JEE Main > Electrochemistry

Explore popular questions from Electrochemistry for JEE Main. This collection covers Electrochemistry previous year JEE Main questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

Conductivity (unit Siemen's S) is directly proportional to area of the vessel and the concentration of the solution in it and is inversely proportional to the length of the vessel then the unit of the constant of proportionality is

A

{tex} \mathrm { Sm }\ \mathrm { mol } ^ { - 1 } {/tex}

{tex} \mathrm { Sm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

C

{tex} \mathrm { S } ^ { - 2 } \mathrm { m } ^ { 2 } \mathrm { mol } {/tex}

D

{tex} \mathrm { S } ^ { 2 } \mathrm { m } ^ { 2 } \mathrm { mol } ^ { - 2 } {/tex}

Explanation

Q 2.    

Correct4

Incorrect-1

EMF of a cell in terms of reduction potential of its left and right electrodes is

A

{tex} E = E _ { \mathrm { left } } - E _ { \mathrm { right } } {/tex}

B

{tex} E = E _ { \mathrm { left } } + E _ { \mathrm { right } } {/tex}

{tex} E = E _ { \text {right } } - E _ { \text {left } } {/tex}

D

{tex} E = - \left( E _ { \text {right } } + E _ { \text {left } } \right) {/tex}

Explanation

Q 3.    

Correct4

Incorrect-1

What will be the emf for the given cell
{tex} \mathrm { Pt } \left| \mathrm { H } _ { 2 } \left( \mathrm { P } _ { 1 } \right) \right| \mathrm { H } ^ { + } ( \mathrm { aq } ) | | \mathrm { H } _ { 2 } \left( \mathrm { P } _ { 2 } \right) | \mathrm { Pt } {/tex}

A

{tex} \frac { R T } { F } \log _ { \mathrm { e } } \frac { P _ { \mathrm { l } } } { P _ { 2 } } {/tex}

{tex} \frac { R T } { 2 F } \log _ { e } \frac { P _ { 1 } } { P _ { 2 } } {/tex}

C

{tex} \frac { R T } { F } \log _ { \mathrm { e } } \frac { P _ { 2 } } { P _ { 1 } } {/tex}

D

None of these.

Explanation

Q 4.    

Correct4

Incorrect-1

Which of the following reaction is possible at anode?

{tex} 2 \mathrm { Cr } ^ { 3 + } + 7 \mathrm { H } _ { 2 } \mathrm { O } \rightarrow \mathrm { Cr } _ { 2 } \mathrm { O } _ { 7 } ^ { 2 - } + 14 \mathrm { H } ^ { + } {/tex}

B

{tex} \mathrm { F } _ { 2 } \rightarrow 2 \mathrm { F } ^ { - } {/tex}

C

{tex} ( 1 / 2 ) \mathrm { O } _ { 2 } + 2 \mathrm { H } ^ { + } \rightarrow \mathrm { H } _ { 2 } \mathrm { O } {/tex}

D

None of these.

Explanation


Q 5.    

Correct4

Incorrect-1

When the sample of copper with zinc impurity is to be purified by electrolysis, the appropriate electrodes are

A

Cathode - pure zinc {tex} \quad {/tex} Anode - pure copper

B

Cathode - impure sample {tex} \quad {/tex} Anode - pure copper

C

Cathode - impure zinc {tex} \quad {/tex} Anode - impure sample

Cathode -pure copper {tex} \quad {/tex} Anode - impure sample.

Explanation

Q 6.    

Correct4

Incorrect-1

Which of the following is a redox reaction?

