datavorous/entrance-exam-dataset huggingface dataset:
Which of the following metals is used as a catalyst in Haber's process of ammonia synthesis?

Options:
A Cobalt
B Copper
C Zinc
D Iron

The correct answer is:
Iron

Solution:
Iron is used as a catalyst in Haber's process.

The Haber process, also called the Haber Bosch process, is the industrial implementation of the reaction of nitrogen gas and hydrogen gas. It is the main industrial procedure to produce ammonia and the catalyst used is iron with a suitable promoter like K2O, CaO, SiO2, and Al2O3.

Hence, Iron is used in the Haber cycle as a cheap catalyst because it allows in acceptable time to reach a reasonable yield

Topic: Chemistry, Alcohols Phenols and Ethers, AP EAMCET, AP EAMCET 2020 (23 Sep Shift 1)
Which of the following methods are not used to refine any metal?

(A) Liquation

(B) Calcination

(C) Electrolysis

(D) Leaching

(E) Distillation

Choose the correct answer from the options given below

Options:
A B and D only
B A,B,D and E only
C B,D and E only
D A,C and E only

The correct answer is:
B and D only

Solution:
Electrolytic refining is a technique that is used for the extraction and purification of metals that are obtained by refining methods. The impure metal is used as an anode and the pure metal is used a cathode. Soluble salt from the same metal is used an electrolyte.

Liquation process is used for the purification of the metal, which itself is readily fusible, but the impurities present in it are not, used for the purification of Sn and Zn, and for removing Pb from Zn-Aq alloy.

Leaching is a process widely used in extractive metallurgy where ore is treated with chemicals to convert the valuable metals within into soluble salts while the impurity remains insoluble.

Calcination is the process in which the ore of the metal is heated to high temperature in the absence or limited supply of air or oxygen.

Distillation: This method is used for the purification of metals which possess a low boiling point such as mercury and zinc.

Topic: Chemistry, General Principles and Processes of Isolation of Metals, JEE Main, JEE Main 2022 (27 Jul Shift 1)
Which of the following methods can be used to prepare an aldehyde from an alkene?

Options:
A Ozonolysis
B Hydroboration-oxidation
C Wurtz reaction
D Clemmensen reduction

The correct answer is:
Ozonolysis

Solution:
Ozonolysis
Explanation: Ozonolysis of alkenes cleaves the double bond and forms carbonyl compounds. If the alkene is terminal, ozonolysis will produce an aldehyde.

Topic: Chemistry, Alcohols Phenols and Ethers, JEE Main
Which of the following methods is used for the preparation of ketones from nitriles?

Options:
A Rosenmund reduction
B Friedel-Crafts acylation
C Clemmensen reduction
D Grignard reaction

The correct answer is:
Grignard reaction

Solution:
Grignard reaction
Explanation: Nitriles react with Grignard reagents to form imines, which upon hydrolysis yield ketones.

Topic: Chemistry, Alcohols Phenols and Ethers, JEE Main
Which of the following methods is used to prepare oxiranes from alkenes?

Options:
A Ozonolysis
B Hydrogenation
C Epoxidation
D Hydroboration

The correct answer is:
Epoxidation

Solution:
Epoxidation
Explanation: Epoxidation is the chemical reaction that converts alkenes to oxiranes (epoxides) by adding an oxygen atom to the carbon-carbon double bond.

Topic: Chemistry, Alcohols Phenols and Ethers, JEE Main
Which of the following mineral does not contain Al.

Options:
A Cryolite
B Mica
C Feldspar
D Fluorspar

The correct answer is:
Fluorspar

Solution:
Fluorspar (CaF2), Cryolite (Na3AlF6),
Feldspar (KAlSi3O8), mica (K2O.3Al2O3.6SiO2.2H2O)

Topic: Chemistry, General Principles and Processes of Isolation of Metals, JEE Main
Which of the following mineral elements is needed during the formation of the mitotic spindle, which accumulates in older leaves, and is involved in the normal functioning of the cell membrane?

Options:
A Fe
B S
C Ca
D Pd

The correct answer is:
Ca

Solution:
Calcium is necessary for the formation of spindle fiber during mitosis. It is an immobile element and is accumulated in older leaves and is involved in the normal functioning of the cell membrane. It is necessary for the formation of the middle lamella of plants where it occurs as calcium pectate. It is necessary for the growth of apical meristem and root hair formation. It acts as an activator of several enzymes, e.g., ATPase, succinic dehydrogenase, adenylate kinase, etc. Along with Na+ and K+ it maintains the permeability of plasma membrane.

