides by 10 and not 20? | x34OTtDE5q8 | he divides succesively by 10 and 2 |
After viewing what you explained at 10:31 Can you work a problem or explain a case where the temp increases as the pressure decreases and the volume is constant? | x34OTtDE5q8 | That is given by him .you can have your own certain volume as well . If willing ,you can change it , and then the problem becomes more difficult. |
At 2:20, Sal said P1V1=P2V2 assuming no work was done, but doesn't squeezing the box count as work? | x34OTtDE5q8 | Practically squeezing the box counts as a work but we have to assume that no work has been done. Or it can be taken as the particles were shifted from a larger box to a smaller box without changing the kinetic energy. |
@6:20. Why is it KE=nKT instead of KE=nT/K.
Here's my reasoning T=K*KE/n, then
nT=K*KE
nT/K=KE, right
What am I doing wrong? | x34OTtDE5q8 | K is just a constant. Do your equation. make a new constant, call it M, and definite it as the reciprocal of your K, so M =1/K. Now you have KE = nMT, right? But M is still just some constant, we can call it whatever we want. So let s rename it to K. KE = nKT. Ultimately if you have a constant, you can call it whatever you want. If you want to call it K, you can. If you want to call it 1/K, you can, because if K is a constant then 1/K is also a constant. |
At 2:25, Sal said that the relationship between pressure and volume is constant unless work is done by the system. How does the amount of work done by the system affect this relationship, exactly? | x34OTtDE5q8 | PV = nrT. If PV is going to change, that means T has to change. To change T requires energy. Energy requires work. |
At 3:41 to about 4:01 Mr. Khan divided both sides of the equation by 10 but he didn't divide 500 by 10, but 20 and 50, how come? | x34OTtDE5q8 | I wondered the same the math works however. |
At 3:30, Sal said meter cube is the same as L.
I am not sure, but isn't L the same as decimeter cube not meter cube? | x34OTtDE5q8 | You are correct in saying that 1 dm^3 = 1 L. I think what Sal was getting at was that the units of volume on both sides of the equation must be the same. He probably should have added the words after converting m^3 to L or something similar. |
in 6:57, how could he just switch 1/k to k like that? | x34OTtDE5q8 | If it is just an unknown constant, it does not matter whether you call it k or 1/k. |
At 1:07, Sal writes Pascal as N/m3, shouldn't it be N/m2? | x34OTtDE5q8 | Yes it should be N/m^2 |
i cant figure it out..why volume is increased, if you want more pressure...?? according to Boyle's law volume is inversely proportional to pressure... I Didn't GET IT FROM 9:34..? | x34OTtDE5q8 | haha...no need to answer,, i myself got it ... :D :D :) silly me!! |
In an intermediate step of forming an oxime: why doesn't the OH on the hydroxylamine form water and make a leaving group (as it already does with the double bonded O on the reactant)? approx @3:00 | gSzxeL64Cn0 | I think the N and the O are very similar in electronegativity, so the O can t pull out the electrons from the N. Hence, they stay stuck together. |
at 7:10 why doesn't the other nitrogen of the hydrozine react with another molecule of cyclohexanone resulting in R=N-N=R (where R=cyclohexane)? | gSzxeL64Cn0 | The lone pair on the NHâ group in the hydrazone RâC=N-NHâ is delocalized by resonance with the C=N bond, so it isn t as nucleophilic as the lone pair in HâN-NHâ itself. |
At 6:00 he says that these are stereoisomers of oximes.Are they enantiomers or other kind of stereoisomers? | gSzxeL64Cn0 | No, they ain t enantiomers because there is not a chiral Carbon. |
At 3:37 why does oxygen all of a sudden give away its 2 electrons to nitrogen? | gSzxeL64Cn0 | He is displaying the resonance stabilization, the electrons are actually delocalized throughout the molecule, but it is displayed as if the oxygen made a double bond with the nitrogen. |
8:45 Does that mean that convection only happens in the lithosphere and the asthenosphere? | hHteUIS0OFY | Convection happens in the upper mantle (asthenosphere). When these currents are strong enough, the move the lithospheric plates above causing plate tectonics. |
