A English

Nernst equation and ECS Questions in English

Class 12 Chemistry · Electrochemistry · Nernst equation and ECS

365+

Questions

English

Language

100%

With Solutions

Showing 49 of 365 questions in English

1
EasyMCQ
The relationship between standard reduction potential of a cell and the equilibrium constant is shown by:
A
$E_{cell}^0 = \frac{n}{0.059} \log K_c$
B
$E_{cell}^0 = \frac{0.059}{n} \log K_c$
C
$E_{cell}^0 = 0.059 \, n \, \log K_c$
D
$E_{cell}^0 = \frac{\log K_c}{n}$

Solution

(B) At equilibrium,the cell potential $E_{cell} = 0$.
According to the Nernst equation: $E_{cell} = E_{cell}^0 - \frac{2.303 \, RT}{nF} \log K_c$.
Setting $E_{cell} = 0$,we get $E_{cell}^0 = \frac{2.303 \, RT}{nF} \log K_c$.
At $298 \ K$,the value of $\frac{2.303 \, RT}{F}$ is approximately $0.0591 \, V$.
Therefore,$E_{cell}^0 = \frac{0.0591}{n} \log K_c$.
2
DifficultMCQ
If the $Zn^{2+}/Zn$ electrode is diluted to $100$ times,what is the change in the electrode potential?
A
Increase of $59 \ mV$
B
Decrease of $59 \ mV$
C
Increase of $29.5 \ mV$
D
Decrease of $29.5 \ mV$

Solution

(B) The electrode potential for $Zn^{2+}/Zn$ is given by the Nernst equation: $E = E^0 - \frac{0.0591}{n} \log \frac{1}{[Zn^{2+}]}$.
When the concentration is diluted $100$ times,the new concentration becomes $[Zn^{2+}]' = \frac{[Zn^{2+}]}{100}$.
The change in potential is $\Delta E = E' - E = - \frac{0.0591}{2} \log \frac{1}{[Zn^{2+}]/100} - (- \frac{0.0591}{2} \log \frac{1}{[Zn^{2+}]})$.
$\Delta E = - \frac{0.0591}{2} (\log \frac{100}{[Zn^{2+}]} - \log \frac{1}{[Zn^{2+}]}) = - \frac{0.0591}{2} \log(100) = - \frac{0.0591}{2} \times 2 = -0.0591 \ V$.
Thus,the electrode potential decreases by $59 \ mV$.
3
MediumMCQ
If a hydrogen electrode is dipped in two solutions of $pH = 3$ and $pH = 6$ and a salt bridge is connected,the e.m.f. of the resulting cell is ............ $V$.
A
$0.177$
B
$0.3$
C
$0.052$
D
$0.104$

Solution

(A) The cell reaction for a concentration cell with hydrogen electrodes is: $H^+ (pH=3) \rightarrow H^+ (pH=6)$.
Using the Nernst equation at $298 \ K$: $E_{cell} = E^0_{cell} - \frac{0.0591}{n} \log \frac{[H^+]_{cathode}}{[H^+]_{anode}}$.
Since $E^0_{cell} = 0$ for a concentration cell and $n = 1$,we have:
$E_{cell} = -0.0591 \log \frac{10^{-6}}{10^{-3}}$.
$E_{cell} = -0.0591 \log (10^{-3}) = -0.0591 \times (-3) = 0.177 \ V$.
4
MediumMCQ
The hydrogen electrode is dipped in a solution of $pH = 3$ at $25\,^oC$. The potential of the cell would be ............. $V$ (the value of $2.303\,RT/F$ is $0.059\,V$).
A
$0.177$
B
$-0.177$
C
$0.087$
D
$0.059$

Solution

(B) The reduction potential of the hydrogen electrode is given by the Nernst equation:
$E_{H^+/H_2} = E^o_{H^+/H_2} - \frac{0.059}{n} \log \frac{1}{[H^+]}$
Since $E^o_{H^+/H_2} = 0 \, V$ and $n = 1$,the equation simplifies to:
$E = -0.059 \times pH$
Given $pH = 3$:
$E = -0.059 \times 3 = -0.177 \, V$.
5
EasyMCQ
The name of the equation showing the relation between electrode potential $(E)$,standard electrode potential $(E^o)$,and concentration of ions in solution is
A
Kohlrausch's equation
B
Nernst's equation
C
Ohm's equation
D
Faraday's equation

Solution

(B) The equation that relates the electrode potential $(E)$,the standard electrode potential $(E^o)$,and the concentration of ions in the solution is known as the Nernst equation.
For a general reaction $M^{n+} + ne^- \rightarrow M(s)$,the Nernst equation is given by $E = E^o - (RT/nF) \ln([M]/[M^{n+}])$.
Thus,the correct option is $(B)$.
6
EasyMCQ
The correct representation of Nernst's equation for the reduction of a metal ion $M^{n+}$ to metal $M$ is:
A
$E_{M^{n+}/M} = E^o_{M^{n+}/M} + \frac{0.0591}{n}\log ([M^{n+}])$
B
$E_{M^{n+}/M} = E^o_{M^{n+}/M} - \frac{0.0591}{n}\log ([M^{n+}])$
C
$E_{M^{n+}/M} = E^o_{M^{n+}/M} + \frac{n}{0.0591}\log ([M^{n+}])$
D
None of the above

Solution

(A) The Nernst equation for the electrode reaction $M^{n+} + ne^- \rightarrow M(s)$ is given by:
$E_{M^{n+}/M} = E^o_{M^{n+}/M} - \frac{RT}{nF} \ln \frac{1}{[M^{n+}]}$
Using $\ln x = 2.303 \log x$,we get:
$E_{M^{n+}/M} = E^o_{M^{n+}/M} - \frac{2.303RT}{nF} \log \frac{1}{[M^{n+}]}$
$E_{M^{n+}/M} = E^o_{M^{n+}/M} + \frac{2.303RT}{nF} \log [M^{n+}]$
At $298 \ K$,the value of $\frac{2.303RT}{F} \approx 0.0591 \ V$.
Therefore,$E_{M^{n+}/M} = E^o_{M^{n+}/M} + \frac{0.0591}{n} \log [M^{n+}]$.
Thus,option $A$ is correct.
7
EasyMCQ
$E^0 = \frac{RT}{nF} \ln K_{eq}$. This is called
A
Gibbs equation
B
Gibbs-Helmholtz equation
C
Nernst equation
D
Van der Waal's equation

Solution

(C) The given expression $E^0 = \frac{RT}{nF} \ln K_{eq}$ is derived from the Nernst equation.
At equilibrium,the cell potential $E = 0$ and the reaction quotient $Q = K_{eq}$.
Substituting these into the Nernst equation $E = E^0 - \frac{RT}{nF} \ln Q$,we get $0 = E^0 - \frac{RT}{nF} \ln K_{eq}$,which simplifies to $E^0 = \frac{RT}{nF} \ln K_{eq}$.
8
EasyMCQ
Which of the following is the correct expression for the electrode potential of a cell?
A
$E = E^o - \frac{RT}{nF} \ln \frac{[\text{product}]}{[\text{reactant}]}$
B
$E = E^o + \frac{RT}{F} \ln \frac{[\text{product}]}{[\text{reactant}]}$
C
$E = E^o - \frac{RT}{nF} \ln \frac{[\text{reactant}]}{[\text{product}]}$
D
$E = - \frac{RT}{F} \ln \frac{[\text{product}]}{[\text{reactant}]}$

