NEET 2019 — Chemistry

All 42 Chemistry questions we hold from this paper, of the 176 on the site for this sitting — every option and the answer key. 4 marks each, −1 for a wrong answer.

Chemistry

45 questions, one correct option each. +4 for a correct answer, −1 for a wrong one, nothing for a blank.

Q1 open Hydrocarbons · Alkenes and alkynes: addition reactions, Markovnikov

The number of sigma ( $\sigma$ ) and pi ( $\pi$ ) bonds in pent-2-en-4-yne ( $\mathrm{CH_3\text{-}CH{=}CH\text{-}C{\equiv}CH}$ ) is:

A.10 $\sigma$ bonds and 3 $\pi$ bonds✓
B.8 $\sigma$ bonds and 5 $\pi$ bonds
C.11 $\sigma$ bonds and 2 $\pi$ bonds
D.13 $\sigma$ bonds and no $\pi$ bonds

The worked solution is part of a paid pack.

Q2 open Structure of Atom · Electronic configuration, Aufbau, Pauli, Hund

4d, 5p, 5f and 6p orbitals are arranged in order of decreasing energy. The correct option is:

A. $5f > 6p > 5p > 4d$ ✓
B. $6p > 5f > 5p > 4d$
C. $6p > 5f > 4d > 5p$
D. $5f > 6p > 4d > 5p$

The worked solution is part of a paid pack.

Q3 open Redox Reactions · Types of redox reactions

Which of the following reactions are disproportionation reactions?

(a) $2\mathrm{Cu^+ \to Cu^{2+} + Cu^0}$

(b) $3\mathrm{MnO_4^{2-} + 4H^+ \to 2MnO_4^- + MnO_2 + 2H_2O}$

(d) $2\mathrm{MnO_4^- + 3Mn^{2+} + 2H_2O \to 5MnO_2 + 4H^+}$

Select the correct option:

A.(a) and (b) only✓
B.(a), (b) and (c)
C.(a), (c) and (d)
D.(a) and (d) only

The worked solution is part of a paid pack.

Q4 open Thermodynamics · First law, enthalpy and Hess's law

Under isothermal conditions, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 2 bar. The work done BY the gas is: (Given: 1 L bar = 100 J)

A. $-30$ J
B.5 kJ
C.25 J
D.30 J✓

The worked solution is part of a paid pack.

Q5 open

Among the following, the one that is not a greenhouse gas is:

A.Nitrous oxide
B.Methane
C.Ozone
D.Sulphur dioxide✓

The worked solution is part of a paid pack.

Q6 open Electrochemistry · Electrochemical cells and Nernst equation

For the cell reaction $2\mathrm{Fe^{3+}(aq) + 2I^-(aq) \to 2Fe^{2+}(aq) + I_2(aq)}$ , $E^\ominus_{cell} = 0.24$ V at 298 K. The standard Gibbs energy ( $\Delta_r G^\ominus$ ) of the cell reaction is: (Given: Faraday constant $F = 96500\ \mathrm{C\,mol^{-1}}$ )

A. $-46.32\ \mathrm{kJ\,mol^{-1}}$ ✓
B. $-23.16\ \mathrm{kJ\,mol^{-1}}$
C. $46.32\ \mathrm{kJ\,mol^{-1}}$
D. $23.16\ \mathrm{kJ\,mol^{-1}}$

The worked solution is part of a paid pack.

Q7 open Biomolecules · Proteins, enzymes and vitamins

Enzymes that utilise ATP in phosphate transfer require an alkaline earth metal (M) as a cofactor. M is:

A.Be
B.Mg✓
C.Ca
D.Sr

The worked solution is part of a paid pack.

Q8 open Hydrocarbons · Alkenes and alkynes: addition reactions, Markovnikov

The most suitable reagent for converting but-2-yne ( $\mathrm{H_3C\text{-}C{\equiv}C\text{-}CH_3}$ ) into cis-2-butene is:

A.Na / liquid $\mathrm{NH_3}$
B. $\mathrm{H_2}$ , Pd/C, quinoline (Lindlar's catalyst)✓
C.Zn/HCl
D. $\mathrm{Hg^{2+}/H^+}$ , $\mathrm{H_2O}$

The worked solution is part of a paid pack.

Q9 open The p-Block Elements · Group 15 and 16: nitrogen, oxygen families

Which is the correct thermal stability order for $\mathrm{H_2E}$ (E = O, S, Se, Te, Po)?

