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

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Q 1. Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because

A

zinc is lighter than iron

B

zinc has lower melting point than iron

C

zinc has lower negative electrode potential than iron

zinc has higher negative electrode potential than iron.

Explanation


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Q 2. The weight of silver (at. wt. = {tex}108{/tex}) displaced by a quantity of electricity which displaces {tex}5600\ \mathrm { mL } {/tex} of {tex} \mathrm { O } _ { 2 } {/tex} at STP will be

A

5.4 g

B

10.8 g

C

54.0 g

108.0 g

Explanation


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Q 3. At {tex}\mathrm {25^\circ\,C}{/tex} molar conductance of {tex} \mathrm{0.1}{/tex} molar aqueous solution of ammonium hydroxide is {tex}\mathrm {9.54 \ ohm^{-1} cm^2\ mol^{-1}}{/tex} and at infinite dilution its molar conductance is {tex}\mathrm {238\ ohm^{-1}\ cm^2\ mol^{-1}}{/tex}. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

4.008{tex} \% {/tex}

B

40.800{tex} \% {/tex}

C

2.080{tex} \% {/tex}

D

20.800{tex} \% {/tex}

Explanation


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Q 4. A button cell used in watches function as following:
{tex} \mathrm { Zn } _ { ( s ) } + \mathrm { Ag } _ { 2 } \mathrm { O } _ { ( s ) } + \mathrm { H } _ { 2 } \mathrm { O } _ { ( l ) } \rightleftharpoons 2 \mathrm { Ag } _ { ( s ) } +\mathrm {Zn^{2+}_{(aq)}} +2 \mathrm { OH } _ { ( a q ) } {/tex}
If half cell potentials are
{tex} \mathrm { Zn } ^ { 2 + }_{( aq)} + 2 e ^ { - } \rightarrow \mathrm { Zn _ { ( s ) } ; E} ^ { \circ } = - 0.76 \mathrm { V } {/tex}
{tex} \mathrm { Ag_2 {O_{(s)}}} +\mathrm {H_2O}_{(l)}+ 2 e ^ { - } \rightarrow \mathrm { 2Ag } _ { ( s ) } + \mathrm {2OH^-_{(aq)}; E} ^ { \circ } = + 0.34 \mathrm { V } {/tex}
The cell potential will be

A

{tex} 0.84\,\mathrm { V } {/tex}

B

{tex} 1.34\,\mathrm { V } {/tex}

{tex} 1.10\,\mathrm { V } {/tex}

D

{tex} 0.42\,\mathrm { V } {/tex}

Explanation

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Q 5. Consider the half-cell reduction reaction
{tex} \mathrm { Mn } ^ { 2 + } + 2 e ^ { - } \rightarrow \mathrm { Mn , E }^ { \circ } = - 1.18 \mathrm { V } {/tex}
{tex} \mathrm { 2Mn } ^ { 2 + } \rightarrow \mathrm { 2Mn ^ { 3 + } + 2e ^ { - } , E} ^ { \circ } = - 1.51 \mathrm { V } {/tex}
The {tex} \mathrm E ^ { \circ } {/tex} for the reaction {tex} 3 \mathrm { Mn } ^ { 2 + } \rightarrow \mathrm { Mn } + 2 \mathrm { Mn } ^ { 3 + }, {/tex} and possibility of the forward reaction are respectively

A

{tex} - 4.18 \mathrm { V } {/tex} and yes

B

{tex} + 0.33 \mathrm { V } {/tex} and yes

C

{tex} + 2.69 \mathrm { V } {/tex} and no

{tex} - 2.69 \mathrm { V } {/tex} and no

Explanation


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Q 6. Molar conductivities {tex}(\wedge_m^\circ){/tex} at infinite dilution of {tex}\mathrm {NaCl, HCl}{/tex} and {tex}\mathrm {CH_3COONa}{/tex} are {tex} \mathrm 126.4,425.9{/tex} and {tex} \mathrm 91.0{/tex} {tex}\mathrm {S\ cm^2\ mol^{-1}}{/tex} respectively. {tex}(\wedge^\circ_m){/tex} for {tex}\mathrm {CH_3COOH}{/tex} will be.