At 2:31, Sal said that you could drill the oceanic crust and reach the mantle. If we ever did that, would the lava meet the water and cover the opening by solidifying or will any other type of change in the earth's surface or a natural disaster occur? | hHteUIS0OFY | If we ever do that, we would die of the heat and pressure (magma can melt iron). And if we ever did that, the magma will mix with the water and from sulfur dioxide, which is poisonous and can form acid rain clouds. So basically, even if it sounds stupid, it will be natural disaster. |
At 0:20, if we start naming the compound from benzene ring, moving halfway and then towards right in the bottom carbon chain(which you actuay used) there would have been nine carbon i.e. nonane, will it be wrong? | CJzuu_k9Nv0 | It will be wrong. You first choose the longest continuous chain (nonane). Then you pick the highest priority group (OH) and number the chain from the end closest to that group. |
At 2:47 why isn't isn't it 3-octanol, like In the alcohol nomenclature video, instead of octan-3-ol? | CJzuu_k9Nv0 | 3-Octanol is acceptable, but the IUPAC preference is to put the locant (the number) as close as possible to the group it locates. |
At 5:37, why is it not called 4-bromo-3-nitroaniline? | CJzuu_k9Nv0 | Because counting to keep numbers low. |
At 4:30 he says "The cell doesn´t want viruses." Isn´t that partially false? There is a reason why those viruses exist, isn´t there? Or do most scientists think nowadays that it´s just a random joke of mother nature? There may be many situations in which viruses give a useful genetic code to the cell so it makes it better in some way, what do you think? | 0h5Jd7sgQWY | No, there is no reason why a virus would have to be useful to a cell in order for the virus to exist. THe virus will exist if it has a way to propagate. Whether that propagation is favorable or unfavorable to the host cell is not relevant. |
At 6:44, Sal says something about tRNA. What is tRNA? | 0h5Jd7sgQWY | tRNA stands for transcribed RNA. |
Wait , at 4:45, sal draws a cell that he later(5-10 sec) mentions that the othe two sides will merge, and the virus is consumed within the cell. What kind of cell did he draw, and what kind of cell does that | 0h5Jd7sgQWY | I think it might have been a white blood cell, which is what attacks problems it is alerted to within the body. |
in 19:05, what is that red thing on the white blood cell? | 0h5Jd7sgQWY | It s a red blood cell |
1:54 what s an icosehedran ? | 0h5Jd7sgQWY | It is a solid with twenty congruent faces which are all equilateral triangles. |
at 1:00 what is the taxonomy system | 0h5Jd7sgQWY | It s a system scientists use to classify and identify organisms. It s made up of different ranks from that go from least to most specific - domain, kingdom, phylum (division), class, order, family, genus, and species. |
so is virus life or not 23:17 | 0h5Jd7sgQWY | no, a virus is not alive cause it cannot reproduce without a host cell to do everything for it. |
at 16:06 it states the virus can take D.N.A. from the host sell to another organism, does this speed up evelution | 0h5Jd7sgQWY | When a virus takes DNA from a host cell and then brings it to another organism, all it s really doing is spreading the DNA of the original organism it was in. It may also spread the disease or whatever it is that the virus originally had. Its basically like when someone in your family gets a cold, and then the virus spreads and you get it too. |
At 19:18, I saw this big red thing on the side of the white blood cell. What was it? | 0h5Jd7sgQWY | I m not positive, but I think that it is a platelet. |
Can I say that viruses are a very useful tool of nature because they make DNA "jump"? Sal talks about it at 16:00. So this process is only possible because of viruses and make communication between DNA of different species possible, is that right? | 0h5Jd7sgQWY | A virus can not naturally transfer DNA from one organism to another. When the cell is destroyed and the viruses come out, they carry no DNA from the cell, just viral DNA. |
What is SARS? At 21:31, he mentions "SARS". When I looked up what SARS is, Google simply told me that SARS is a respiratory illness caused by a coronavirus.... what even is a coronavirus? | 0h5Jd7sgQWY | A corona virus is any virus that can cause a variety of illnesses in an animal or human, in this case SARS (severe acute respiratory syndrome) is a virus that affects the respiratory system, just in case you were wondering the symptoms for this illness are flu like and can cause pneumonia. |
At 3:15 ,Sal said that virus seems like life when in comes in contact with something living.