Topic: Biology, Mineral Nutrition, NEET
Which of the following mineral ion is used in the activation of enzymes responsible for respiration and photosynthesis?

Options:
A Zn2+
B Mg2
C Na2+
D Ca2+

The correct answer is:
Mg2

Solution:
Enzymes are biocatalyst which speeds up the reaction of the process. It is absorbed by plants in the form of divalent Mg2+. It activates the enzymes of respiration, photosynthesis, and are involved in the synthesis of DNA and RNA. Magnesium is a constituent of the ring structure of chlorophyll and helps to maintain the ribosome structure.

Topic: Biology, Mineral Nutrition, NEET
Which of the following modulated signal has the best noise-tolerance ?

Options:
A
Long-wave

B
Short-wave

C
Medium-wave

D
Amplitude-modulated

The correct answer is:
Short-wave

Solution:
Short-wave has the best noise tolerance.

Topic: Physics, Communication System, JEE Main, JEE Main 2013 (25 Apr Online)
Which of the following molecular orbitals has two nodal planes

Options:
A $\sigma 2 s$
B $\pi 2 p_y$
C $\pi^* 2 p_y$
D $\sigma^* 2 p_x$

The correct answer is:
$\pi^* 2 p_y$

Solution:
$\pi^* 2 p_y$ has two nodal planes.

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main
Which of the following molecules acts as a Lewis acid ?

Options:
A $\left(\mathrm{CH}_3\right)_3 \mathrm{~N}$
B $\left(\mathrm{CH}_3\right)_3 \mathrm{~B}$
C $\left(\mathrm{CH}_3\right)_2 \mathrm{O}$
D $\left(\mathrm{CH}_3\right)_3 \mathrm{P}$

The correct answer is:
$\left(\mathrm{CH}_3\right)_3 \mathrm{~B}$

Solution:
$\left(\mathrm{CH}_3\right)_3 \mathrm{~B} \rightarrow$ is electron efficient compound, so behaves as Lewis acid.

Topic: Chemistry, Classification of Elements and Periodicity in Properties, NEET, NEET 2009 (Mains)
Which of the following molecules has two sigma $(\sigma)$ and two pi $(\pi)$ bonds?

Options:
A
$\mathrm{C}_2 \mathrm{H}_4$

B
$\mathrm{N}_2 \mathrm{~F}_2$

C
$\mathrm{C}_2 \mathrm{H}_2 \mathrm{Cl}_2$

D
$\mathrm{HCN}$

The correct answer is:
$\mathrm{HCN}$

Solution:

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main, JEE Main 2014 (12 Apr Online)
Which of the following molecules have zero dipole moment?

(I) gauche conformation of 1, 2-dibromoethane.

(II) anti conformation of 1, 2-dibromoethane.

(III) trans-1, 4-dibromocyclohexane

(IV) cis-1, 4-dibromocylohexane

(V) tetrabromomethane.

(VI) 1, 1-dibromocyclohexane

Options:
A I and II
B II, III and V
C II and V
D I, IV and VI

The correct answer is:
II, III and V

Solution:
(II) anti conformation of 1, 2-dibromoethane, µ=0
(III) trans-1, 4-dibromocyclohexane, µ=0
(V) tetrabromomethane, µ=0

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main
Which of the following molecules is expected to rotate the plane of plane polarized light?

Options:
A

B

C

D

The correct answer is:

Solution:
The plane of polarized light is rotated by optically active compound, i.e. it should be chiral.
So, (A) has, chiral $\mathrm{C-}$atom. So, it is optically active.
In (B), (C) and (D) plane of symmetry is present.
Hence, (A) is correct.

Topic: Chemistry, General Organic Chemistry, JEE Main, JEE Main 2007
Which of the following molecules is least resonance stabilized?

Options:
A
B
C
D

The correct answer is:

Solution:
In A,B,D entire ring involved in delocalisation and follow huckel rule of (4n+2)pi electrons. so, they are aromatic and are more stable.
While in C one carbon is sp3 so non planar. so, non aromatic and it is less stable.

Topic: Chemistry, General Organic Chemistry, JEE Main, JEE Main 2017 (02 Apr)
Which of the following molecules/ions does not contain unpaired electrons?