A. $\mathrm{H_2S < H_2O < H_2Se < H_2Te < H_2Po}$
B. $\mathrm{H_2O < H_2S < H_2Se < H_2Te < H_2Po}$
C. $\mathrm{H_2Po < H_2Te < H_2Se < H_2S < H_2O}$ ✓
D. $\mathrm{H_2Se < H_2Te < H_2Po < H_2O < H_2S}$

The worked solution is part of a paid pack.

Q10 open The p-Block Elements · Group 13 and 14 elements

Which of the following is an incorrect statement?

A. $\mathrm{PbF_4}$ is covalent in nature✓
B. $\mathrm{SiCl_4}$ is easily hydrolysed
C. $\mathrm{GeX_4}$ (X = F, Cl, Br, I) is more stable than $\mathrm{GeX_2}$
D. $\mathrm{SnF_4}$ is ionic in nature

The worked solution is part of a paid pack.

Q11 open The p-Block Elements · Group 15 and 16: nitrogen, oxygen families

Match the following industrial processes with their principal product, and choose the correct option:

Column I	Column II
(a) Pure nitrogen	(i) Chlorine
(b) Haber process	(ii) Sulphuric acid
(c) Contact process	(iii) Ammonia
(d) Deacon's process	(iv) Sodium/barium azide

A.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
B.(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
C.(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
D.(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)✓

The worked solution is part of a paid pack.

Q12 open Chemical Bonding and Molecular Structure · Molecular orbital theory

Which of the following diatomic molecular species has only $\sigma$ bonds according to Molecular Orbital Theory?

A. $\mathrm{O_2}$
B. $\mathrm{N_2}$
C. $\mathrm{C_2}$ ✓
D. $\mathrm{Be_2}$

The worked solution is part of a paid pack.

Q13 open Classification of Elements and Periodicity in Properties · Periodic trends: radius, ionisation enthalpy, electron gain enthalpy, electronegativity

For the second-period elements, the correct increasing order of first ionisation enthalpy is:

A. $\mathrm{Li < Be < B < C < N < O < F < Ne}$
B. $\mathrm{Li < B < Be < C < O < N < F < Ne}$ ✓
C. $\mathrm{Li < B < Be < C < N < O < F < Ne}$
D. $\mathrm{Li < Be < B < C < O < N < F < Ne}$

The worked solution is part of a paid pack.

Q14 open

The biodegradable polymer among the following is:

A.Nylon-6,6
B.Nylon-2-nylon-6✓
C.Nylon-6
D.Buna-S

The worked solution is part of a paid pack.

Q15 open Equilibrium · Solubility product and common-ion effect

The pH of a saturated solution of $\mathrm{Ca(OH)_2}$ is 9. The solubility product ( $K_{sp}$ ) of $\mathrm{Ca(OH)_2}$ is:

A. $0.5 \times 10^{-15}$ ✓
B. $0.25 \times 10^{-10}$
C. $0.125 \times 10^{-15}$
D. $0.5 \times 10^{-10}$

The worked solution is part of a paid pack.

Q16 open Chemical Kinetics · Integrated rate equations and half-life

If the rate constant for a first-order reaction is $k$ , the time $t$ required for 99% completion of the reaction is given by:

A. $t = 0.693/k$
B. $t = 6.909/k$
C. $t = 4.606/k$ ✓
D. $t = 2.303/k$

The worked solution is part of a paid pack.

Q17 open Biomolecules · Proteins, enzymes and vitamins

The non-essential amino acid among the following is:

A.Valine
B.Leucine
C.Alanine✓
D.Lysine

The worked solution is part of a paid pack.

Q18 open Hydrocarbons · Aromatic hydrocarbons: electrophilic substitution, directing effects

Among the following, the reaction that proceeds through electrophilic substitution is:

A.Benzenediazonium chloride + $\mathrm{Cu_2Cl_2}$ $\to$ chlorobenzene + $\mathrm{N_2}$ (Sandmeyer reaction)
B.Benzene + $\mathrm{Cl_2}$ , $\mathrm{AlCl_3}$ $\to$ chlorobenzene + HCl (Friedel–Crafts halogenation)✓
C.Benzene + $\mathrm{Cl_2}$ , UV light $\to$ benzene hexachloride (free-radical addition)
D.Benzyl alcohol + HCl, heat $\to$ benzyl chloride + $\mathrm{H_2O}$

The worked solution is part of a paid pack.