Solution

(A) The Nernst equation describes the relationship between the cell potential and the reaction quotient for an electrochemical cell.
The general form of the Nernst equation is given by $E = E^o - \frac{RT}{nF} \ln Q$,where $Q$ is the reaction quotient,defined as the ratio of the concentration of products to the concentration of reactants.
Therefore,the correct expression is $E = E^o - \frac{RT}{nF} \ln \frac{[\text{product}]}{[\text{reactant}]}$.
9
EasyMCQ
The Nernst equation is related to:
A
The electrode potential and concentration of ions in the solution
B
Equilibrium constant and concentration of ions
C
Free energy change and $E$.$M$.$F$. of the cell
D
None of these

Solution

(A) The Nernst equation relates the cell potential $(E_{cell})$ to the standard cell potential $(E^o_{cell})$,the reaction quotient $(Q)$,and the concentration of ions in the solution.
It is given by the formula: $E_{cell} = E^o_{cell} - \frac{2.303RT}{nF} \log Q$.
Since the cell potential depends on the concentration of ions,option $A$ is the most appropriate description of its primary application.
10
MediumMCQ
The $E^o$ for the cell $Zn|Zn^{2+}_{(aq)}||Cu^{2+}_{(aq)}|Cu$ is $1.10 \ V$ at $25 \ ^oC$. The equilibrium constant for the reaction $Zn + Cu^{2+}_{(aq)} \rightleftharpoons Cu + Zn^{2+}_{(aq)}$ is of the order of:
A
$10^{-28}$
B
$10^{+37}$
C
$10^{+18}$
D
$10^{+17}$

Solution

(B) For the given cell reaction,the number of electrons transferred is $n = 2$.
Using the Nernst equation at equilibrium: $E_{cell}^o = \frac{0.0591}{n} \log K_c$.
Substituting the values: $1.10 = \frac{0.0591}{2} \log K_c$.
$\log K_c = \frac{1.10 \times 2}{0.0591} \approx 37.22$.
Therefore,$K_c = 10^{37.22} \approx 10^{37}$.
11
MediumMCQ
For the cell reaction $Cu^{2+}_{(C_1, aq)} + Zn_{(s)} \rightarrow Zn^{2+}_{(C_2, aq)} + Cu_{(s)}$ of an electrochemical cell,the change in free energy at a given temperature is a function of
A
ln $(C_1)$
B
ln $(C_2)$
C
ln $(C_1 + C_2)$
D
ln $(C_2 / C_1)$

Solution

(D) The Nernst equation for the given cell reaction is $E_{cell} = E^o_{cell} - \frac{RT}{nF} \ln \frac{[Zn^{2+}]}{[Cu^{2+}]} = E^o_{cell} - \frac{RT}{nF} \ln \frac{C_2}{C_1}$.
The relationship between Gibbs free energy change and cell potential is given by $\Delta G = -nF E_{cell}$.
Substituting the expression for $E_{cell}$,we get $\Delta G = -nF \left( E^o_{cell} - \frac{RT}{nF} \ln \frac{C_2}{C_1} \right) = -nF E^o_{cell} + RT \ln \frac{C_2}{C_1}$.
Thus,the change in free energy $\Delta G$ is a function of $\ln \left( \frac{C_2}{C_1} \right)$.
12
DifficultMCQ
The e.m.f. of the cell in which the following reaction $Zn_{(s)} + Ni^{2+}(a = 1.0) \rightleftharpoons Zn^{2+}(a = 10) + Ni_{(s)}$ occurs,is found to be $0.5105 \ V$ at $298 \ K$. The standard e.m.f. of the cell is ............ $V$.
A
$0.4810$
B
$0.54$
C
$0.5696$
D
$-0.5105$

Solution

(B) The cell reaction is: $Zn_{(s)} + Ni^{2+}(a = 1.0) \rightarrow Zn^{2+}(a = 10) + Ni_{(s)}$.
Here,$Zn$ undergoes oxidation $(Zn \rightarrow Zn^{2+} + 2e^-)$,acting as the anode,and $Ni^{2+}$ undergoes reduction $(Ni^{2+} + 2e^- \rightarrow Ni)$,acting as the cathode.
Using the Nernst equation at $298 \ K$:
$E_{cell} = E_{cell}^{o} - \frac{0.0591}{n} \log \frac{[Zn^{2+}]}{[Ni^{2+}]}$
Given:
$E_{cell} = 0.5105 \ V$
$n = 2$
$[Zn^{2+}] = 10$
$[Ni^{2+}] = 1.0$
Substituting the values:
$0.5105 = E_{cell}^{o} - \frac{0.0591}{2} \log \frac{10}{1}$
$0.5105 = E_{cell}^{o} - 0.02955 \times 1$
$E_{cell}^{o} = 0.5105 + 0.02955 = 0.54005 \ V \approx 0.54 \ V$.
Thus,the standard e.m.f. of the cell is $0.54 \ V$.
13
MediumMCQ
For the redox reaction $Zn_{(s)} + Cu^{2+}(0.1 \ M) \to Zn^{2+}(1 \ M) + Cu_{(s)}$ taking place in a cell,$E_{cell}^o$ is $1.10 \ V$. $E_{cell}$ for the cell will be ............ $V$ $\left( 2.303 \frac{RT}{F} = 0.0591 \right)$
A
$2.14$
B
$1.80$
C
$1.07$
D
$0.82$

Solution

(C) The Nernst equation for the cell reaction is given by:
$E_{cell} = E_{cell}^o - \frac{0.0591}{n} \log \frac{[Zn^{2+}]}{[Cu^{2+}]}$
Here,$n = 2$ (number of electrons transferred).
Substituting the given values:
$E_{cell} = 1.10 - \frac{0.0591}{2} \log \frac{1}{0.1}$
$E_{cell} = 1.10 - 0.02955 \times \log(10)$
Since $\log(10) = 1$,we get:
$E_{cell} = 1.10 - 0.02955 = 1.07045 \ V \approx 1.07 \ V$.
14
DifficultMCQ
The $emf$ of a $Daniel$ cell at $298 \ K$ is ${E_1}$ for the cell reaction $Zn|ZnSO_4(0.01 \ M)||CuSO_4(1.0 \ M)|Cu$. When the concentration of $ZnSO_4$ is $1.0 \ M$ and that of $CuSO_4$ is $0.01 \ M$,the $emf$ changes to ${E_2}$. What is the relationship between ${E_1}$ and ${E_2}$?
A
${E_2} = 0 \neq {E_1}$
B
${E_1} > {E_2}$
C
${E_1} < {E_2}$
D
${E_1} = {E_2}$