A

{tex}425.5\, \mathrm { S } \,\mathrm{ cm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

B

{tex}180.5\, \mathrm { S\,cm } ^ { 2 } \mathrm { mol } ^ { -1 } {/tex}

C

{tex}290.8 \,\mathrm { S } \,\mathrm { cm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

{tex}390.5\, \mathrm { S\,cm } ^ { 2 } \mathrm { mol } ^ { - 1 } {/tex}

Explanation


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Q 7. The Gibb's energy for the decomposition of {tex} \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } {/tex} at {tex} 500 ^ { \circ } \mathrm { C } {/tex} is as follows
{tex} \frac { 2 } { 3 } \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } \rightarrow \frac { 4 } { 3 } \mathrm { Al } + \mathrm { O } _ { 2 } {/tex}
{tex} \mathrm { \Delta _ { r } G} = + 960\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}
The potential difference needed for the electrolytic reduction of aluminium oxide {tex} \left( \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } \right) {/tex} at {tex} 500 ^ { \circ } \mathrm { C } {/tex} is at least

A

{tex} 4.5\,\mathrm { V } {/tex}

B

{tex}3.0 \,\mathrm { V } {/tex}

{tex}2.5\, \mathrm { V } {/tex}

D

{tex} 5.0\,\mathrm { V } {/tex}

Explanation


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Q 8. The electrode potential for {tex}\mathrm{Cu^{2+}_{(aq)}+e^-\rightarrow Cu^+_{(aq)}}{/tex} and {tex} \mathrm { Cu^{+}_{(aq)}+e^-\rightarrow Cu}_{(s)}{/tex} are + {tex} \mathrm{ 0.15 V}{/tex} and + {tex} \mathrm { 0.50 V}{/tex} respectively. The value of {tex} \mathrm{ E^\circ_{cu^{2+}/Cu}}{/tex} will be

A

{tex} 0.500\,\mathrm { V } {/tex}

{tex} 0.325\,\mathrm { V } {/tex}

C

{tex} 0.650\,\mathrm { V } {/tex}

D

{tex} 0.150\,\mathrm { V } {/tex}

Explanation


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Q 9. Standard electrode potential for {tex} \mathrm { Sn } ^ { 4 + } / \mathrm { Sn } ^ { 2 + } {/tex} couple is {tex} + 0.15 \mathrm { V } {/tex} and that for the {tex} \mathrm { Cr } ^ { 3 + } / \mathrm { Cr } {/tex} couple is {tex} - 0.74 \mathrm { V } {/tex} . These two couples in their standard state are connected to make a cell. The cell potential will be

A

{tex} + 1.19 \,\mathrm { V } {/tex}

{tex} + 0.89\, \mathrm { V } {/tex}

C

{tex} + 0.18 \,\mathrm { V } {/tex}

D

{tex} + 1.83 \,\mathrm { V } {/tex}

Explanation

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Q 10. Given :
(i) {tex} \mathrm { Cu } ^ { 2 + } + 2 e ^ { - } \rightarrow \mathrm { Cu , E }^ { \circ } = 0.337 \mathrm { V } {/tex}
(ii) {tex} \mathrm { Cu } ^ { 2 + } + e ^ { - } \rightarrow \mathrm { Cu ^ { + } , E }^ { \circ } = 0.153 \mathrm { V } {/tex}
Electrode potential, {tex} \mathrm E ^ { \circ } {/tex} for the reaction,
{tex} \quad \mathrm { Cu } ^ { + } + e ^ { - } \rightarrow \mathrm { Cu } , {/tex} will be

A

{tex} 0.90\,\mathrm { V } {/tex}

B

{tex}0.30\, \mathrm { V } {/tex}

C

{tex}0.38\, \mathrm { V } {/tex}

{tex} 0.52\,\mathrm { V } {/tex}

Explanation



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Q 11. {tex} \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } {/tex} is reduced by electrolysis at low potentials and high currents. If {tex} 4.0 \times 10 ^ { 4 } {/tex} amperes of current is passed through molten {tex} \mathrm { Al } _ { 2 } \mathrm { O } _ { 3 } {/tex} for {tex} \mathrm 6{/tex} hours, what mass of aluminium is produced? (Assume {tex} \mathrm 100 \% {/tex} current efficiency,{tex} \left(\text { at. mass of } \mathrm { Al } = 27\ \mathrm { g } \ \mathrm { mol } ^ { - 1 } \right) {/tex}

{tex} 8.1 \times 10 ^ { 4 } {/tex} g

B

{tex} 2.4 \times 10 ^ { 5 } {/tex}g

C

{tex} 1.3 \times 10 ^ { 4 } {/tex} g

D

{tex} 9.0 \times 10 ^ { 3 } {/tex} g

Explanation


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Q 12. The equivalent conductance of {tex} \mathrm M / 32 {/tex} solution of a weak monobasic acid is {tex} 8.0\ \mathrm { mho }\ \mathrm { cm } ^ { 2 } {/tex} and at infinite dilution is {tex} 400\ \mathrm { mho } \ \mathrm { cm } ^ { 2 } . {/tex} The dissociation constant of this acid is