So....we must be having , like a million "dormant" viruses around us , also maybe on our window sill , which have not yet come into contact with a living thing , right? | 0h5Jd7sgQWY | Our existence to some extent is caused by Viruses. Viruses are constantly swarming into our bodies. Sometimes they make us sick; sometimes our immune systems vanquish them; and sometimes they become a part of ourselves. A type of virus called a retrovirus makes copies of itself by inserting its genes into the DNA of a cell. The cell then uses those instructions to make the parts for new viruses. HIV makes a living this way, as do a number of viruses that can trigger cancer. |
Sal said that 5-8% of us is virus so what part of our body is that 5-8%?
and if you don't get what i'm saying see for yourself -> 14:13 | 0h5Jd7sgQWY | no particular part, just all over |
I thought HIV was a virus that attacked cells, mainly white blood cells. Is that true? I wonder because you said otherwise at about 10:00 ish, and from what i know, aids is what is after HIV, could you help me understand? thanks. | 0h5Jd7sgQWY | You are correct, although at 10:00 he doesn t really go into it. Later, more at the 20:00 mark, he does show a picture of HIV infecting a white blood cell. Keep in mind that AIDS is the syndrome caused by HIV after you have lost too many white blood cells to stay healthy. |
At around 20:30, in the first picture (the colored one), what is the mass of pink stuff? | 0h5Jd7sgQWY | The picture is HIV infecting a cell, so the other cell is a T cell. It s hard to say what it is specifically because we don t know where in the body the picture is taken, but my guess is the pink mass could be any cell in the blood. |
good video. From 19:00 to about 20:00, can you clarify what is the red stringy mass on the left side in the white blood cell picture? | 0h5Jd7sgQWY | I don t believe that the red mass is a virus - HIV viruses are fairly large for viruses, and if they are the green particles, there is not a known virus the size of the red mass. To me, it resembles a platelet - but I m not positive. |
8:30 What happens to all the other matter in the cell when the membrane dissolves? | 0h5Jd7sgQWY | Usually other cells take it in as food, while some of it is just expelled from the body as waste. |
at about 3:51 can you explain how it is possible to have a 4 dimensional sphere with a 3 dimensional surface? Is it like the space / time continuum from Star Trek. and if you go one direction and reach the end you go back where you started? like a doughnut or Torus? | 0w9R_foNLrg | A 4-d sphere would have to have a 3-d surface Just like a 3d sphere has a 2-d surface We can t picture a 4-d sphere but we know that if you were on one then if you traveled for a long enough time in the direction you thought was a straight line, you would end up back where you started. |
At 9:09, david says force of kinetic energy is equal to coefficient of kinetic energy multiplied by the normal force. But how? Can you please post a derivation or a link where he explains it? | dclP0R2wf7g | This is a good question. I have been using this formula for quite some time and have never seen a derivation either. My best educated guess would be that it was experimentally determined, meaning physicists investigated the kinetic friction force and found that it was proportional to the normal force by some factor, and they named the factor the coefficient of kinetic friction. |
Why does David use the coefficient of kinetic friction at 9:04?And why is it miu? | dclP0R2wf7g | watch sal s vids about friction |
At 10:00 you say that the peguins of the same mass will have the same speed, but what about momentum? Isn't momentum dependent on mass? | dclP0R2wf7g | Momentum is mass * velocity. So it depends on mass as well as velocity. So if they have the same mass and velocity, they have the same momentum. Coming to the question, he says that penguins with same speed will travel the same distance no matter what the mass of the penguin is. |
At 4:24 How was jay certain that zn will lose 2 electrons? | kCM2mSb4qIU | +2 is the commonest oxidation state for Zn although other oxidation states are known. You have compounds such as ZnO, ZnCl2, Zn(NO3)2, Zn(OH)2, etc, where it has this oxidation state of +2. To get to an oxidation state of +2 requires a Zn atom to lose two electrons. |