Solution

(B) The cell reaction is $Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)$.
Using the $Nernst$ equation: $E = E^o - \frac{0.0591}{2} \log \frac{[Zn^{2+}]}{[Cu^{2+}]}$.
For ${E_1}$: $[Zn^{2+}] = 0.01 \ M$ and $[Cu^{2+}] = 1.0 \ M$,so ${E_1} = E^o - \frac{0.0591}{2} \log \frac{0.01}{1} = E^o + 0.0591$.
For ${E_2}$: $[Zn^{2+}] = 1.0 \ M$ and $[Cu^{2+}] = 0.01 \ M$,so ${E_2} = E^o - \frac{0.0591}{2} \log \frac{1}{0.01} = E^o - 0.0591$.
Therefore,${E_1} > {E_2}$.
15
DifficultMCQ
For a cell reaction involving a two-electron change,the standard emf of the cell is found to be $0.295 \ V$ at $25 \ ^oC$. The equilibrium constant of the reaction at $25 \ ^oC$ will be
A
$1 \times 10^{-10}$
B
$29.5 \times 10^{-2}$
C
$10$
D
$1 \times 10^{10}$

Solution

(D) The relationship between standard emf $(E^o)$ and equilibrium constant $(K)$ is given by the equation: $\log \ K = \frac{nFE^o}{2.303 \ RT}$.
Given: $n = 2$,$E^o = 0.295 \ V$,$T = 298 \ K$,$F = 96500 \ C \ mol^{-1}$,$R = 8.314 \ J \ K^{-1} \ mol^{-1}$.
Substituting the values: $\log \ K = \frac{2 \times 96500 \times 0.295}{2.303 \times 8.314 \times 298}$.
$\log \ K = \frac{56935}{5705.8} \approx 9.978$.
Since $\log \ K \approx 10$,we get $K = 10^{10}$.
16
EasyMCQ
Which of the following conditions will increase the voltage of the cell,represented by the equation $Cu_{(s)} + 2Ag^{+}_{(aq)} \to Cu^{2+}_{(aq)} + 2Ag_{(s)}$?
A
Increase in the concentration of $Ag^{+}$ ions
B
Increase in the concentration of $Cu^{2+}$ ions
C
Increase in the dimension of the silver electrode
D
Increase in the dimension of the copper electrode

Solution

(A) The cell reaction is $Cu_{(s)} + 2Ag^{+}_{(aq)} \to Cu^{2+}_{(aq)} + 2Ag_{(s)}$.
According to the Nernst equation,the cell potential is given by $E_{cell} = E^{\circ}_{cell} - \frac{0.0591}{2} \log \frac{[Cu^{2+}]}{[Ag^{+}]^2}$.
To increase the $E_{cell}$,the value of the logarithmic term $\frac{[Cu^{2+}]}{[Ag^{+}]^2}$ must decrease.
This can be achieved by increasing the concentration of the reactant $[Ag^{+}]$ or decreasing the concentration of the product $[Cu^{2+}]$.
Therefore,an increase in the concentration of $Ag^{+}$ ions will increase the voltage of the cell.
17
MediumMCQ
Which will increase the voltage of the cell $Sn_{(s)} + 2Ag^{+}_{(aq)} \to Sn^{2+}_{(aq)} + 2Ag_{(s)}$?
A
Increase in the concentration of $Ag^{+}$ ions
B
Increase in the concentration of $Sn^{2+}$ ions
C
Increase in size of the silver rod
D
None of these

Solution

(A) The cell reaction is $Sn_{(s)} + 2Ag^{+}_{(aq)} \to Sn^{2+}_{(aq)} + 2Ag_{(s)}$.
According to the Nernst equation: $E_{cell} = E^{o}_{cell} - \frac{0.0591}{2} \log \frac{[Sn^{2+}]}{[Ag^{+}]^2}$.
This can be rewritten as: $E_{cell} = E^{o}_{cell} + \frac{0.0591}{2} \log \frac{[Ag^{+}]^2}{[Sn^{2+}]}$.
To increase the voltage $(E_{cell})$,the value of the logarithmic term must increase.
This occurs if the concentration of the reactant $[Ag^{+}]$ increases or the concentration of the product $[Sn^{2+}]$ decreases.
Therefore,an increase in the concentration of $Ag^{+}$ ions will increase the voltage of the cell.
18
DifficultMCQ
What will be the $emf$ for the given cell $Pt|H_2(P_1)|H^{+}_{(aq)}||H_2(P_2)|Pt$?
A
$\frac{RT}{F}\log \frac{P_1}{P_2}$
B
$\frac{RT}{2F}\log \frac{P_1}{P_2}$
C
$\frac{RT}{F}\log \frac{P_2}{P_1}$
D
None of these

Solution

(B) Anodic reaction: $H_2(P_1) \to 2H^{+} + 2e^-$
Cathodic reaction: $2H^{+} + 2e^- \to H_2(P_2)$
Overall cell reaction: $H_2(P_1) \to H_2(P_2)$
Using the Nernst equation: $E_{cell} = E^0_{cell} - \frac{RT}{nF} \ln Q$
Here,$n = 2$ and $E^0_{cell} = 0$ for a concentration cell.
$E_{cell} = 0 - \frac{RT}{2F} \ln \frac{P_2}{P_1} = \frac{RT}{2F} \ln \frac{P_1}{P_2}$
Converting natural log to base $10$: $E_{cell} = \frac{2.303 RT}{2F} \log \frac{P_1}{P_2}$
Considering the proportionality,the expression matches option $B$.
19
MediumMCQ
What is the potential of a cell containing two hydrogen electrodes,the negative one in contact with $10^{-8} \ M \ H^{+}$ and the positive one in contact with $0.025 \ M \ H^{+}$? (in $V$)
A
$0.18$
B
$0.28$
C
$0.38$
D
$0.48$

Solution

(C) The cell reaction is a concentration cell: $H^{+} (0.025 \ M) \to H^{+} (10^{-8} \ M)$.
Using the Nernst equation for a concentration cell at $298 \ K$:
$E_{cell} = E^{\circ}_{cell} - \frac{0.0591}{n} \log \frac{[H^{+}]_{cathode}}{[H^{+}]_{anode}}$
Since it is a hydrogen concentration cell,$E^{\circ}_{cell} = 0 \ V$ and $n = 1$.
$E_{cell} = 0 - 0.0591 \log \frac{10^{-8}}{0.025}$
$E_{cell} = -0.0591 \log (4 \times 10^{-7})$
$E_{cell} = -0.0591 (\log 4 + \log 10^{-7})$
$E_{cell} = -0.0591 (0.602 - 7) = -0.0591 (-6.398) \approx 0.378 \ V \approx 0.38 \ V$.
20
EasyMCQ
The standard cell potential $E^o$ for the reaction $aA + bB \to cC + dD$ is related to the equilibrium constant $K_c$ by the expression:
A
$E^o = \frac{RT}{nF} \ln K_c$
B
$E^o = -\frac{RT}{nF} \ln K_c$
C
$E^o = \frac{nF}{RT} \ln K_c$
D
$E^o = -\frac{nF}{RT} \ln K_c$

Solution

(A) The relationship between the standard cell potential $E^o$ and the equilibrium constant $K_c$ is given by the Nernst equation at equilibrium,where $E_{cell} = 0$.
The equation is $\Delta G^o = -nFE^o = -RT \ln K_c$.
Rearranging this gives $E^o = \frac{RT}{nF} \ln K_c$.
21
DifficultMCQ
What is the potential of a half-cell consisting of a zinc electrode in $0.01 \ M$ $ZnSO_4$ solution at $25 \ ^\circ C$ (Given $E^o_{Zn^{2+}/Zn} = -0.763 \ V$) (in $V$)?
A
$0.8221$
B
$8.221$
C
$-0.8221$
D
$-0.7039$