Options:
A
$\mathrm{O}_7^{2-}$

B
$\mathrm{B}_2$

C
$\mathrm{N}_2^{+}$

D
$\mathrm{O}_2$

The correct answer is:
$\mathrm{O}_7^{2-}$

Solution:
No Solution Available

Topic: Chemistry, Chemical Bonding and Molecular Structure, JEE Main, JEE Main 2006
Which of the following monosaccharide is a pentose

Options:
A Galactose
B Glucose
C Fructose
D Arabinose

The correct answer is:
Arabinose

Solution:
Arabinose is an aldopentose
$\mathrm{HOCH}_2-(\mathrm{CHOH})_3-\mathrm{CHO}$

Topic: Chemistry, Biomolecules, JEE Main
Which of the following most closely depicts the correct variation of the gravitation potential, V(r) with distance r due to a large planet of radius R and uniform mass density? (figures are not drawn to scale)

Options:
A
B
C
D

The correct answer is:

Solution:
At inside points (r<R), V=-GM2R33R2-r2. So at the centre, r=0⇒V=-32GMR . At outside points r>R, V=-GMr. At surface, V=-GMR. So the gravitational potential is non-uniform and negative.

Topic: Physics, Gravitation, JEE Main, JEE Main 2015 (11 Apr Online)
Which of the following muscular disorders is inherited?

Options:
A Tetany
B Muscular dystrophy
C Myasthenia gravis
D Botulism

The correct answer is:
Muscular dystrophy

Solution:
Muscular dystrophy is an autosomal dominant disorder that refers to a group of disorders that involve a progressive loss of muscle mass and consequent loss of strength. The most common form is Duchenne muscular dystrophy. It typically affects young boys, but other variations can strike in adulthood.
Muscular dystrophy is caused by genetic mutations that interfere with the production of muscle proteins that are needed to build and maintain healthy muscles. The causes are genetic.

Topic: Biology, Principles of Inheritance and Variation, NEET, NEET 2019 (All India)
Which of the following muscular disorders is inherited?

Options:
A Tetany
B Muscular dystrophy
C Myasthenia gravis
D Botulism

The correct answer is:
Muscular dystrophy

Solution:
Muscular dystrophy is an autosomal dominant disorder that refers to a group of disorders that involve a progressive loss of muscle mass and consequent loss of strength. The most common form is Duchenne muscular dystrophy. It typically affects young boys, but other variations can strike in adulthood.
Muscular dystrophy is caused by genetic mutations that interfere with the production of muscle proteins that are needed to build and maintain healthy muscles.
The causes are genetic.

Topic: Biology, Principles of Inheritance and Variation, NEET
Which of the following name formula combinations is not correct?

Options:
A
$\mathrm{K}_2\left[\mathrm{Pt}(\mathrm{CN})_4\right]$ - Potassium tetracyanoplatinate (II)

B
$\left[\mathrm{Mn}(\mathrm{CN})_5\right]^{2-}$ - Pentacyanomagnate (II) ion

C
$\mathrm{K}\left[\mathrm{Cr}\left(\mathrm{NH}_3\right)_2 \mathrm{Cl}_4\right]$ - Potassium diammine tetrachlorochromate (III)

D
$\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_4\left(\mathrm{H}_2 \mathrm{O}\right) \mathrm{I}\right] \mathrm{SO}_4$ - Magnetron value.

The correct answer is:
$\left[\mathrm{Mn}(\mathrm{CN})_5\right]^{2-}$ - Pentacyanomagnate (II) ion

Solution:
The correct IUPAC Name of $\left[\mathrm{Mn}(\mathrm{CN})_5\right]^{2-}$. Pentacyanomangnate (III).

Topic: Chemistry, Coordination Compounds, JEE Main, JEE Main 2014 (11 Apr Online)
Which of the following names of the organic compounds is not correctly written?

Options:
A
4-hydroxy-3-methoxy benzaldehyde
B
5-methyl cyclohexane carboxaldehyde
C
2-(2-chlorophenyl) ethanal
D CH2=CH-C||O-CH=CH2
penta-1, 4-dien-3-one

The correct answer is:
5-methyl cyclohexane carboxaldehyde

Solution:
3-methylcyclohexane carbaldehyde

Topic: Chemistry, General Organic Chemistry, JEE Main
Which of the following nitrogen containing compound does not give Lassaigne's test?

Options:
A Urea
B Phenyl hydrazine
C Glycene
D Hydrazine

The correct answer is:
Hydrazine

Solution:
Hydrazine $\left(\mathrm{NH}_2-\mathrm{NH}_2\right)$ have no carbon so does not show Lassaigne's test.