A

{tex} 1.25 \times 10 ^ { - 6 } {/tex}

B

{tex} 6.25 \times 10 ^ { - 4 } {/tex}

C

{tex} 1.25 \times 10 ^ { - 4 } {/tex}

{tex} 1.25 \times 10 ^ { - 5 } {/tex}

Explanation



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Q 13. On the basis of the following {tex} \mathrm E ^ { \circ } {/tex} values, the strongest oxidizing agent is {tex} \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } \right] ^ { 4-} \rightarrow \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } \right] ^ { 3 - } + e ^ { - 1 } ; \mathrm E ^ { \circ } = - 0.35 \mathrm { V } {/tex}
{tex} \mathrm { Fe } ^ { 2 + } \rightarrow \mathrm { Fe } ^ { 3 + } + e ^ { - 1 } ; \quad\mathrm E ^ { \circ } = - 0.77 \mathrm { V } {/tex}

{tex} \mathrm { Fe } ^ { 3+ } {/tex}

B

{tex} \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } \right] ^ { 3- } {/tex}

C

{tex} \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } \right] ^ { 4- } {/tex}

D

{tex} \mathrm { Fe } ^ { 2+ } {/tex}

Explanation


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Q 14. A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as

A

dynamo

B

Ni-Cd cell

fuel cell

D

electrolytic cell.

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Q 15. When 0.1 mol {tex} \mathrm { MnO } _ { 4 } ^ { 2 - } {/tex} is oxidised the quantity of electricity required to completely oxidise {tex} \mathrm { MnO } _ { 4 } ^ { 2 - } {/tex} to {tex} \mathrm { MnO } _ { 4 } ^ { - } {/tex} is

A

{tex} \mathrm { 96500 \ C } {/tex}

B

{tex} \mathrm{ 2 \times 96500\ C } {/tex}

{tex} \mathrm { 9650\ C } {/tex}

D

{tex} \mathrm { 96.50\ C } {/tex}

Explanation


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Q 16. How many gram of cobalt metal will be deposited when a solution of cobalt (II) chloride is electrolyzed with a current of {tex} \mathrm 10 {/tex} amperes for {tex}109{/tex} minutes {tex} ( 1 \text { Faraday } = 96,500 \mathrm { C } ; \text { Atomic } {/tex} {tex} \text { mass of } \mathrm { Co } = 59 \mathrm { u } ) {/tex}

A

4.0

20.0

C

40.0

D

0.66

Explanation

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Q 17. Standard electrode potential of three metals {tex} X , Y {/tex} and {tex} Z {/tex} are {tex} - 1.2\ \mathrm { V } , + 0.5\ \mathrm { V } {/tex} and {tex} - 3.0\ \mathrm { V } {/tex} respectively. The reducing power of these metals will be

A

{tex} Y > Z > X {/tex}

B

{tex} Y > X > Z {/tex}

{tex} Z > X > Y {/tex}

D

{tex} Y > Y > Z {/tex}

Explanation


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Q 18. A solution contains {tex} \mathrm { Fe } ^ { 2 + } , \mathrm { Fe } ^ { 3 + } {/tex} and {tex}\mathrm {I^-}{/tex} ions. This solution was treated with iodine at {tex} 35 ^ { \circ } \mathrm { C . E} ^ { \circ } {/tex} for {tex} \mathrm { Fe } ^ { 3 + } / \mathrm { Fe } ^ { 2 + } \mathrm { is } + 0.77\ \mathrm { V } {/tex} and {tex} \mathrm E ^ { \circ } {/tex} for {tex} \mathrm{{ I } _ { 2 } / 2 I^-} = 0.536\ \mathrm { V } {/tex} . The favourable redox reaction is

A

{tex} \mathrm { I } _ { 2 } {/tex} will be reduced to {tex} \mathrm { I^- } {/tex}

B

there will be no redox reaction

{tex} \mathrm { I } ^ { - } {/tex} will be oxidised to {tex} \mathrm { I } _ { 2 } {/tex}

D

{tex} \mathrm { Fe } ^ { 2 + } {/tex} will be oxidised to {tex} \mathrm { Fe } ^ { 3 + } {/tex}

Explanation


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Q 19. Standard free energies of formation (in kJ/mol) at {tex} \mathrm{298 K}{/tex} are {tex} \mathrm{-237.2,-394.4}{/tex} and {tex} \mathrm{-8.2}{/tex} for {tex}\mathrm{H_2O_{(\ell)},CO_{2(g)}}{/tex} {tex}\mathrm {pentane_ {(g)}}{/tex} respectively. The value of {tex} \mathrm E^{\circ}_{cell}{/tex} for the pentane-oxygen fuel cell is