Solution

(C) The half-cell reaction is: $Zn^{2+}(aq) + 2e^- \rightarrow Zn(s)$.
Using the Nernst equation at $298 \ K$ $(25 \ ^\circ C)$:
$E = E^o - \frac{0.0591}{n} \log \frac{1}{[Zn^{2+}]}$.
Given $E^o = -0.763 \ V$,$n = 2$,and $[Zn^{2+}] = 0.01 \ M = 10^{-2} \ M$.
$E = -0.763 - \frac{0.0591}{2} \log \frac{1}{10^{-2}}$.
$E = -0.763 - 0.02955 \times \log(10^2)$.
$E = -0.763 - 0.02955 \times 2$.
$E = -0.763 - 0.0591 = -0.8221 \ V$.
22
MediumMCQ
In a cell that utilises the reaction $Zn_{(s)} + 2H^{+}_{(aq)} \to Zn^{2+}_{(aq)} + H_{2_{(g)}}$,addition of $H_2SO_4$ to the cathode compartment will:
A
Increase the $E_{cell}$ and shift equilibrium to the right
B
Lower the $E_{cell}$ and shift equilibrium to the right
C
Lower the $E_{cell}$ and shift equilibrium to the left
D
Increase the $E_{cell}$ and shift equilibrium to the left

Solution

(A) The cell reaction is $Zn_{(s)} + 2H^{+}_{(aq)} \rightleftharpoons Zn^{2+}_{(aq)} + H_{2_{(g)}}$.
According to the Nernst equation: $E_{cell} = E^0_{cell} - \frac{0.059}{2} \log \frac{[Zn^{2+}]}{[H^{+}]^2}$.
When $H_2SO_4$ is added to the cathode compartment,the concentration of $H^{+}$ ions increases.
As $[H^{+}]$ increases,the term $\log \frac{[Zn^{2+}]}{[H^{+}]^2}$ decreases,which causes the $E_{cell}$ to increase.
According to Le Chatelier's principle,an increase in the concentration of reactants $(H^{+})$ shifts the equilibrium to the right.
23
MediumMCQ
The standard e.m.f. of a cell,involving one electron change,is found to be $0.591 \ V$ at $25 \ ^oC$. The equilibrium constant of the reaction is: $(F = 96,500 \ C \ mol^{-1}; R = 8.314 \ J \ K^{-1} \ mol^{-1})$
A
$1.0 \times 10^{10}$
B
$1.0 \times 10^{5}$
C
$1.0 \times 10^{1}$
D
$1.0 \times 10^{30}$

Solution

(A) The relationship between standard cell potential $(E_{cell}^0)$ and the equilibrium constant $(K_c)$ is given by the Nernst equation at equilibrium: $E_{cell}^0 = \frac{0.0591}{n} \log K_c$ at $298 \ K$.
Given: $E_{cell}^0 = 0.591 \ V$,$n = 1$.
Substituting the values: $0.591 = \frac{0.0591}{1} \log K_c$.
$\log K_c = \frac{0.591}{0.0591} = 10$.
$K_c = 10^{10} = 1.0 \times 10^{10}$.
24
MediumMCQ
The e.m.f. of the cell $Ag | Ag^{+}(0.1 \ M) || Ag^{+}(1 \ M) | Ag$ at $298 \ K$ is ........... $V$.
A
$0.0059$
B
$0.059$
C
$5.9$
D
$0.59$

Solution

(B) The cell reaction is: $Ag(s) + Ag^{+}(1 \ M) \rightarrow Ag^{+}(0.1 \ M) + Ag(s)$.
Using the Nernst equation: $E_{cell} = E^{\circ}_{cell} - \frac{0.0591}{n} \log \frac{[Ag^{+}]_{anode}}{[Ag^{+}]_{cathode}}$.
Here,$E^{\circ}_{cell} = E^{\circ}_{Ag^{+}/Ag} - E^{\circ}_{Ag^{+}/Ag} = 0 \ V$.
$n = 1$,$[Ag^{+}]_{anode} = 0.1 \ M$,and $[Ag^{+}]_{cathode} = 1 \ M$.
$E_{cell} = 0 - \frac{0.0591}{1} \log \frac{0.1}{1} = -0.0591 \times \log(10^{-1}) = -0.0591 \times (-1) = 0.0591 \ V$.
Rounding to the given options,the answer is $0.059 \ V$.
25
DifficultMCQ
The e.m.f. of the cell $Zn | Zn^{2+} (0.01 \ M) || Fe^{2+} (0.001 \ M) | Fe$ at $298 \ K$ is $0.2905 \ V$. The value of the equilibrium constant for the cell reaction is:
A
$0.32 / e^{0.0295}$
B
$0.32 / 10^{0.0295}$
C
$0.26 / 10^{0.0295}$
D
$0.32 / 10^{0.0591}$

Solution

(B) The cell reaction is: $Zn(s) + Fe^{2+}(aq) \to Zn^{2+}(aq) + Fe(s)$.
Using the Nernst equation: $E_{cell} = E^0_{cell} - \frac{0.0591}{n} \log \frac{[Zn^{2+}]}{[Fe^{2+}]}$.
Given $E_{cell} = 0.2905 \ V$,$n = 2$,$[Zn^{2+}] = 0.01 \ M$,and $[Fe^{2+}] = 0.001 \ M$.
$0.2905 = E^0_{cell} - \frac{0.0591}{2} \log \frac{10^{-2}}{10^{-3}} = E^0_{cell} - 0.02955 \log(10) = E^0_{cell} - 0.02955$.
$E^0_{cell} = 0.2905 + 0.02955 = 0.32005 \approx 0.32 \ V$.
At equilibrium,$E_{cell} = 0$,so $E^0_{cell} = \frac{0.0591}{n} \log K_c$.
$0.32 = \frac{0.0591}{2} \log K_c = 0.02955 \log K_c$.
$\log K_c = \frac{0.32}{0.02955} \approx \frac{0.32}{0.0295}$.
Therefore,$K_c = 10^{\frac{0.32}{0.0295}}$. Note: The provided option $B$ is represented as $10^{0.32/0.0295}$ in standard notation,but based on the provided options,$B$ is the intended choice.
26
MediumMCQ
$Zn_{(s)} + Cl_2(1 \ atm) \to Zn^{2+} + 2Cl^-$. The $E^0_{cell}$ of the cell is $2.12 \ V$. To increase $E_{cell}$:
A
$[Zn^{2+}]$ should be increased
B
$[Zn^{2+}]$ should be decreased
C
$[Cl^-]$ should be decreased
D
$P_{Cl_2}$ should be decreased