A

{tex} \mathrm { NaCl } + \mathrm { KNO } _ { 3 } \rightarrow \mathrm { NaNO } _ { 3 } + \mathrm { KCl } {/tex}

B

{tex} \mathrm { CaC } _ { 2 } \mathrm { O } _ { 4 } + 2 \mathrm { HCl } \rightarrow \mathrm { CaCl } _ { 2 } + \mathrm { H } _ { 2 } \mathrm { C } _ { 2 } \mathrm { O } _ { 4 } {/tex}

C

{tex} \mathrm { Mg } ( \mathrm { OH } ) _ { 2 } + 2 \mathrm { NH } _ { 4 } \mathrm { Cl } \rightarrow \mathrm { MgCl } _ { 2 } + 2 \mathrm { NH } _ { 4 } \mathrm { OH } {/tex}

{tex} \mathrm { Zn } + 2 \mathrm { AgCN } \rightarrow 2 \mathrm { Ag } + \mathrm { Zn } ( \mathrm { CN } ) _ { 2 } {/tex}

Explanation



Q 7.    

Correct4

Incorrect-1

For a cell reaction involving a two-electron change, the standard e.m.f. of the cell is found to be {tex} \mathrm {0.295 V } {/tex} at {tex} 25 ^ { \circ } \mathrm { C } {/tex} . The equilibrium constant of the reaction at {tex} 25 ^ { \circ } \mathrm { C } {/tex} will be

A

{tex} 29.5 \times 10 ^ { - 2 } {/tex}

B

{tex}10{/tex}

{tex} 1 \times 10 ^ { 10 } {/tex}

D

{tex} 1 \times 10 ^ { - 10 } {/tex}

Explanation



Q 8.    

Correct4

Incorrect-1

Standard reduction electrode potentials of three metals {tex} \mathrm { A } , \mathrm { B } {/tex} {tex} \& \mathrm { C } {/tex} are respectively {tex} + 0.5 \mathrm { V } , - 3.0 \mathrm { V } \& - 1.2 \mathrm { V } . {/tex} The reducing powers of these metals are

A

{tex} \mathrm { A > B > C} {/tex}

B

{tex} \mathrm { C } > \mathrm { B } > \mathrm { A } {/tex}

C

{tex} \mathrm { A > C > B} {/tex}

{tex} \mathrm {B > C > A} {/tex}

Explanation


Q 9.    

Correct4

Incorrect-1

When during electrolysis of a solution of AgNO{tex}_3{/tex}, 9650 coulombs of charge pass through the electroplating bath, the mass of silver deposited on the cathode will be

{tex}10.8\ \mathrm g {/tex}

B

{tex}21.6\ \mathrm g {/tex}

C

{tex}108\ \mathrm { g } {/tex}

D

{tex}1.08\ \mathrm { g } {/tex}

Explanation



Q 10.    

Correct4

Incorrect-1

For the redox reaction:
{tex} \mathrm { Zn } ( \mathrm { s } ) + \mathrm { Cu } ^ { 2 + } ( 0.1 \mathrm { M } ) \rightarrow \mathrm { Zn } ^ { 2 + } ( 1 \mathrm { M } ) + \mathrm { Cu } ( \mathrm { s } ) {/tex}
taking place in a cell, {tex} \mathrm { E } _ { \text {cell } } ^ { \circ } {/tex} is 1.10 volt. {tex} \mathrm { E } _ { \text {cell } } {/tex} for the cell will be
{tex} \left( 2.303 \frac { \mathrm { RT } } { \mathrm { F } } = 0.0591 \right) {/tex}

A

1.80 volt

1.07 volt

C

0.82 volt

D

2.14 volt

Explanation


Q 11.    

Correct4

Incorrect-1

Several blocks of magnesium are fixed to the bottom of a ship to

A

make the ship lighter

prevent action of water and salt

C

prevent puncturing by under-sea rocks

D

keep away the sharks

Explanation

Q 12.    

Correct4

Incorrect-1

In a hydrogen-oxygen fuel cell, combustion of hydrogen occurs to

A

produce high purity water

create potential difference between two electrodes

C

generate heat

D

remove adsorbed oxygen from electrode surfaces

Explanation

Q 13.    