{tex} 1.0968\,\mathrm { V } {/tex}

B

{tex} 0.0968\,\mathrm { V } {/tex}

C

{tex}1.968\, \mathrm { V } {/tex}

D

{tex}2.0968\, \mathrm { V } {/tex}

Explanation


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Q 20. The equilibrium constant of the reaction:
{tex}\mathrm {Cu_{(s)}+2Ag^+_{(aq)}\rightarrow Cu^{2+}_{(aq)}+2Ag_{(s)}}{/tex},{tex}\ E^{\circ}=0.46 \ V{/tex} at 298 K is

A

{tex} 2.0 \times 10 ^ { 10 } {/tex}

B

{tex} 4.0 \times 10 ^ { 10 } {/tex}

{tex} 4.0 \times 10 ^ { 15 } {/tex}

D

{tex} 2.4 \times 10 ^ { 10 } {/tex}

Explanation



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Q 21. The mass of carbon anode consumed (giving only carbon dioxide) in the production of {tex} 270\ \mathrm { kg } {/tex} of aluminium metal from bauxite by the Hall process is
(Atomic mass : Al = 27)

A

{tex}270\ \mathrm { kg } {/tex}

B

{tex} 540\ \mathrm { kg } {/tex}

{tex} 90\ \mathrm { kg } {/tex}

D

{tex}180\ \mathrm { kg } {/tex}

Explanation



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Q 22. The e.m.f of a Daniell cell at 298 K is {tex}E_1{/tex}
{tex} \mathrm { Zn } \left| \underset { ( 0.01 \mathrm { M } ) } { \mathrm { ZnSO } _ { 4 } } \| \begin{array} { l } { \mathrm { CuSO } _ { 4 } } \\ { ( 1.0 \mathrm { M } ) } \end{array} \right| ^ { \mathrm { Cu } } {/tex}
When the concentration of {tex}\mathrm{ZnSO_4}{/tex} is 1.0 M and that of {tex}\mathrm{ CuSO_4}{/tex} is 0.01 M, the e.m.f changed to {tex}E_2{/tex}. What is the relationship between {tex}E_1{/tex} and {tex}E_2{/tex}?

{tex} E _ { 1 } > E _ { 2 } {/tex}

B

{tex} E _ { 1 } < E _ { 2 } {/tex}

C

{tex} E _ { 1 } = E _ { 2 } {/tex}

D

{tex} E _ { 2 } = 0 \neq E _ { 1 } {/tex}

Explanation


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Q 23. Standard electrode potentials are
{tex} \mathrm { Fe } ^ { 2 + } / \mathrm { Fe }\ ; {/tex} {tex} E ^ { \circ } = - 0.44 {/tex} and
{tex} \mathrm { Fe } ^ { 3 + }/\mathrm { Fe } ^ { 2 + } ; E ^ { \circ } = 0.77 {/tex}
{tex}\mathrm { Fe } ^ { 2 + } , \mathrm { Fe } ^ { 3 } {/tex} and {tex} \mathrm { Fe } {/tex} blocks are kept together, then

A

{tex} \mathrm { Fe } ^ { 3 + } {/tex} increases

{tex} \mathrm { Fe } ^ { 3 + } {/tex} decreases

C

{tex} \mathrm { Fe } ^ { 2 + } / \mathrm { Fe } ^ { 3 + } {/tex} remains unchanged

D

{tex} \mathrm { Fe } ^ { 2 + } {/tex} decreases.

Explanation


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Q 24. Equivalent conductances of {tex} \mathrm { Ba } ^ { 2 + } {/tex} and {tex} \mathrm { Cl } ^ { - } {/tex} ions are 127 and {tex}76\, \mathrm { ohm } ^ { - 1 } \mathrm { cm } ^ { - 1 } \mathrm { eq } ^ { - 1 } {/tex} respectively. Equivalent conductance of {tex} \mathrm { BaCl } _ { 2 } {/tex} at infinite dilution is

139.5

B

101.5

C

203

D

279

Explanation



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Q 25. Reduction potential for the following half-cell reactions are
{tex} \mathrm { Zn } = \mathrm { Zn } ^ { 2 + } + 2 e ^ { - } ; E ^ { \circ } = + 0.76\ \mathrm { V }; {/tex}
{tex} \mathrm { Fe } = \mathrm { Fe } ^ { 2 + } + 2 e ^ { - } ; E ^ { \circ } = + 0.44\ \mathrm { V }. {/tex}
The EMF for the cell reaction
{tex} \mathrm { Fe } ^ { 2 + } + \mathrm { Zn } \rightarrow \mathrm { Zn } ^ { 2 + } + \mathrm { Fe } {/tex} will be

A

{tex} - 0.32 \ \mathrm { V } {/tex}

B

{tex} + 1.20 \ \mathrm { V } {/tex}

C

{tex} - 1.20 \ \mathrm { V } {/tex}

{tex} + 0.32 \ \mathrm { V } {/tex}

Explanation