Solution

(B) According to the Nernst equation:
$E_{cell} = E^0_{cell} - \frac{0.0591}{n} \log Q$
For the reaction $Zn_{(s)} + Cl_2(1 \ atm) \to Zn^{2+} + 2Cl^-$,the reaction quotient is $Q = \frac{[Zn^{2+}][Cl^-]^2}{P_{Cl_2}}$.
Substituting $Q$ into the equation: $E_{cell} = E^0_{cell} - \frac{0.0591}{2} \log \frac{[Zn^{2+}][Cl^-]^2}{P_{Cl_2}}$.
To increase $E_{cell}$,the value of the logarithmic term must decrease,which means $Q$ must decrease.
$Q$ decreases if $[Zn^{2+}]$ is decreased,$[Cl^-]$ is increased,or $P_{Cl_2}$ is increased.
Therefore,option $B$ is correct.
27
MediumMCQ
If the standard electrode potential of $Cu^{2+}/Cu$ electrode is $0.34 \, V$,what is the electrode potential of $0.01 \, M$ concentration of $Cu^{2+}$ $(T = 298 \, K)$ (in $, V$)?
A
$0.399$
B
$0.281$
C
$0.222$
D
$0.176$

Solution

(B) The reduction half-reaction is: $Cu^{2+} + 2e^{-} \longrightarrow Cu$
Using the Nernst equation at $298 \, K$:
$E = E^0 - \frac{0.0591}{n} \log \frac{1}{[Cu^{2+}]}$
Given $E^0 = 0.34 \, V$,$n = 2$,and $[Cu^{2+}] = 0.01 \, M = 10^{-2} \, M$:
$E = 0.34 - \frac{0.0591}{2} \log \frac{1}{10^{-2}}$
$E = 0.34 - \frac{0.0591}{2} \log(10^2)$
$E = 0.34 - \frac{0.0591}{2} \times 2$
$E = 0.34 - 0.0591 = 0.2809 \, V$
Rounding to three decimal places,we get $0.281 \, V$.
28
MediumMCQ
Calculate the electrode potential at $298 \; K$ for $Zn|Zn^{2+}$ electrode in which the activity of zinc ions is $0.001 \; M$ and $E^o_{Zn^{2+}/Zn}$ is $-0.76 \; V$. (in $; V$)
A
$0.83$
B
$-0.83$
C
$-0.65$
D
$0.65$

Solution

(B) The electrode reaction is: $Zn^{2+}(aq) + 2e^{-} \rightarrow Zn(s)$.
Using the Nernst equation: $E_{Zn^{2+}/Zn} = E^o_{Zn^{2+}/Zn} - \frac{0.0591}{n} \log \frac{1}{[Zn^{2+}]}$.
Here,$n = 2$,$[Zn^{2+}] = 0.001 \; M = 10^{-3} \; M$,and $E^o_{Zn^{2+}/Zn} = -0.76 \; V$.
$E_{Zn^{2+}/Zn} = -0.76 - \frac{0.0591}{2} \log \frac{1}{10^{-3}}$.
$E_{Zn^{2+}/Zn} = -0.76 - 0.02955 \times \log(10^3)$.
$E_{Zn^{2+}/Zn} = -0.76 - 0.02955 \times 3$.
$E_{Zn^{2+}/Zn} = -0.76 - 0.08865 = -0.84865 \; V \approx -0.83 \; V$.
29
MediumMCQ
The standard $EMF$ for the given cell reaction $Zn + Cu^{2+} \rightarrow Cu + Zn^{2+}$ is $1.10 \ V$ at $25^oC$. The $EMF$ for the cell reaction,when $0.1 \ M \ Cu^{2+}$ and $0.1 \ M \ Zn^{2+}$ solutions are used,at $25^oC$ is .......... $V$.
A
$1.10$
B
$0.110$
C
$-1.10$
D
$-0.110$

Solution

(A) The $EMF$ of the cell is calculated using the $Nernst$ equation:
$E_{cell} = E_{cell}^o - \frac{0.0591}{n} \log \frac{[Zn^{2+}]}{[Cu^{2+}]}$
Here,$n = 2$ (number of electrons transferred).
Given $E_{cell}^o = 1.10 \ V$,$[Zn^{2+}] = 0.1 \ M$,and $[Cu^{2+}] = 0.1 \ M$.
Substituting these values:
$E_{cell} = 1.10 - \frac{0.0591}{2} \log \frac{0.1}{0.1}$
Since $\log(1) = 0$,the equation becomes:
$E_{cell} = 1.10 - 0 = 1.10 \ V$.
30
MediumMCQ
The oxidation potential of a hydrogen electrode at $pH = 10$ and $P_{H_2} = 1 \, atm$ is ........... $V$.
A
$0.059$
B
$0.59$
C
$0$
D
$0.51$

Solution

(B) The oxidation half-reaction for a hydrogen electrode is: $H_2(g) \rightarrow 2H^+(aq) + 2e^-$.
Using the Nernst equation for oxidation potential $(E_{OP})$:
$E_{OP} = E_{OP}^o - \frac{0.059}{n} \log \frac{[H^+]^2}{P_{H_2}}$.
Given $E_{OP}^o = 0 \, V$ for the standard hydrogen electrode,$n = 2$,$pH = 10$ (so $[H^+] = 10^{-10} \, M$),and $P_{H_2} = 1 \, atm$:
$E_{OP} = 0 - \frac{0.059}{2} \log \frac{(10^{-10})^2}{1}$.
$E_{OP} = -0.0295 \times \log(10^{-20}) = -0.0295 \times (-20) = 0.59 \, V$.
31
MediumMCQ
What is the reduction electrode potential $E$ of a $0.1 \, M$ solution of $M^{+}$ ions,given that the standard reduction potential $E^o_{RP} = -2.36 \, V$?
A
$-2.419 \, V$
B
$+0.241 \, V$
C
$-4.82 \, V$
D
None of these

Solution

(A) The Nernst equation for the reduction half-reaction $M^+ + e^- \rightarrow M$ is given by:
$E_{RP} = E^o_{RP} - \frac{0.059}{n} \log \frac{1}{[M^+]}$
Given $E^o_{RP} = -2.36 \, V$,$[M^+] = 0.1 \, M$,and $n = 1$:
$E_{RP} = -2.36 - 0.059 \log \frac{1}{0.1}$
$E_{RP} = -2.36 - 0.059 \log(10)$
Since $\log(10) = 1$:
$E_{RP} = -2.36 - 0.059 = -2.419 \, V$
32
MediumMCQ
For a cell involving a one-electron change at $25^o C$,$E^{o}_{cell} = 0.591 \ V$. The equilibrium constant for the reaction is .....
A
$1 \times 10^{10}$
B
$1 \times 10^{5}$
C
$1 \times 10^{1}$
D
$1 \times 10^{30}$

Solution

(A) The relationship between standard cell potential and equilibrium constant is given by the Nernst equation at equilibrium:
$E_{cell} = E^{o}_{cell} - \frac{0.0591}{n} \log K_c = 0$
Given:
$E^{o}_{cell} = 0.591 \ V$
$n = 1$
Substituting the values:
$0 = 0.591 - \frac{0.0591}{1} \log K_c$
$\log K_c = \frac{0.591}{0.0591} = 10$
$K_c = 10^{10}$
33
MediumMCQ
The $emf$ of the cell $Tl_{(s)} | Tl^{+}_{(aq)} (0.0001 \ M) || Cu^{2+}_{(aq)} (0.01 \ M) | Cu_{(s)}$ is $0.83 \ V$. How can the $emf$ of this cell be increased?
A
Increase the concentration of $Cu^{2+}$ ions.
B
Decrease the concentration of $Tl^{+}$ ions.
C
Increase the concentration of both.
D
Increase the concentration of $Cu^{2+}$ ions and decrease the concentration of $Tl^{+}$ ions.