Correct4

Incorrect-1

Consider the following {tex} \mathrm { E } ^ { \circ } {/tex} values
{tex} \mathrm { E } ^ { \circ } _ { \mathrm { F } _ { \mathrm { e } } ^ { 3 + } / \mathrm { Fe } ^ { 2 + } } = + 0.77 \mathrm { V } ; \, \mathrm { E } _ { \mathrm { Sn } ^ { 2 + } / \mathrm { Sn } } ^ { \circ } = - 0.14 \mathrm { V } {/tex}
Under standard conditions the potential for the reaction
{tex} \mathrm { Sn } _ { ( \mathrm { s } ) } + 2 \mathrm { Fe } ^ { 3 + }_{ ( \mathrm { aq } )} \rightarrow 2 \mathrm { Fe } ^ { 2 + } _{( \mathrm { aq } )} + \mathrm { Sn } ^ { 2 + } _{( \mathrm { aq } ) }{/tex} is

{tex}0.91\,\ \mathrm { V } {/tex}

B

{tex}1.40\, \mathrm { V } {/tex}

C

{tex}1.68\, \mathrm { V } {/tex}

D

{tex}0.63\, \mathrm { V } {/tex}

Explanation




Q 14.    

Correct4

Incorrect-1

The standard e.m.f. of a cell involving one electron change is found to be 0.591{tex} \mathrm { V } {/tex} at {tex} 25 ^ { \circ } \mathrm { C } {/tex} . The equilibrium constant of the reaction is {tex} \left( \mathrm { F } = 96,500 \mathrm { C } \mathrm { mol } ^ { - 1 } ; \mathrm { R } = 8.314 \mathrm { JK } ^ { - 1 } \mathrm { mol } ^ { - 1 } \right) {/tex}

{tex} 1.0 \times 10 ^ { 10 } {/tex}

B

{tex} 1.0 \times 10 ^ { 5 } {/tex}

C

{tex} 1.0 \times 10 ^ { 1 } {/tex}

D

{tex} 1.0 \times 10 ^ { 30 } {/tex}

Explanation



Q 15.    

Correct4

Incorrect-1

The limiting molar conductivities {tex} \Lambda ^ { \circ } {/tex} for {tex} \mathrm { NaCl } , \mathrm { KBr } {/tex} and {tex} \mathrm { KCl } {/tex} are {tex} 126,152 {/tex} and {tex}150\, \mathrm { S } \mathrm { cm ^ { 2 } mol ^ { - 1 }} {/tex} respectively. The {tex} \Lambda ^ { \circ } {/tex} for NaBr is

A

{tex}278\, \mathrm { Scm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

B

{tex}176\, \mathrm { Scm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

{tex}128\, \mathrm {Scm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

D

{tex}302\, \mathrm { Scm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

Explanation




Q 16.    

Correct4

Incorrect-1

In a cell that utilises the reaction
{tex} \mathrm { Zn } _ { ( \mathrm { s } ) } + 2 \mathrm { H } ^ { + } ( \mathrm { aq } ) \rightarrow \mathrm { Zn } ^ { 2 + } ( \mathrm { aq } ) + \mathrm { H } _ { 2 ( \mathrm { g } ) } {/tex} addition of {tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } {/tex} to cathode compartment, will

increase the {tex} \mathrm { E } {/tex} and shift equilibrium to the right

B

lower the {tex} \mathrm { E } {/tex} and shift equilibrium to the right

C

lower the {tex} \mathrm { E } {/tex} and shift equlibrium to the left

D

increase the {tex} \mathrm { E } {/tex} and shift equilibrium to the left

Explanation





Q 17.    

Correct4

Incorrect-1

The {tex} \mathrm { E } ^ { \circ }_{ \mathrm { M } ^ { 3 + } / \mathrm { M } ^ { 2 + } }{/tex} values for {tex} \mathrm { Cr } , \mathrm { Mn } ,\mathrm { Fe } {/tex} and {tex} \mathrm { Co }{/tex} are {tex} - 0.41 , + {/tex} {tex} 1.57 , + 0.77 {/tex} and {tex} + 1.97 \mathrm { V } {/tex} respectively. For which one of these metals the change in oxidation state from {tex} + 2 {/tex} to {tex} + 3 {/tex} is easiest?