Topic: Chemistry, General Organic Chemistry, JEE Main, JEE Main 2024 (04 Apr Shift 1)
Which of the following noble gas does not have an octet of electrons in its outermost shell

Options:
A Neon
B Radon
C Argon
D Helium

The correct answer is:
Helium

Solution:
Helium has $1 s^2$ electronic configuration which means it has only 2 electrons on its outermost shell.

Topic: Chemistry, p Block Elements (Group 15, 16, 17 & 18), JEE Main
Which of the following nuclear fragments corresponding to nuclear fission between neutron $\left({ }_0^1 \mathrm{n}\right)$ and uranium isotope $\left({ }_{92}^{235} \mathrm{U}\right)$ is correct :

Options:
A ${ }_{56}^{144} \mathrm{Ba}+{ }_{36}^{89} \mathrm{Kr}+4{ }_0^1 \mathrm{n}$
B ${ }_{56}^{144} \mathrm{Ba}+{ }_{36}^{89} \mathrm{Kr}+3{ }_0^1 \mathrm{n}$
C ${ }_{56}^{140} \mathrm{Xe}+{ }_{38}^{94} \mathrm{Sr}+3{ }_0^1 \mathrm{n}$
D ${ }_{51}^{153} \mathrm{Sb}+{ }_{41}^{99} \mathrm{Nb}+3{ }_0^1 \mathrm{n}$

The correct answer is:
${ }_{56}^{144} \mathrm{Ba}+{ }_{36}^{89} \mathrm{Kr}+3{ }_0^1 \mathrm{n}$

Solution:
Balancing mass number and atomic number
${ }_{92}^{235} \mathrm{U}+{ }_0^1 \mathrm{n} \rightarrow{ }_{56}^{144} \mathrm{Ba}+{ }_{36}^{89} \mathrm{Kr}+3{ }_0^1 \mathrm{n}$

Topic: Physics, Nuclear Physics, JEE Main, JEE Main 2024 (04 Apr Shift 1)
Which of the following nuclear reactions will generate an isotope?

Options:
A
neutron particle emission

B
positron emission

C
$\alpha$-particle emission

D
$\beta$-particle emission

The correct answer is:
neutron particle emission

Solution:
${ }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X} \longrightarrow{ }_{\mathrm{Z}}^{\mathrm{A}-1} \mathrm{X}+{ }_0^1 \mathrm{n}$
Hence, (A) is correct.

Topic: Chemistry, d and f Block Elements, JEE Main, JEE Main 2007
Which of the following numbers is nearest to the probability that three randomly selected persons are born on three different days of the week?

Options:
A $0.7$
B $0.6$
C $0.5$
D $0.4$

The correct answer is:
$0.6$

Solution:
There are 7 days in a week. If 1 st person's birth day
falls on any day out of 7 . So, probability is $\frac{7}{7}$. Since birthday of second person will fall on any of the
remaining six days then its probability $=\frac{6}{7} .$ And,
birthday of 3rd person will fall on any of the remaining
5 days so, its probability $=\frac{5}{7}$
$\Rightarrow$ Probability that all three persons will have different day as their birthday
$=\frac{7}{7} \times \frac{6}{7} \times \frac{5}{7}=\frac{30}{49}=0.612 \approx 0.60$

Topic: Mathematics, Probability, NDA, NDA 2008 (Phase 1)
Which of the following on heating with aqueous $\mathrm{KOH}$, produces acetaldehyde ?

Options:
A
$\mathrm{CH}_3 \mathrm{COCl}$

B
$\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{Cl}$

C
$\mathrm{CH}_2 \mathrm{Cl} \mathrm{CH}_2 \mathrm{Cl}$

D
$\mathrm{CH}_3 \mathrm{CHCl}_2$

The correct answer is:
$\mathrm{CH}_3 \mathrm{CHCl}_2$

Solution:

Topic: Chemistry, Haloalkanes and Haloarenes, JEE Main, JEE Main 2009
Which of the following on reactions with nitrous acid, followed by treatment with NaOH produces a blue coluration?

Options:
A RCH2NO2
B R3CNO2
C R2CHNO2
D PhNO2

The correct answer is:
R2CHNO2

Solution:
R-C|H2NO2+O=N-OHâR-C|=NNO2 -OH+H2ONitrolic acidDissolve in NaOH to giveblood red colouration
R-C||R-RNO2 +HNO2â No reaction
Râ C | | R âH NO 2 +HOâN=Oâ Râ C | | R âN NO 2 =O+ H 2 O Pseudoâ nitrole Does not dissolve in NaOH, but gives blue colouration
PhNO2+HNO2â No reaction

Topic: Chemistry, Amines, JEE Main
Which of the following on thermal decomposition yields a basic as well as an acidic oxide ?