Solution

(D) The cell reaction is: $2Tl_{(s)} + Cu^{2+}_{(aq)} \rightarrow 2Tl^{+}_{(aq)} + Cu_{(s)}$.
According to the Nernst equation: $E_{cell} = E^{0}_{cell} - \frac{0.0591}{n} \log \frac{[Tl^{+}]^2}{[Cu^{2+}]}$.
To increase $E_{cell}$,the value of the logarithmic term $\frac{[Tl^{+}]^2}{[Cu^{2+}]}$ must decrease.
This can be achieved by increasing the concentration of the reactant $[Cu^{2+}]$ or decreasing the concentration of the product $[Tl^{+}]$.
Therefore,both increasing $[Cu^{2+}]$ and decreasing $[Tl^{+}]$ will increase the $emf$ of the cell.
34
MediumMCQ
Calculate the $E^o_{cell}$ for the following reaction: $Cu^{+2}_{(aq)} + Sn^{+2}_{(aq)} \rightarrow Cu_{(s)} + Sn^{+4}_{(aq)}$,given that the equilibrium constant $K_c = 10^6$. (in $V$)
A
$0.1773$
B
$0.01773$
C
$0.2153$
D
$1.773$

Solution

(A) The relationship between the standard cell potential $(E^o_{cell})$ and the equilibrium constant $(K_c)$ is given by the Nernst equation at equilibrium:
$E^o_{cell} = \frac{0.0591}{n} \log K_c$
In the given reaction:
$Cu^{+2} + 2e^- \rightarrow Cu$ (Reduction)
$Sn^{+2} \rightarrow Sn^{+4} + 2e^-$ (Oxidation)
Thus,the number of electrons transferred $(n)$ is $2$.
Given $K_c = 10^6$ and $n = 2$:
$E^o_{cell} = \frac{0.0591}{2} \log(10^6)$
$E^o_{cell} = 0.02955 \times 6$
$E^o_{cell} = 0.1773 \ V$
35
MediumMCQ
For a redox reaction,$Oxi + ne^- \rightarrow Red$,what is the correct form of the Nernst equation?
A
$E_{cell} = E_{cell}^\circ + \frac{RT}{nF} \ln \frac{[Red]}{[Oxi]}$
B
$E_{cell} = E_{cell}^\circ - \frac{RT}{nF} \ln \frac{[Red]}{[Oxi]}$
C
$E_{cell} = E_{cell}^\circ - \frac{RT}{nF} \ln \frac{[Oxi]}{[Red]}$
D
$E_{cell} = E_{cell}^\circ + \frac{RT}{nF} \ln \frac{[Oxi]}{[Red]}$

Solution

(B) The Nernst equation for a general redox reaction $aA + bB \rightarrow cC + dD$ is given by $E_{cell} = E_{cell}^\circ - \frac{RT}{nF} \ln Q$,where $Q$ is the reaction quotient.
For the half-reaction $Oxi + ne^- \rightarrow Red$,the reaction quotient $Q$ is defined as $\frac{[Red]}{[Oxi]}$.
Substituting this into the Nernst equation,we get $E_{cell} = E_{cell}^\circ - \frac{RT}{nF} \ln \frac{[Red]}{[Oxi]}$.
Alternatively,using the property of logarithms,$-\ln \frac{[Red]}{[Oxi]} = \ln \frac{[Oxi]}{[Red]}$,so $E_{cell} = E_{cell}^\circ + \frac{RT}{nF} \ln \frac{[Oxi]}{[Red]}$.
36
MediumMCQ
For the cell reaction $Zn_{(s)} + Ni^{2+}_{(aq)} (a = 0.1) \rightarrow Zn^{2+}_{(aq)} (a = 1.0) + Ni_{(s)}$ at $298 \ K$,the $emf$ is observed to be $0.5105 \ V$. What is the standard $emf$ $(E^{\circ}_{cell})$ of the cell in $V$?
A
$-0.5105$
B
$0.5400$
C
$0.4810$
D
$0.5696$

Solution

(B) The Nernst equation for the cell reaction is given by:
$E_{cell} = E^{\circ}_{cell} - \frac{0.059}{n} \log \frac{[Zn^{2+}]}{[Ni^{2+}]}$
Here,$n = 2$ (number of electrons transferred).
Substituting the given values:
$0.5105 = E^{\circ}_{cell} - \frac{0.059}{2} \log \frac{1.0}{0.1}$
$0.5105 = E^{\circ}_{cell} - 0.0295 \log(10)$
Since $\log(10) = 1$,we have:
$0.5105 = E^{\circ}_{cell} - 0.0295$
$E^{\circ}_{cell} = 0.5105 + 0.0295 = 0.5400 \ V$
37
MediumMCQ
For the cell $Zn | Zn^{2+}_{(aq)} || Cu^{2+}_{(aq)} | Cu$,the standard cell potential $E^o$ is $1.10 \ V$ at $25^o \ C$. What is the order of magnitude of the equilibrium constant $K$ for the reaction $Zn + Cu^{2+}_{(aq)} \rightleftharpoons Cu + Zn^{2+}_{(aq)}$?
A
$10^{+28}$
B
$10^{+37}$
C
$10^{+18}$
D
$10^{+17}$

Solution

(B) The relationship between standard cell potential $E^o_{cell}$ and equilibrium constant $K$ is given by the Nernst equation at $25^o \ C$ (or $298 \ K$):
$E^o_{cell} = \frac{0.059}{n} \log K$
Here,$n = 2$ (number of electrons transferred in the redox reaction).
Given $E^o_{cell} = 1.10 \ V$.
Substituting the values:
$1.10 = \frac{0.059}{2} \log K$
$\log K = \frac{1.10 \times 2}{0.059} = \frac{2.20}{0.059} \approx 37.288$
$K = 10^{37.288} \approx 10^{+37}$
38
MediumMCQ
The standard $emf$ for the cell reaction $Zn_{(s)} + Cu^{2+}_{(aq)} \rightarrow Zn^{2+}_{(aq)} + Cu_{(s)}$ is $1.10 \, V$ at $25 \, ^\circ C$. What will be the $emf$ of the cell when using $0.1 \, M \, Cu^{2+}$ and $0.1 \, M \, Zn^{2+}$ solutions (in $, V$)?
A
$1.10$
B
$0.110$
C
$-1.10$
D
$-0.110$

Solution

(A) The Nernst equation for the cell reaction is given by:
$E_{cell} = E^\circ_{cell} - \frac{0.059}{n} \log \frac{[Zn^{2+}]}{[Cu^{2+}]}$
Here,$n = 2$ (number of electrons transferred).
Given: $E^\circ_{cell} = 1.10 \, V$,$[Zn^{2+}] = 0.1 \, M$,and $[Cu^{2+}] = 0.1 \, M$.
Substituting the values:
$E_{cell} = 1.10 - \frac{0.059}{2} \log \frac{0.1}{0.1}$
Since $\log(1) = 0$,the term $\frac{0.059}{2} \log(1) = 0$.
Therefore,$E_{cell} = 1.10 - 0 = 1.10 \, V$.
39
MediumMCQ
Calculate the equilibrium constant for the cell reaction at $298 \ K$: $Cu_{(s)} + 2Ag^{+}_{(aq)} \rightarrow Cu^{2+}_{(aq)} + 2Ag_{(s)}$,given $E^{0}_{cell} = 0.46 \ V$.
A
$2.0 \times 10^{10}$
B
$4.0 \times 10^{10}$
C
$4 \times 10^{15}$
D
$2.4 \times 10^{10}$

Solution

(C) The relationship between the equilibrium constant $K$ and the standard cell potential $E^{0}_{cell}$ is given by:
$E^{0}_{cell} = \frac{0.0591}{n} \log K$ at $298 \ K$.
Here,$n = 2$ (number of electrons transferred).
$0.46 = \frac{0.0591}{2} \log K$
$\log K = \frac{0.46 \times 2}{0.0591} = \frac{0.92}{0.0591} \approx 15.567$.
$K = \text{antilog}(15.567) \approx 3.69 \times 10^{15} \approx 4 \times 10^{15}$.
40
MediumMCQ
What is the change in the reduction potential of a hydrogen electrode when the $pH$ of the initial solution changes from $0$ to $7$ by neutralization?
A
Increases by $0.059 \, V$
B
Decreases by $0.059 \, V$
C
Increases by $0.413 \, V$
D
Decreases by $0.413 \, V$

Solution

(C) The reduction reaction for a hydrogen electrode is: $2H^+ (aq) + 2e^- \rightarrow H_2 (g)$.
Using the Nernst equation at $298 \, K$: $E_{H^+/H_2} = E^0_{H^+/H_2} - \frac{0.0591}{1} \log \frac{1}{[H^+]}$.
Since $E^0_{H^+/H_2} = 0 \, V$ and $pH = -\log[H^+]$,the equation becomes: $E = 0.0591 \times pH$.
For $pH_1 = 0$: $E_1 = 0.0591 \times 0 = 0 \, V$.
For $pH_2 = 7$: $E_2 = 0.0591 \times 7 = 0.4137 \, V$.
Change in potential $\Delta E = E_2 - E_1 = 0.4137 - 0 = 0.4137 \, V$.
Since the potential increases from $0 \, V$ to $0.4137 \, V$,it increases by $0.413 \, V$.
41
EasyMCQ
What is the oxidation potential of $0.05 \, M \, H_2SO_4$ in volts?
A
$-2 \times 0.05912$
B
$-0.01 \times 0.05912$
C
$-2.321 \times 0.05912$
D
$+1 \times 0.05912$

Solution

(D) For $H_2SO_4$,the concentration of $H^+$ ions is $[H^+] = 2 \times 0.05 = 0.1 \, M$.
The oxidation half-reaction is $\frac{1}{2} H_2 \to H^+ + e^-$.
Using the Nernst equation for oxidation potential:
$E_{ox} = E^0_{ox} - \frac{0.05912}{n} \log [H^+]$.
Since $E^0_{ox}$ for hydrogen is $0 \, V$ and $n = 1$:
$E_{ox} = 0 - 0.05912 \log(0.1) = -0.05912 \times (-1) = +0.05912 \, V$.
This can be expressed as $+1 \times 0.05912 \, V$.
42
EasyMCQ
What is the potential of the cell for the reaction $Zn + Cu^{+2} \,(1 \, M) \rightarrow Cu + Zn^{+2} \,(1 \, M)$ at $25^{\circ}C$ (in $, V$)?
A
$1.1$
B
$0.1$
C
$-1.1$
D
$-0.11$

Solution

(A) The standard cell potential for the Daniel cell is given by $E^0_{cell} = E^0_{cathode} - E^0_{anode} = 0.34 \, V - (-0.76 \, V) = 1.1 \, V$.
Using the Nernst equation: $E_{cell} = E^0_{cell} - \frac{0.0592}{n} \log \frac{[Zn^{+2}]}{[Cu^{+2}]}$.
Since the concentrations of both ions are $1 \, M$,the reaction quotient $Q = \frac{1}{1} = 1$.
Therefore,$E_{cell} = 1.1 \, V - \frac{0.0592}{2} \log(1)$.
Since $\log(1) = 0$,the equation becomes $E_{cell} = 1.1 \, V - 0 = 1.1 \, V$.
43
EasyMCQ
If the concentration of a $Zn^{2+}$ solution is diluted $10$ times,what is the change in the potential of the $Zn/Zn^{2+}$ electrode?
A
$0.03 \, V$ increase
B
$0.03 \, V$ decrease
C
$0.059 \, V$ increase
D
$0.059 \, V$ decrease

Solution

(A) The Nernst equation for the $Zn/Zn^{2+}$ electrode is given by: $E_{Zn/Zn^{2+}} = E^{\circ}_{Zn/Zn^{2+}} - \frac{0.059}{2} \log [Zn^{2+}]$.
When the concentration is diluted $10$ times,the new concentration becomes $[Zn^{2+}]' = \frac{[Zn^{2+}]}{10}$.
The new potential is $E' = E^{\circ}_{Zn/Zn^{2+}} - \frac{0.059}{2} \log \left( \frac{[Zn^{2+}]}{10} \right)$.
$E' = E^{\circ}_{Zn/Zn^{2+}} - \frac{0.059}{2} (\log [Zn^{2+}] - \log 10)$.
$E' = E^{\circ}_{Zn/Zn^{2+}} - \frac{0.059}{2} \log [Zn^{2+}] + \frac{0.059}{2} \log 10$.
Since $\log 10 = 1$,we get $E' = E_{Zn/Zn^{2+}} + \frac{0.059}{2} = E_{Zn/Zn^{2+}} + 0.0295 \, V \approx E_{Zn/Zn^{2+}} + 0.03 \, V$.
Thus,the potential increases by $0.03 \, V$.
44
EasyMCQ
In a cell reaction,a $2$ electron change occurs. The standard $e.m.f.$ of the cell at $25^\circ C$ is $0.295 \ V$. What is the equilibrium constant for the reaction at $25^\circ C$?
A
$10$
B
$1 \times 10^{10}$
C
$1 \times 10^{-10}$
D
$29.5 \times 10^{-2}$

Solution

(B) The relationship between the standard cell potential $(E_{cell}^\circ)$ and the equilibrium constant $(K_{eq})$ is given by the Nernst equation at $25^\circ C$ $(298 \ K)$:
$E_{cell}^\circ = \frac{0.0591}{n} \log K_{eq}$
Given: $n = 2$,$E_{cell}^\circ = 0.295 \ V$.
Substituting the values:
$0.295 = \frac{0.0591}{2} \log K_{eq}$
$0.295 = 0.02955 \log K_{eq}$
$\log K_{eq} = \frac{0.295}{0.02955} \approx 10$
$K_{eq} = 10^{10}$
45
EasyMCQ
Considering the reaction $Cl_{2(g)} + 2Br^{-}_{(aq)} \rightarrow 2Cl^{-}_{(aq)} + Br_{2(l)}$,calculate the cell $emf$ in $V$ when $[Cl^{-}] = [Br_2] = [Br^{-}] = 0.01 \ M$ and $Cl_2$ gas is at $1 \ atm$ pressure. (Given $E^o = 0.29 \ V$ for the reaction)
A
$0.54$
B
$0.35$
C
$0.24$
D
$-0.29$

Solution

(B) The Nernst equation for the reaction is: $E_{cell} = E^o_{cell} - \frac{0.059}{n} \log \frac{[Cl^{-}]^2 [Br_2]}{P_{Cl_2} [Br^{-}]^2}$
Here,$n = 2$,$E^o_{cell} = 0.29 \ V$,$[Cl^{-}] = 0.01 \ M$,$[Br_2] = 0.01 \ M$,$[Br^{-}] = 0.01 \ M$,and $P_{Cl_2} = 1 \ atm$.
Substituting the values: $E_{cell} = 0.29 - \frac{0.059}{2} \log \frac{(0.01)^2 (0.01)}{1 \times (0.01)^2}$
$E_{cell} = 0.29 - 0.0295 \log(0.01)$
$E_{cell} = 0.29 - 0.0295 \times (-2) = 0.29 + 0.059 = 0.349 \ V \approx 0.35 \ V$.
46
DifficultMCQ
Calculate the $EMF$ of the cell: $Cr | Cr^{+3}(0.1 \, M) || Fe^{+2}(0.01 \, M) | Fe$
(Given: $E^o_{Cr^{+3}|Cr} = -0.75 \, V$,$E^o_{Fe^{+2}|Fe} = -0.45 \, V$) (in $, V$)
A
$0.26$
B
$0.31$
C
$0.45$
D
$0.58$

Solution

(A) The cell reaction is:
Anode: $2Cr \to 2Cr^{+3} + 6e^-$
Cathode: $3Fe^{+2} + 6e^- \to 3Fe$
Overall reaction: $2Cr + 3Fe^{+2} \to 2Cr^{+3} + 3Fe$
Number of electrons transferred $(n)$ = $6$.
Standard cell potential $E^o_{cell} = E^o_{cathode} - E^o_{anode} = -0.45 - (-0.75) = 0.30 \, V$.
Using the Nernst equation:
$E_{cell} = E^o_{cell} - \frac{0.059}{n} \log \frac{[Cr^{+3}]^2}{[Fe^{+2}]^3}$
$E_{cell} = 0.30 - \frac{0.059}{6} \log \frac{(0.1)^2}{(0.01)^3}$
$E_{cell} = 0.30 - \frac{0.059}{6} \log \frac{10^{-2}}{10^{-6}}$
$E_{cell} = 0.30 - \frac{0.059}{6} \log (10^4)$
$E_{cell} = 0.30 - \frac{0.059 \times 4}{6} = 0.30 - 0.0393 \approx 0.26 \, V$.
47
MediumMCQ
For the cell reaction $Zn + Cu^{2+} \rightarrow Cu + Zn^{2+}$,the standard $EMF$ value at $25^{\circ}C$ is $1.10 \ V$. If $0.1 \ M \ Cu^{2+}$ and $0.1 \ M \ Zn^{2+}$ solutions are used,the $EMF$ will be .......... $V$.
A
$1.10$
B
$0.110$
C
$-1.10$
D
$-0.110$

Solution

(A) The Nernst equation for the cell reaction is given by:
$E_{cell} = E^{\circ}_{cell} - \frac{0.059}{n} \log \frac{[Zn^{2+}]}{[Cu^{2+}]}$
Here,$n = 2$,$E^{\circ}_{cell} = 1.10 \ V$,$[Zn^{2+}] = 0.1 \ M$,and $[Cu^{2+}] = 0.1 \ M$.
Substituting these values:
$E_{cell} = 1.10 - \frac{0.059}{2} \log \frac{0.1}{0.1}$
$E_{cell} = 1.10 - 0.0295 \log(1)$
Since $\log(1) = 0$,we get:
$E_{cell} = 1.10 - 0 = 1.10 \ V$.
48
EasyMCQ
For the reaction $A_{(s)} + 2B^{+}_{(aq)} \rightarrow A^{2+}_{(aq)} + 2B_{(s)}$,the value of $K_c$ is $10^{12}$. What is the value of $E^o_{cell}$ (in $, V$)?
A
$0.354$
B
$0.708$
C
$0.0098$
D
$1.36$

Solution

(A) The relationship between the standard cell potential $E^o_{cell}$ and the equilibrium constant $K_c$ is given by the Nernst equation at equilibrium:
$E^o_{cell} = \frac{0.0591}{n} \log K_c$
Here,the number of electrons transferred $n = 2$ (from $A \rightarrow A^{2+} + 2e^-$ and $2B^+ + 2e^- \rightarrow 2B$).
Given $K_c = 10^{12}$.
Substituting the values:
$E^o_{cell} = \frac{0.0591}{2} \log(10^{12})$
$E^o_{cell} = 0.02955 \times 12$
$E^o_{cell} = 0.3546 \, V$
Thus,the correct value is approximately $0.354 \, V$.
49
DifficultMCQ
The $EMF$ of the following three galvanic cells are $E_1, E_2$ and $E_3$ respectively. Which of the following is correct?
$(i)$ $Zn | Zn^{2+} (1 \ M) || Cu^{2+} (0.1 \ M) | Cu$
$(ii)$ $Zn | Zn^{2+} (1 \ M) || Cu^{2+} (1 \ M) | Cu$
$(iii)$ $Zn | Zn^{2+} (0.1 \ M) || Cu^{2+} (1 \ M) | Cu$
A
$E_2 > E_3 > E_1$
B
$E_3 > E_2 > E_1$
C
$E_1 > E_2 > E_3$
D
$E_1 > E_3 > E_2$

Solution

(B) The $EMF$ of a galvanic cell is given by the Nernst equation:
$E_{cell} = E^{\circ}_{cell} - \frac{0.059}{2} \log \left( \frac{[Zn^{2+}]}{[Cu^{2+}]} \right)$
For the given cells,$E^{\circ}_{cell}$ is constant. The value of $E_{cell}$ decreases as the ratio $Q = \frac{[Zn^{2+}]}{[Cu^{2+}]}$ increases.
$(i)$ $Q_1 = \frac{1}{0.1} = 10 \implies \log(Q_1) = 1$
$(ii)$ $Q_2 = \frac{1}{1} = 1 \implies \log(Q_2) = 0$
$(iii)$ $Q_3 = \frac{0.1}{1} = 0.1 \implies \log(Q_3) = -1$
Since $\log(Q_3) < \log(Q_2) < \log(Q_1)$,it follows that $E_3 > E_2 > E_1$.

Electrochemistry — Nernst equation and ECS · Frequently Asked Questions

1Are these Electrochemistry questions useful for JEE and NEET?

Yes. All questions in this section are mapped to JEE Main and NEET exam patterns. Previous year questions from JEE Main, NEET, GUJCET and state-level exams are included with full solutions.

2Can I switch to Hindi or Gujarati for these questions?

Yes. Use the language tabs in the hero section or the sidebar to view the same questions and solutions in English, Hindi or Gujarati.

3How do I generate a question paper from this subtopic?

Use the Vedclass Exam Paper Generator — select the chapter and subtopic, set difficulty, and generate Sets A, B, C, D automatically. First 3 chapters of every subject are free.

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D papers from this chapter in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo
For Teachers & Institutes

Generate a Electrochemistry Exam Paper in 2 Minutes

Select subtopic & difficulty — Sets A, B, C, D auto-generated with No Repeat logic.

First 3 chapters of every subject are free — no payment required.