A

{tex} \mathrm { Fe } {/tex}

B

{tex} \mathrm { Mn } {/tex}

{tex} \mathrm { Cr } {/tex}

D

{tex} \mathrm { Co } {/tex}

Explanation

Q 18.    

Correct4

Incorrect-1

For a spontaneous reaction the {tex} \Delta G, {/tex} equilibrium constant (K) and {tex} E^\circ _ { \text {Cell } } {/tex} will be respectively

A

{tex} - \mathrm { ve } , > 1 , - \mathrm { ve } {/tex}

B

{tex} - \mathrm { ve } , < 1 , - \mathrm { ve } {/tex}

C

{tex} + \mathrm { ve } , > 1 , - \mathrm { ve } {/tex}

{tex} - \mathrm { ve } , > 1 , + \mathrm { ve } {/tex}

Explanation


Q 19.    

Correct4

Incorrect-1

The highest electrical conductivity of the following aqueous solutions is of

{tex}0.1\, \mathrm { M } {/tex} difluoroacetic acid

B

{tex}0.1\, \mathrm { M } {/tex} fluoroacetic acid

C

{tex}0.1\, \mathrm { M } {/tex} chloroacetic acid

D

{tex}0.1\, \mathrm { M } {/tex} acetic acid

Explanation


Q 20.    

Correct4

Incorrect-1

Aluminium oxide may be electrolysed at {tex} 1000 ^ { \circ } \mathrm { C } {/tex} to furnish aluminium metal (At. Mass {tex} = 27 \mathrm { amu } ; 1 {/tex} Faraday {tex} = 96,500 {/tex} Coulombs). The cathode reaction is {tex} - A l ^ { 3 + } + 3 e ^ { - } \rightarrow A l ^ { \circ } {/tex}
To prepare 5.12 {tex} \mathrm { kg } {/tex} of aluminium metal by this method we require

A

{tex} 5.49 \times 10 ^ { 1 } {/tex} C of electricity

B

{tex} 5.49 \times 10 ^ { 4 } {/tex} C of electricity

C

{tex} 1.83 \times 10 ^ { 7 } {/tex} C of electricity

{tex} 5.49 \times 10 ^ { 7 } {/tex} C of electricity

Explanation


Q 21.    

Correct4

Incorrect-1

{tex} \begin{array} { | c | c | c | c | c | c | c| } \hline \text { Electrolyte: } & { \mathrm { KCl } } & { \mathrm { KNO } _ { 3 } } & { \mathrm { HCl } } & { \mathrm { NaOAc } } & { \mathrm { NaCl } } \\ \hline \Lambda ^ { \infty} \ ( \mathrm { Scm } ^ { 2 } \mathrm { mol } ^ { - 1 }): & {149.9 } & { 145 } & { 426.2 } & { 91 } & { 126.5 } \\ \hline \end{array} {/tex}

Calculate {tex} \Lambda _ { \text {HOAc } } ^ { \infty } {/tex} using appropriate molar conductances of the electrolytes listed above at infinite dilution in {tex} \mathrm { H } _ { 2 } \mathrm { O } {/tex} at {tex} 25 ^ { \circ } \mathrm { C } {/tex}

A

217.5

390.7

C

552.7

D

517.2

Explanation




Q 22.    

Correct4

Incorrect-1

Which of the following chemical reactions depict the oxidizing beahviour of {tex} \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } ? {/tex}

A

{tex} \mathrm { NaCl } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \longrightarrow \mathrm { NaHSO } _ { 4 } + \mathrm { HCl } {/tex}

B

{tex} 2 \mathrm { PCl } _ { 5 } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \longrightarrow 2 \mathrm { POCl } _ { 3 } + 2 \mathrm { HCl } + \mathrm { SO } _ { 2 } \mathrm { Cl } _ { 2 } {/tex}

{tex} 2 \mathrm { HI } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \longrightarrow \mathrm { I } _ { 2 } + \mathrm { SO } _ { 2 } + 2 \mathrm { H } _ { 2 } \mathrm { O } {/tex}

D

{tex} \mathrm { Ca } ( \mathrm { OH } ) _ { 2 } + \mathrm { H } _ { 2 } \mathrm { SO } _ { 4 } \longrightarrow \mathrm { CaSO } _ { 4 } + 2 \mathrm { H } _ { 2 } \mathrm { O } {/tex}

Explanation



Q 23.    