At 3:25, he starts to write down the configuration for Zn [Ar]. Why does he ignore the p-block section of the periodic table. Shouldn't Zn [Ar] be: 1s2, 2s2, 2p6, 3s2, 3p6, 3d12 , not Zn [Ar]: 4s2, 3d10 ? | kCM2mSb4qIU | There are only five d orbitals per energy level, which can hold a maximum of 10 electrons. So [Ar] 4s2 3d10 is the correct electron configuration for zinc. The [Ar] here just represents the electron configuration of argon which is 1s2 2s2 2p6 3s2 3p6, so the full electron configuration of zinc is 1s2 2s2 2p6 3s2 3p6 4s2 3d10. |
When are you able to write the 4s shell before the 3d shell? Is this only the case with transition metals, or are their exceptions to the rule as seen in 2:34? | kCM2mSb4qIU | 4s fills before 3d in most atoms. It s the norm, but there are exceptions. |
in 3:19-3:29 they say zn is next to ar,? can someone explain | kCM2mSb4qIU | It s the short hand notation for writing electronic configuration where we reference to the nearest noble gas (in this case, Ar) and continue writing the rest of the electronic configuration from there. e.g. Mg is [Ne] 3s2 just search short hand notation electronic configuration on google and you ll find it |
At 3:42,I noticed you used a technique to calculate electrons in d-sub shell. Could you please tell me more about it?so i can use it onward. | kCM2mSb4qIU | All he was doing was counting along from Sc to Zn. Zn was the 10th in the row which means 10 d electrons. Note that these electrons go into the 3rd shell (3d) - the 4s subshell fills before the 3d. Likewise, 5s fills before 4d, etc. |
At 6:30 Sal said molecules bump into each other.on solids it's known as friction. In air drag. What's it called in water | CQYELiTtUs8 | It would also be drag in water, or fluid resistance . The term drag applies to fluid flow, which includes both air and water. The study of air flow would be aerodynamics, while the study of water flow would be hydrodynamics. |
At 1:30 Sal says that the rock will stay at rest but if a force is put upon that rock from all directions and equal force it will stay at rest like if it is mid air and equal force is put upon it from all directions will it stay in the air? | CQYELiTtUs8 | Yes, we call that picking up the rock. |
At 7:23 he said that in a world without gravity and air you can't stop anything but why in the space the things don't move in a line? | CQYELiTtUs8 | Gravity affects them, moving the thing into orbit around other objects, such as planets, stars, asteroids, etc.. Or these objects have a gravitational force that doesn t send the thing into orbit, but slightly alters their course, so they don t move in a straight line. |
At 23:00, according to newton's 1st law of motion object will be in the state of rest or in uniform motion in a straight line unless and until acted upon by any external unbalanced force. but motion is a relative term which depends on the observer or reference point so how does it became a law when it keeps changing depending on observer? It should be same in every aspect. | CQYELiTtUs8 | Any observer will see the object maintain its state of motion as that observer sees it. |
at 6:41 Salman says that the block of ice will bump into particles of air. Would aerodynamics elliminate the force of air? | CQYELiTtUs8 | Eliminate? No. Reduce? Yes. |
I thought that if something was thrown in a void, that that object would have a constant ACCELERATION,not velocity (0:38). My science teacher told me that if an asteroid was accelerating at 1 meters / seconds, it would continue to accelerate until some force stopped it. Is this true? | CQYELiTtUs8 | Acceleration is measured in meters / seconds*seconds, this is probably just a confusion between words. An asteroid can fly in constant acceleration only given strict condition: no gravity field and constant gas erruption from it, or a constant gravity field, which doesn t exist in that scales, only as aproximation. |
7:56
These laws then cannot be applied on earth where there is friction and gravity is acting upon every object. So then why do we still consider these laws? | CQYELiTtUs8 | They do apply. Friction and gravity are just additional forces to throw into the mix. |
At 7:18 Sal said the air particles will exert a pressure on the tennis ball as a reason it stops; then why doesn't it happen with light? | CQYELiTtUs8 | For something to be acted on by air resistance, it has to have mass. Photons, which light consists of, have no mass. They are simply little balls of energy, so they re not affected by air. |