Options:
A
$\mathrm{NaNO}_3$

B
$\mathrm{KClO}_3$

C
$\mathrm{CaCO}_3$

D
$\mathrm{NH}_4 \mathrm{NO}_3$

The correct answer is:
$\mathrm{CaCO}_3$

Solution:
$\mathrm{CaCO}_3 \rightarrow \underset{\text { Basic }}{\mathrm{CaO}}+\underset{\text { Acidic }}{\mathrm{CO}_2}$

Topic: Chemistry, s Block Elements, JEE Main, JEE Main 2012 (Offline)
Which of the following on treatment with hot concentrated acidified KMnO4 gives 2-methylhexane -1,6-dioic acid as the only organic product?

Options:
A
B
C
D

The correct answer is:

Solution:

Topic: Chemistry, Carboxylic Acid Derivatives, JEE Main
Which of the following option correctly define the effects of cortisol on the given substrate?

Options:
A

Blood Glucose	Lipids	Proteins
Increase	Breakdown	Synthesis

B

Blood Glucose	Lipids	Proteins
Increase	Synthesis	Breakdown

C

Blood Glucose	Lipids	Proteins
Decrease	Synthesis	Synthesis

D

Blood Glucose	Lipids	Proteins

Increase	Breakdown	Breakdown

The correct answer is:

Blood Glucose	Lipids	Proteins

Increase	Breakdown	Breakdown

Solution:
Cortisol is the most important glucocorticoid that is mainly involved in carbohydrate metabolism. GCs stimulate gluconeogenesis, lipolysis, and proteolysis. These inhibit cellular uptake and utilization of amino acids. Cortisol also helps in maintaining the cardiovascular system and the kidney functions.

Topic: Biology, Chemical Coordination and Integration, NEET
Which of the following option correctly defines the function of sodium–potassium pump?

Options:
A Na+ and K+ out of the neuron
B Na+ and K+ into the neuron
C Na+ into the neuron andK+out of the neuron
D K+ into the neuron and Na+ out of the neuron

The correct answer is:
K+ into the neuron and Na+ out of the neuron

Solution:
Different types of ion channels are present on the neural membrane. These ion channels are selectively permeable to different ions. When a neuron is not conducting any impulse, i.e., resting, the axonal membrane is comparatively more permeable to potassium ions (K+) and nearly impermeable to sodium ions (Na+). Similarly, the membrane is impermeable to negatively charged proteins present in the axoplasm. Consequently, the axoplasm inside the axon contains a high concentration of K+ and negatively charged proteins and low concentration of Na+. In contrast, the fluid outside the axon contains a low concentration of K+, a high concentration of Na+ and thus forms a concentration gradient. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na+ outwards for 2 K+ into the cell.

Topic: Biology, Neural Control and Coordination, NEET
Which of the following option correctly describes the variation of the speed υ and acceleration 'a' of a point mass falling vertically in a viscous medium that applies a force F=-kυ , where 'k' is a constant, on the body? (Graphs are schematic and not drown to scale)

Options:
A
B
C
D

The correct answer is:

Solution:
a = (g - α v)
dv dt = g - α v
∫0vdvg-αv=∫0tdt⇒ℓng-αvg=-αt
v=v01-e-αta=dvdt=v0αe-αt=a0e-αt

Topic: Physics, Laws of Motion, JEE Main, JEE Main 2016 (09 Apr Online)
Which of the following option explains the correct function of cortisol?

Options:
A Reabsorption of Na+ and water and excretion of K+ and phosphate ions.
B To produce anti-inflammatory reactions
C To carry out glycolysis, lipogenesis, and proteolysis.
D To increase cellular uptake and utilization of amino acids.

The correct answer is:
To produce anti-inflammatory reactions

Solution:
Glucocorticoids stimulate gluconeogenesis, lipolysis, and proteolysis; and inhibit cellular uptake and utilization of amino acids. Cortisol is also involved in maintaining the cardiovascular system as well as the kidney functions. Glucocorticoids, particularly cortisol, produce anti-inflammatory reactions and suppress the immune response. Cortisol stimulates RBC production.

Topic: Biology, Chemical Coordination and Integration, NEET
Which of the following option is correct for given curve?