Correct4

Incorrect-1

The molar conductivities {tex} \Lambda _ { \mathrm { NaOAc } } ^ { \circ } {/tex} and {tex} \Lambda _ { \mathrm { HCl } } ^ { \circ } {/tex} at infinite dilution in water at {tex} 25 ^ { \circ } \mathrm { C } {/tex} are 91.0 and 426.2{tex} \mathrm { S } \mathrm { cm } ^ { 2 } / \mathrm { mol } {/tex}
respectively. To calculate {tex} \Lambda _ { \text {HOAc } } ^ { 6 } , {/tex} the additional value requiredis

A

{tex} \Lambda _ { \mathrm { NaOH } } ^ { \circ } {/tex}

{tex} \Lambda _ { \mathrm { NaCl } } ^ { \circ } {/tex}

C

{tex} \Lambda _ { \mathrm { H } _ { 2 } \mathrm { O } } ^ { \mathrm { o } } {/tex}

D

{tex} \Lambda _ { \mathrm { KCl } } ^ { \circ } {/tex}

Explanation

Q 24.    

Correct4

Incorrect-1

Resistance of a conductivity cell filled with a solution of an electrolyte of concentration {tex}0.1\, \mathrm { M } {/tex} is {tex}100\, \Omega {/tex} . The conductivity of this solution is {tex} 1.29 \mathrm { S } \mathrm { m } ^ { - 1 } . {/tex} Resistance of the same cell when filled with {tex} 0.2\mathrm { M } {/tex} of the same solution is {tex} 520\Omega {/tex} . The molar conductivity of {tex} 0.2\mathrm { M } {/tex} solution of electrolyte will be

A

{tex} 1.24 \times 10 ^ { - 4 } \mathrm { S } \mathrm { m } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

{tex} 12.4 \times 10 ^ { - 4 } \mathrm { S } \mathrm { m } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

C

{tex} 124 \times 10 ^ { - 4 } \mathrm { Sm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

D

{tex} 1240 \times 10 ^ { - 4 } \mathrm { S } \mathrm { m } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

Explanation



Q 25.    

Correct4

Incorrect-1

The equivalent conductances of two strong electrolytes at infinite dilution in {tex} \mathrm { H } _ { 2 } \mathrm { O } {/tex} (where ions move freely through a solution) at {tex} 25 ^ { \circ } \mathrm { C } {/tex} are given below:
{tex} \Lambda _ { \mathrm { CH } _ { 3 } \mathrm { COONa } } ^ { \circ } = 91.0 \mathrm { S } \mathrm { cm } ^ { 2 } / \mathrm { equiv } {/tex}
{tex} \Lambda _ { \mathrm { HCl } } ^ { \circ } = 426.2 \mathrm { S } \mathrm { cm } ^ { 2 } / \mathrm { equiv } {/tex}
What additional information/ quantity one needs to calculate {tex} \Lambda ^ { \circ } {/tex} of an aqueous solution of acetic acid?

A

{tex} \Lambda ^ { \circ } {/tex} of chloroacetic acid {tex} \left( \mathrm { ClCH } _ { 2 } \mathrm { COOH } \right) {/tex}

{tex} \Lambda ^ { \circ } {/tex} of {tex} \mathrm { NaCl } {/tex}

C

{tex} \Lambda ^ { \circ } {/tex} of {tex} \mathrm { CH } _ { 3 } \mathrm { COOK } {/tex}

D

the limiting equivalent coductance of {tex} \mathrm { H } ^ { + } \left( \lambda _ { \mathrm { H } ^ { + } } ^ { \circ } \right) {/tex}

Explanation