At 5:12, Sal says everything comes to a stop. What about planets, or an asteroid? | CQYELiTtUs8 | Everything on earth comes to a stop, because of friction. If there s no friction, a moving object won t stop. Planets experience almost no friction, so they keep going. |
At 7:52 he says planets have a constant speed, is that the same for stars
I know Halleys comet moves much faster when its next to the sun and much slower when at its aphelion | CQYELiTtUs8 | interesting quesiton. As you know, the planets do not really have constant speed. But if we assume circular motion (which is an OK assumption) then the motion will be circular. As to whether stars have constant speed, it depend very much what the system is like where they belong. Does out Sun have a constant speed? What is your opinion? |
at 2:50 he says that if two people push with the same force the rock won't move, but where does that energy that those two people go to because it is not getting converted into friction since there is no movement.... so where does that energy go to | CQYELiTtUs8 | It doesn t really go anywhere, the forces cancel each other out and the people just get worn out. |
At 1:32, what about the gravitation forces applied on the rock by other objects present in the system like trees, other rocks, etc. ? | CQYELiTtUs8 | Good question! As is the case for many physics problem, we try to simplify our explanation by neglecting the effects that you are listing. Indeed, the gravitational pull from other objects is so incredibly small that we can forget about it. |
at 7:54 he says that the speed never changes on planets is that true because I heard somewhere that the earth moves a bit faster every year? | CQYELiTtUs8 | Earth s rotation is slowing down ever so slightly. So slightly that the change is immeasurable over the time that human civilization has been paying close attention to the length of a day. Earth s rate of revolution around the sun does not change in any measurable way. |
At 3:00 Sal mentions that the forces on the rock cancel each other out. What if there are slight differences in the forces? | CQYELiTtUs8 | Then the rock would move |
At 8:45 when we were talking about the plane example......we said that if the plane was moving or at rest and we were inside it, we wont realize that whether the plane is movinr or is at rest.......However even if the plane was accelerating with we being inside it......wont we still feel that we are at rest? Isn't it that both our velocity and the acceleration w.r.t. plane zero? | CQYELiTtUs8 | If the plane is accelerating, you will feel yourself pushed backward into your seat. This is because the plane has to exert a force on you to get you to accelerate along with it. Put a ball in a wagon and give the wagon a pull. See the ball appear to roll toward the back of the wagon? That s how the ball knows the wagon is accelerating. |
6:47 Does this mean that objects will not stop in space? Because there is no resistance in the void and no gravity either? | CQYELiTtUs8 | yes, that s why the earth keeps going around the sun and the moon keeps going around the earth. |
Also, at 3:40 in the video, isn't the ice at equilibrium?? Because all of its forces are at balance? | CQYELiTtUs8 | I guess you could say that. That s one of the several definitions of equilibrium =) |
9:20 Can't you tell if the plane turns? | CQYELiTtUs8 | This certainly is a great question,but according to me if you won t even feel the plane going so how can you tell the plane would turn,but in second case if we think that the plane takes a very very sharp turn we may feel as we also may move slightly on our seats Hope this helps. |
With the Airplane example 8:39 wouldn't you feel that the airplane was moving if it was falling? | CQYELiTtUs8 | You would only feel that you have become weightless inside the airplane (assuming the airplane is in free fall). NASA simulates zero-g by putting astronauts on a plane that flies a parabolic path so that it is descending at a free fall rate for short periods of time. They call it the Vomit Comet. |
6:56
Like you said there is going to be some amount of friction and the body in motion will eventually come to rest. So my question is why hasn't this law been changed or rephrased? | CQYELiTtUs8 | Friction is just another force. The law holds if you take the forces into account. There is nothing in the law that indicates you can ignore frictional forces. |
From 8:15 to 8:25, he says the ball would keep going on forever, so does that mean that if I were in space or vacuum and threw a ball it would go on forever?
The reference plane is also a little confusing to me. Because I'm in the plane and it is stationary from my point of view hence its difficult to tell whether the plane is moving, is that the concept? | CQYELiTtUs8 | yes that is what he meant because there is no gravity and so no force would be applied on the ball from the bottom.Thus it would go on forever ball stops because of frictional gravity but in vaccum where there is no gravity there is no force being applied on the ball.So it would never come down nad the second doubt of your s is not clear could you please explain it to me a bit more clearly? :) |
The ice will melt at 3:25 ... If you press on an ice cube on opposite sides, not only will it stay at rest, but it will melt. Where is the science behind that? Chemistry? | CQYELiTtUs8 | Water is one of the few liquids which expands when it freezes. When you apply pressure to ice, the melting point is lowered because the ice wants to revert back into a liquid in order to decrease its volume from the pressure. |
At 4:25, he mentions that an object will continue to move at a constant velocity unless it is acted upon by an external force. Won't an object only 'continue' to move like that if the surface it is moving on is frictionless? Otherwise the object would stop moving, wouldn't it? | CQYELiTtUs8 | Friction is caused by an external force pushing one object against another. I don t think a surface can really be frictionless, because friction is not really a property of an object. If an object really has no external force acting upon it, it will not be effected by friction and will continue at a constant velocity |
At 23:00, Sal said about the lattice structure of the water molecules,I didn't understood what it meant? Please explain | CQYELiTtUs8 | He s describing the bonds that hold the water in a solid shape and structure. As these lattice structures rub together, there will be friction between the pieces of ice. We perceive ice to be very slippery. That s because we usually experience it as a solid with a thin coat of liquid water. Liquid water experiences much less friction than solid water. If the temperature is cold enough to prevent our body heat and the pressure of our weight from melting the surface, ice is much less slippery. |
At 0:27, what does it mean by force impressed? | CQYELiTtUs8 | Being acted on by a force |
At 8:45, when Sal says that he'd have no idea if he was on a moving plane or a stationary one, is he still talking about Newton's first law or Einstein equivalence principle? Is Newton's first law analogous to it? Is it a direct consequence? Help! | CQYELiTtUs8 | newton I he is saying if there is no acceleration, i dont feel a force |
At 7:57 the comment corrects Sal saying he meant the objects never come to a stop rather than what he actually said which was they never slow down. Why is it incorrect to say they never slow down? (if there are no unbalanced forces to act on them in space?) | CQYELiTtUs8 | Because objects do slow down if they are not in a perfectly symmetrical orbit. (speeding up the closer you are, slowing down the further away). The correction is to distinct from slowing down vs stopping completely. |
At 6:27, when you gave the example of the ice cube moving on ice, you said that the molecules would bump and grind into each other, producing a little bit of heat. But then, wouldn't the heat cause the ice to melt, further lubricating the surface? The friction would have decreased then and it would continue moving, right? | CQYELiTtUs8 | Even if the ice melted enough to reduce the coefficient of friction, there is still friction. |
At 6:50-7:00, you said the ball would fall to the ground because of gravity but it would eventually stop because of friction. But, what if it was falling down an infinite hill wouldnât it gain speed no matter the amount of friction because it would be going downhill | CQYELiTtUs8 | Yes, in the absence of air resistance, a ball falling down an infinite hill would gain speed forever, according to Newton s laws. There is of course no such thing as an infinite hill but we can instead imagine a continuous accelerating force, which gives the same effect as an infinite hill). (We know now that the ball cannot exceed the speed of light, according to relativity, but we don t worry about that when we are working with Newtonian physics) |
@0:43, can someone explain to me why the N is positively charged? I mean if we count the electrons, we notice that the N has completed its octet, so why the positive charge? thank you. | rC165FcI4Yg | Yes, the N atom has an octet. But the rules for calculating formal charge say that the N atom owns only half of the shared electrons. Since it owns only 4 of the 8 shared electrons, it has officially lost one electron compared to what it has as an isolated atom. Its formal charge is therefore +1. |