Options:
A xm∝P
B xm∝P2
C xm∝P1/2
D xm∝P0

The correct answer is:
xm∝P1/2

Solution:
According to the Freundlich adsorption isotherm, xm=Kp1n
Taking log on bot sides.
logxm=logK+1nlog⁡P
Slope =1n
Slope from graph =y2-y1x2-x1=24=12
or, 1n = 12
∴xm=Kp12
or xm∝p12

Topic: Chemistry, Surface Chemistry, JEE Main
Which of the following option is incorrect?

Options:
A ~pâ~qâ¡pâq
B pâ~qâ¡pâ~qâ§~qâp
C ~pâqâ¡~pâq
D ~p⇒qâ¡pâ§â¼q

The correct answer is:
~p⇔q≡~p⇒q

Solution:
Option (D) is a theorem, hence (D) is correct
For option (B), s↔t≡s→t∧t→s, hence (B) is correct
For option (A), ~p⇔~q≡p⇔~~q
≡p⟺q
Hence, (A) is correct
For option (C), ~p⇔q≡~p⇔q
Hence, option (C) is incorrect

Topic: Mathematics, Mathematical Reasoning, JEE Main
Which of the following options are correct for the reaction?

2Au(CN)2-(aq)+Zn(s)→2Au(s)+Zn(CN)42-(aq)

A. Redox reaction

B. Displacement reaction

C. Decomposition reaction

D. Combination reaction

Choose the correct answer from the options given below:

Options:
A A only
B A and D only
C A and B only
D C and D only

The correct answer is:
A and B only

Solution:
Gold is then extracted from this complex by displacement technique by using a more electropositive zinc metal.

In this method, zinc (Zn) acts as a reducing agent and it reduces Au + to Au and itself gets oxidized from Zn to Zn+2 ions which combine with CN- ions and form soluble complex, sodium tetracyanozincate (II).

2Au(CN)2- aq+Zn s→2Au s+Zn(CN)42- aq

Topic: Chemistry, Redox Reactions, JEE Main, JEE Main 2023 (06 Apr Shift 1)
Which of the following options correctly describes the trend in the thermal stability of carbonates of Group 2 elements?

Options:
A Increases down the group
B Decreases down the group
C Remains constant across the group
D Varies unpredictably across the group

The correct answer is:
Increases down the group

Solution:
Correct Option is : (A)
Increases down the group

Topic: Chemistry, s Block Elements, NEET
Which of the following options correctly represents the lung conditions in asthma and emphysema, respectively?

Options:
A Increased respiratory surface; Inflammation of bronchioles
B Increased number of bronchioles; Increased respiratory surface
C Inflammation of bronchioles; Decreases respiratory surface
D Decreased respiratory surface; Inflammation of bronchioles

The correct answer is:
Inflammation of bronchioles; Decreases respiratory surface

Solution:
Asthma is inflammation of bronchioles. Its symptoms include wheezing, coughing, and difficulty in breathing mainly during expiration.
Emphysema is inflammation or abnormal distension of the bronchioles or alveolar sacs of the lungs. Many of the septa between the alveoli are destroyed and much of the elastic tissue of the lungs is replaced by connective tissue. As a result, alveolar septa collapse and the surface area get greatly reduced.

Topic: Biology, Breathing and Exchange of Gases, NEET, NEET 2018
Which of the following options describes Kolbe’s reaction correctly?

Options:
A Kolbe's reaction involves the electrochemical reduction of carboxylic acids to form aldehydes.
B Kolbe's reaction is a process in which alkyl halides are treated with alcoholic sodium hydroxide to produce alcohols.
C When phenol is treated with sodium hydroxide, sodium phenoxide is produced. This sodium phenoxide when treated with carbon dioxide, followed by acidification, undergoes electrophilic substitution to give ortho-hydroxybenzoic acid as the main product. This reaction is known as Kolbe's reaction.
D Kolbe's reaction is a reaction in which two alcohols are combined in the presence of an acid catalyst to form an ether.

The correct answer is:
When phenol is treated with sodium hydroxide, sodium phenoxide is produced. This sodium phenoxide when treated with carbon dioxide, followed by acidification, undergoes electrophilic substitution to give ortho-hydroxybenzoic acid as the main product. This reaction is known as Kolbe's reaction.

Solution:
Correct Option is : (C)
When phenol is treated with sodium hydroxide, sodium phenoxide is produced. This sodium phenoxide when treated with carbon dioxide, followed by acidification, undergoes electrophilic substitution to give ortho-hydroxybenzoic acid as the main product. This reaction is known as Kolbe's reaction.

Topic: Chemistry, Alcohols Phenols and Ethers, NEET