Q19 open Solutions · Concentration terms, Henry's and Raoult's laws

The mixture that forms a maximum-boiling azeotrope is:

A.Water + nitric acid✓
B.Ethanol + water
C.Acetone + carbon disulphide
D.Heptane + octane

The worked solution is part of a paid pack.

Q20 open Chemical Kinetics · Rate law, order and molecularity

For the chemical reaction $\mathrm{N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$ , the correct expression relating the rates of disappearance/appearance of each species is:

A. $\dfrac{1}{3}\dfrac{d[H_2]}{dt} = \dfrac{1}{2}\dfrac{d[NH_3]}{dt}$
B. $\dfrac{d[N_2]}{dt} = 2\dfrac{d[NH_3]}{dt}$
C. $-\dfrac{d[N_2]}{dt} = \dfrac12\dfrac{d[NH_3]}{dt}$ ✓
D. $3\dfrac{d[H_2]}{dt} = 2\dfrac{d[NH_3]}{dt}$

The worked solution is part of a paid pack.

Q21 open Some Basic Concepts of Chemistry · Stoichiometry and limiting reagent

The number of moles of hydrogen molecules required to produce 20 moles of ammonia through the Haber process is:

A.10
B.20
C.30✓
D.40

The worked solution is part of a paid pack.

Q22 open Organic Chemistry: Some Basic Principles and Techniques · Electronic effects: inductive, resonance, hyperconjugation

The compound that is most difficult to protonate (at the carbonyl oxygen) among the following is:

A.Formaldehyde, $\mathrm{HCHO}$
B.Acetaldehyde, $\mathrm{CH_3CHO}$
C.Acetone, $\mathrm{CH_3COCH_3}$
D.Benzaldehyde, $\mathrm{C_6H_5CHO}$ ✓

The worked solution is part of a paid pack.

Q23 open Solutions · Concentration terms, Henry's and Raoult's laws

For an ideal solution, the correct option (at constant $T$ and $P$ ) is:

A. $\Delta_{mix}S = 0$
B. $\Delta_{mix}V \neq 0$
C. $\Delta_{mix}H = 0$ ✓
D. $\Delta_{mix}G = 0$

The worked solution is part of a paid pack.

Q24 open Equilibrium · Ionic equilibrium: acids, bases, pH, buffers

The conjugate bases for the Brønsted acids $\mathrm{H_2O}$ and $\mathrm{HF}$ are, respectively:

A. $\mathrm{OH^-}$ and $\mathrm{H_2F^+}$
B. $\mathrm{H_3O^+}$ and $\mathrm{F^-}$
C. $\mathrm{OH^-}$ and $\mathrm{F^-}$ ✓
D. $\mathrm{H_3O^+}$ and $\mathrm{H_2F^+}$

The worked solution is part of a paid pack.

Q25 open

Among the following, the narrow-spectrum antibiotic is:

A.Penicillin G✓
B.Ampicillin
C.Amoxycillin
D.Chloramphenicol

The worked solution is part of a paid pack.

Q26 open Hydrocarbons · Alkenes and alkynes: addition reactions, Markovnikov

An alkene A, on ozonolysis (reaction with $\mathrm{O_3}$ followed by Zn/ $\mathrm{H_2O}$ ), gives propanone and ethanal in equimolar amounts (A is 2-methylbut-2-ene). Addition of HCl to A gives B as the major product (Markovnikov addition). The structure of B is:

A. $\mathrm{Cl\text{-}CH_2\text{-}CH_2\text{-}CH(CH_3)_2}$
B. $\mathrm{H_3C\text{-}CH_2\text{-}CH(CH_2Cl)\text{-}CH_3}$
C. $\mathrm{H_3C\text{-}CH_2\text{-}C(Cl)(CH_3)\text{-}CH_3}$ ✓
D. $\mathrm{H_3C\text{-}CH(Cl)\text{-}CH(CH_3)_2}$

The worked solution is part of a paid pack.

Q27 open Coordination Compounds · Valence bond and crystal field theory

What is the correct electronic configuration of the central metal ion in $\mathrm{K_4[Fe(CN)_6]}$ , based on crystal field theory?

A. $t_{2g}^4 e_g^2$
B. $t_{2g}^6 e_g^0$ ✓
C. $e^3 t_2^3$
D. $e^4 t_2^2$

The worked solution is part of a paid pack.