@6:10 Jay is using the H2O molecule as a base instead of the HSO4-. Although the pKa of H3O+ is higher than that of H2SO4, would or wouldn't you recommend using HSO4-, as the catalyst is then showed to be "restored"? Or perhaps would you recommend to draw another reaction with a equilibrium to the left using H30+ and HSO4- to restore H2SO4? Is it generally considered to be ok (at exams) if you leave the recovery of the catalyst out? | rC165FcI4Yg | HâO is a stronger base than HSOââ», but either one can be used as the base. Many prof/teachers don t care if you don t show the regeneration of the catalyst, but many do care. Check with your own teacher to make sure of the policy. In this particular reaction, the HâSOâ is not regenerated, because it is a strong acid and reacts completely with the water to form HâO⺠and HSOââ». |
At 0:50, why doesn't the proton from H2SO4 get picked up by the oxygen with a -1 formal charge? Won't that happen instead, knowing that H+ will be more attracted to a greater negative charge? | rC165FcI4Yg | It does. It happens much more frequently than attack on the other oxygen. But all that does is regenerate the starting nitric acid starting material. It gets us nowhere. It is the few that get picked up by the other oxygen that lead eventually to the generation of the nitronium ion and nitrobenzene. |
at 0:50, why does the oxygen in the hydroxyl group share electrons with the hydrogen, and not the oxygen on the left that has a lone pair of electrons? | rC165FcI4Yg | Both protonated intermediates have a +1 formal charge. The âO- would indeed be more likely to pick up the proton, but then what? By which I mean that that is reversible, and either water or the conjugate base HSO4- would then deprotonate the H2NO3+, regenerating nitric acid. On the other hand, if the âOH is protonated, and it leaves as H2O, that reaction is less easily reversible, and the resulting nitronium ion has a chance to be attacked by benzene s Ï-bond. |
at 0:53, Why does the oxygen with no formal charge take the proton rather than the oxygen with a -1 formal charge? Is this just a trick to remember or can someone please further explain why this happens? | rC165FcI4Yg | The oxygen with the -1 formal charge is more strongly attracted to the + Nitrogen than the OH oxygen. Forming a diol is not favorable and the formation of a great leaving group in H2O leads to the protonation of the OH group instead of the -1 Oxygen. Protonation of the -1 Oxygen does happen but to keep neutrality the Hydrogen in the OH group is ejected and you end up with the starting product again. |
Why there is only one electron in the lone pair of O when Jay drew the structure @1:17?
There should be 2 electrons nah?? | rC165FcI4Yg | If you mean the top oxygen double bonded to the nitrogen, then yes. There s a missing electron. |
At 5:00, Jay draws in the formal charge on the nitrogen of the first resonance structure. What happens to this +1 formal charge? He doesn't show what happens and just names it as a nitro group. | rC165FcI4Yg | The + charge on N shows that N is the atom that will be attacked by the Ï electrons of the benzene ring. |
8:35, cleavages form during meiosis in animal cells. Plant cells will create cell plates and not create cleavage, right? | TX7-Kdn6lJQ | A cleavage furrow forms when an animal cell begins cytokenesis, while plant cells grow a cell plate that will eventually become the cell wall in the places where the cell split. |
At 2:30 in the chromosome picture the 23rd chromosomes are the same size, so does that mean that the person whose chromosomes these are is a girl? | TX7-Kdn6lJQ | Yup youre right Erin |
should it be Li2+ (2:21) | uVWquWFjnCw | No, it should be Li+, because Lithium is a Alkali metal and Alkali metals are in Group 1. Metals in group 1 give up 1 electron making its charge +. I hope that answers your question. |
At 5:50, you wrote that there was an increase in ionization energy due to the electron shielding that was occurring; however, at 5:13 you said that there was not much electron shielding occurring within the first shell between the two electrons. I need a little bit of clarification on whether the increase of ionization energy was really suppose to be due to the nuclear charge on that one magenta electron within the first shell or whether I am just mis-understanding electron shielding? | uVWquWFjnCw | This is not so. In the case of F and every atom. Every time with every successive electron taken away the Ionization energy goes up! |
At 4:48 he mentions that you get a nuclear charge of 1.3 when you do the "more complicated calculation". I realized he hasn't been showing us how to do this, anyone want to explain how he is getting a nuclear charge of 1.3? | uVWquWFjnCw | For that, we actually need to know the force and the angle at which it is exerted by the electrons in last shell and then the resultant of all the vectors of repulsion. We need to subtract this resultant from the charge of nucleus(atomic number). |
at 5:11, Sal says "it switches the direction of the current".
i know that change in magnetic poles occurs when the coil flips more than 90 degree which leads to reverse direction of current.
BUT WHY ? | XMkUDyl1ZRo | Because charges (eg electrons in a wire) experience a force when they move through a magnetic, and the direction of that force depends on the direction they are moving. |
Why Right Hand Rule @ 4:30 ?? | XMkUDyl1ZRo | yeah..but i thought the right hand rule was for induced current cases |
At 2:30 he's talking about sound waves. Does he mean that when the air molecules create areas of high and low pressure it creates sound waves? Or is there something I missed? | 6GB_kcdVMQo | Yes, sound waves propagate by oscillating air molecules, which create areas of high and low pressure as a result of the oscillations. |
At about 6:30, when referring to the carbon that is drawn in navy blue, why is this charge considered localized and why are there no resonance structures for it? Thanks in advance! | COZqJb-HT-k | You can t draw resonance structures for the structure with the carbon in blue, because the adjacent carbon atoms already have four bonds and a complete octet, so the pair of electrons are localized. That pair of electrons cannot be moved to form a double bond with the carbon in blue and one of the adjacent carbons, because any of these carbons would get five bonds, which cannot be. |
At 4:20, why does a carbon have -1 formal charge ? It is bonded to 2 hydrogen atoms and 2 carbon atoms so it's sharing 4 electrons, and 4-4=0. I don't get it, please help. :) | COZqJb-HT-k | It has 5 electrons: 1 from the H, 1 from each of the C atoms on either side of it, and the two lone pair electrons. 4 - 5 = -1 |
Regarding the Cyclopentanone around 6:00, how are the chances of it going through Keto-Enol tautomery? | COZqJb-HT-k | Keto-enlol tautomerization is actually a static process. In most cases, you will not see the enol-structure, cuz it is unstable. The product, in most cases, favors the keto-structure. So to me it is strange to ask about the chances , instead you make ask about the portion. |
At 4:02, Carole was mentioning a way of remembering things - She was saying A Banana with an orange hat juggling blueberries. This is a great example, but are there any more? | mlrOJgyPySw | That is a Mnemonic Device-Imagery, the best examples are ones that connect you to things that are familiar for you. |
At 7:00, from C to D work was done TO the system. Why did Sal say Work was done BY the system.
Work was done by the system from A to B, not from C to D.
Is this an error?
Also why is Q2 negative. | sPz5RrFus1Q | From C to D, work is done TO the system. That s the same as negative work being done ON the system. |
At 7:06, when Sal defines Q2 as the integral of P*deltaV, why isn't the P different from the P of Q1? Because it is very clear from the graph that the pressure at C and B are very different. | sPz5RrFus1Q | Good eye - P does vary throughout every process. It varies with V, so P is a function of V. This is why Sal s integral does NOT call P a constant and bring it out of the integral. Instead, he uses the ideal gas law to show that P varies according to 1/V (nRT/V) during the isothermal sections when T is constant, and plugs that into the integral, and gets the natural log of V as a result. Make sense? Then he plugs in the V values at A,B,C,D which as you pointed out are very different. |
Around 1:05 Sal says that in the second isothermic process (from C to D) you take away less heat than you needed to add in the first isothermic process (from A to B). Can anyone please help clarify why this is the case and why the heat added and taken are not the same? | sPz5RrFus1Q | The second isotherm is at a lower temperature and pressure, so it takes less work to compress it, and therefore less heat has to leave the system after the compression to keep the system at the same temperature (on that same lower isotherm). |
@4:55 Sal says "we'll see that Qsub2/Tsub2 is a negative value" which makes sense, but we never "see" that. We get to delta S =zero by ln1, not by demonstrating that the above represents a negative value which it must in order to get to zero. Please explain.
thx | sPz5RrFus1Q | Note that 0 = Îs = Q1 / T1 + Q2 / T2 â Q1 / T1 = âQ2 / T2. Does this make sense? |