Q28 open Chemical Bonding and Molecular Structure · VSEPR and molecular shapes

Identify the incorrect statement related to $\mathrm{PCl_5}$ from the following:

A.The three equatorial P–Cl bonds make an angle of $120^\circ$ with each other
B.The two axial P–Cl bonds make an angle of $180^\circ$ with each other
C.Axial P–Cl bonds are longer than equatorial P–Cl bonds
D. $\mathrm{PCl_5}$ molecule is non-reactive✓

The worked solution is part of a paid pack.

Q29 open Equilibrium · Ionic equilibrium: acids, bases, pH, buffers

Which of the following mixtures will make a basic buffer?

A.50 mL of 0.1 M NaOH + 25 mL of 0.1 M $\mathrm{CH_3COOH}$
B.100 mL of 0.1 M $\mathrm{CH_3COOH}$ + 100 mL of 0.1 M NaOH
C.100 mL of 0.1 M HCl + 200 mL of 0.1 M $\mathrm{NH_4OH}$ ✓
D.100 mL of 0.1 M HCl + 100 mL of 0.1 M NaOH

The worked solution is part of a paid pack.

Q30 open Aldehydes, Ketones and Carboxylic Acids · Carboxylic acids: acidity and reactions

The major product of strongly heating phthalic acid (benzene-1,2-dicarboxylic acid) with $\mathrm{NH_3}$ is:

A.Phthalic acid monoamide (o- $\mathrm{C_6H_4(COOH)(CONH_2)}$ )
B.Phthalimide (cyclic imide)✓
C.o-Toluic acid
D.o-Phenylenediamine

The worked solution is part of a paid pack.

Q31 open The p-Block Elements · Group 17 and 18: halogens, noble gases

Match the xenon compounds in Column I with their molecular geometry in Column II:

Column I	Column II
(a) $\mathrm{XeF_4}$	(i) Pyramidal
(b) $\mathrm{XeF_6}$	(ii) Square planar
(c) $\mathrm{XeOF_4}$	(iii) Distorted octahedral
(d) $\mathrm{XeO_3}$	(iv) Square pyramidal

A.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
B.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)✓
C.(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)
D.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)

The worked solution is part of a paid pack.

Q32 open The d- and f-Block Elements · Potassium dichromate and permanganate

The manganate ( $\mathrm{MnO_4^{2-}}$ ) and permanganate ( $\mathrm{MnO_4^-}$ ) ions are tetrahedral, due to:

A. $\pi$ -bonding involving overlap of p-orbitals of oxygen with d-orbitals of manganese✓
B.The absence of any $\pi$ -bonding
C. $\pi$ -bonding involving overlap of p-orbitals of oxygen with p-orbitals of manganese
D. $\pi$ -bonding involving overlap of d-orbitals of oxygen with d-orbitals of manganese

The worked solution is part of a paid pack.

Q33 open The p-Block Elements · Group 13 and 14 elements

Which of the following species is not stable?

A. $[\mathrm{SiF_6}]^{2-}$
B. $[\mathrm{GeCl_6}]^{2-}$
C. $[\mathrm{Sn(OH)_6}]^{2-}$
D. $[\mathrm{SiCl_6}]^{2-}$ ✓

The worked solution is part of a paid pack.

Q34 open Electrochemistry · Electrochemical cells and Nernst equation

For a cell involving one electron transfer, $E^\circ_{cell} = 0.59$ V at 298 K. The equilibrium constant for the cell reaction is: (Given: $\dfrac{2.303RT}{F} = 0.059$ V at $T=298$ K)

A. $1.0 \times 10^2$
B. $1.0 \times 10^5$
C. $1.0 \times 10^{10}$ ✓
D. $1.0 \times 10^{30}$

The worked solution is part of a paid pack.

Q35 open

Which of the following is an amphoteric hydroxide?

A. $\mathrm{Sr(OH)_2}$
B. $\mathrm{Ca(OH)_2}$
C. $\mathrm{Mg(OH)_2}$
D. $\mathrm{Be(OH)_2}$ ✓

The worked solution is part of a paid pack.

Q36 open

A gas at 350 K and 15 bar has a molar volume 20% smaller than that for an ideal gas under the same conditions. The correct statement about the gas and its compressibility factor ( $Z$ ) is:

A. $Z>1$ and attractive forces are dominant
B. $Z>1$ and repulsive forces are dominant
C. $Z<1$ and attractive forces are dominant✓
D. $Z<1$ and repulsive forces are dominant

The worked solution is part of a paid pack.

Q37 open

A compound is formed by cation C and anion A. The anions form a hexagonal close-packed (hcp) lattice and the cations occupy 75% of the octahedral voids. The formula of the compound is: