Electrochemistry · JEE Main previous year questions

In a cell, the following reactions take place ${\mathrm{Fe}}^{2+}\to {\mathrm{Fe}}^{3+}+e^{-}{E}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}^{\circ }=0.77\text{ V}$ $2{\mathrm{I}}^{-}\to {\mathrm{I}}_2+2e^{-}{E}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}^{\circ }=0.54\text{ V}$ The standard electrode potential for the spontaneous reaction in the cell is $x\times 10^{-2}\text{ V}$ at $298\text{ K}$. The value of $x$ is $\underline{}$. (Nearest Integer)

Given below are two statements. Statement I : During electrolytic refining, blister copper deposits precious metals. Statement II : In the process of obtaining pure copper by electrolysis method, copper blister is used to make the anode. In the light of the above statements, choose the correct from the options given below.

1. A.Both Statement I and Statement II are true.
2. B.Both Statement I and Statement II are false.
3. C.Statement I is true but Statement II is false.
4. D.Statement I is false but Statement II is true.

The resistance of a conductivity cell containing $0.01\text{ M }\mathrm{KCl}$ solution at $298\text{ K}$ is $1750\Omega$. If the conductivity of $0.01\text{ M }\mathrm{KCl}$ solution at $298\text{ K}$ is $0.152\times 10^{-3}{\text{ S cm}}^{-1}$, then the cell constant of the conductivity cell is $\underline{}\times 10^{-3}{\text{ cm}}^{-1}$.

If the conductivity of mercury at $0^{\circ }\mathrm{C}$ is $1.07\times 10^6\mathrm{S}{\mathrm{m}}^{-1}$ and the resistance of a cell containing mercury is $0.243\Omega$, then the cell constant of the cell is $x\times 10^4{\mathrm{m}}^{-1}$. The value of x is ____. (Nearest integer)

For the galvanic cell, $\mathrm{Zn}(\mathrm{s})+\mathrm{C}{\mathrm{u}}^{2+}(0.02\mathrm{M})\to \mathrm{Z}{\mathrm{n}}^{2+}(0.04\mathrm{M})+\mathrm{Cu}(\mathrm{s})$, ${\mathrm{E}}_{\mathrm{cell}}=$ ___________ $\times 10^{-2}\text{ V}$. (Nearest integer) [$\text{Use : }{E}_{Cu/C{\mathrm{u}}^{2+}}^0=-0.34\text{ V}$, $E_{Zn/Z{\mathrm{n}}^{2+}}^0=+0.76\text{ V}$, $\frac{2.303RT}{F}=0.059\text{ V}$]

For the cell $\mathrm{Cu}(\mathrm{s})\mid \mathrm{C}{\mathrm{u}}^{2+}(\mathrm{aq})(0.1\mathrm{M})\parallel \mathrm{A}{\mathrm{g}}^{+}(\mathrm{aq})(0.01\mathrm{M})\mid \mathrm{Ag}(\mathrm{s})$ the cell potential ${\mathrm{E}}_1=0.3095\mathrm{V}$ For the cell $\mathrm{Cu}(\mathrm{s})\mid \mathrm{C}{\mathrm{u}}^{2+}(\mathrm{aq})(0.01\mathrm{M})\parallel \mathrm{A}{\mathrm{g}}^{+}(\mathrm{aq})(0.001\mathrm{M})\mid \mathrm{Ag}(\mathrm{s})$ the cell potential = __________ $\times 10^{-2}\text{ V}$. (Round off to the nearest integer). $\left[Use:\frac{2.303RT}{F}=0.059\right]$

Consider the cell at $25^{\circ }\mathrm{C}$ $\mathrm{Zn}\mid \mathrm{Z}{\mathrm{n}}^{2+}(\mathrm{aq}),(1M)\parallel \mathrm{F}{\mathrm{e}}^{3+}(\mathrm{aq}),\mathrm{F}{\mathrm{e}}^{2+}(\mathrm{aq})\mid \mathrm{Pt}(\mathrm{s})$ The fraction of total iron present as $\mathrm{F}{\mathrm{e}}^{3+}$ ion at the cell potential of 1.500 V is $x\times 10^{-2}$. The value of x is ____. (Nearest integer) (Given : $E_{F{e}^{3+}/F{e}^{2+}}^0=0.77V$, $E_{Z{n}^{2+}/Zn}^0=-0.76V$)

The molar conductivities at infinite dilution of barium chloride, sulphuric acid and hydrochloric acid are 280, 860 and $426\mathrm{S}\mathrm{c}{\mathrm{m}}^2\mathrm{mo}{\mathrm{l}}^{-1}$ respectively. The molar conductivity at infinite dilution of barium sulphate is ____ $\mathrm{S}\mathrm{c}{\mathrm{m}}^2\mathrm{mo}{\mathrm{l}}^{-1}$. (Round off to the Nearest Integer ).

Given below are two statements : Statement I : The ${\mathrm{E}}^{\circ }$ value for $\mathrm{C}{\mathrm{e}}^{4+}/C{\mathrm{e}}^{3+}$ is $+1.74\text{ V}$. Statement II : $\mathrm{Ce}$ is more stable in $\mathrm{C}{\mathrm{e}}^{4+}$ state than $\mathrm{C}{\mathrm{e}}^{3+}$ state. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Statement I is incorrect but statement II is correct
2. B.Both statement I and statement II are correct
3. C.Both statement I and statement II are incorrect
4. D.Statement I is correct but statement II is incorrect

Statements about heavy water are given below : A. Heavy water is used in exchange reactions for the study of reaction mechanisms. B. Heavy water is prepared by exhaustive electrolysis of water. (C) Heavy water has higher boiling point than ordinary water. (D) Viscosity of ${\mathrm{H}}_2\mathrm{O}$ is greater than ${\mathrm{D}}_2\mathrm{O}$. Choose the most appropriate answer from the options given below :

1. A.A, B, and C only
2. B.A and C only
3. C.A and D only
4. D.A and B only

Consider the following reaction $Mn{O}_4^{-}+8H^{+}+5e^{-}\to M{n}^{+2}+4H_{2}O,E^o=1.51V$. The quantity of electricity required in Faraday to reduce five moles of $Mn{O}_4^{-}$ is _________. (Integer answer)

Potassium chlorate is prepared by the electrolysis of $\mathrm{KCl}$ in basic solution $$6O{\mathrm{H}}^{-}+\mathrm{C}{\mathrm{l}}^{-}\to \mathrm{Cl}{\mathrm{O}}_3^{-}+3{\mathrm{H}}_2\mathrm{O}+6{\mathrm{e}}^{-}$$ If only $60\%$ of the current is utilized in the reaction, the time (rounded to the nearest hour) required to produce $10\text{ g}$ of $\mathrm{KCl}{\mathrm{O}}_3$ using a current of $2\text{ A}$ is ______ . (Given : $F=96,500\mathrm{C}\mathrm{mo}{\mathrm{l}}^{-1}$; molar mass of $\mathrm{KCl}{\mathrm{O}}_3=122\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$)

Let ${\mathrm{C}}_{\mathrm{NaCl}}$ and ${\mathrm{C}}_{\mathrm{BaS}{\mathrm{O}}_4}$ be the conductances (in S) measured for saturated aqueous solutions of $\mathrm{NaCl}$ and $\mathrm{BaS}{\mathrm{O}}_4$, respectively, at a temperature T. Which of the following is false?

1. A.Ionic mobilities of ions from both salts increase with T.
2. B.${\mathrm{C}}_{\mathrm{NaCl}}({\mathrm{T}}_2)>{\mathrm{C}}_{\mathrm{NaCl}}({\mathrm{T}}_1)$ for ${\mathrm{T}}_2>{\mathrm{T}}_1$
3. C.${\mathrm{C}}_{\mathrm{BaS}{\mathrm{O}}_4}({\mathrm{T}}_2)>{\mathrm{C}}_{\mathrm{BaS}{\mathrm{O}}_4}({\mathrm{T}}_1)$ for ${\mathrm{T}}_2>{\mathrm{T}}_1$
4. D.${\mathrm{C}}_{\mathrm{NaCl}}\gg {\mathrm{C}}_{\mathrm{BaS}{\mathrm{O}}_4}$ at a given T

108 g of silver (molar mass $108{\text{ g mol}}^{-1}$) is deposited at cathode from $\mathrm{AgN}{\mathrm{O}}_3(\mathrm{aq})$ solution by a certain quantity of electricity. The volume (in L) of oxygen gas produced at 273 K and 1 bar pressure from water by the same quantity of electricity is _______.

Amongst the following, the form of water with the lowest ionic conductance at 298 K is :

1. A.saline water used for intravenous injection
2. B.sea water
3. C.distilled water
4. D.water from a well

What would be the electrode potential for the given half cell reaction at pH = 5? _______. $$2{\mathrm{H}}_2\mathrm{O}\to {\mathrm{O}}_2+4{\mathrm{H}}^{\oplus }+4e^{-};E_{\mathrm{red}}^0=1.23\text{ V}$$ $(\mathrm{R}=8.314{\text{ J mol}}^{-1}{\text{ K}}^{-1};\text{Temp}=298\text{ K}$; oxygen under std. atm. pressure of 1 bar)

Given that the standard potentials $(E^{\circ })$ of $\mathrm{C}{\mathrm{u}}^{2+}/Cu$ and $\mathrm{C}{\mathrm{u}}^{+}/Cu$ are $0.34\text{ V}$ and $0.522\text{ V}$ respectively, the $E^{\circ }$ of $\mathrm{C}{\mathrm{u}}^{2+}/C{\mathrm{u}}^{+}$ :

1. A.$-0.182\text{ V}$
2. B.$-0.158\text{ V}$
3. C.$0.182\text{ V}$
4. D.$+0.158\text{ V}$

Given ${\text{Co}}^{3+}+e^{-}\to {\text{Co}}^{2+};{\text{E}}^{\circ }=+1.81\text{ V}$ ${\text{Pb}}^{4+}+2e^{-}\to {\text{Pb}}^{2+};{\text{E}}^{\circ }=+1.67\text{ V}$ ${\text{Ce}}^{4+}+e^{-}\to {\text{Ce}}^{3+};{\text{E}}^{\circ }=+1.61\text{ V}$ ${\text{Bi}}^{3+}+3e^{-}\to \text{Bi};{\text{E}}^{\circ }=+0.20\text{ V}$ Oxidizing power of the species will increase in the order :

1. A.${\text{Co}}^{3+}<{\text{Ce}}^{4+}<{\text{Bi}}^{3+}<{\text{Pb}}^{4+}$
2. B.${\text{Co}}^{3+}<{\text{Pb}}^{4+}<{\text{Ce}}^{4+}<{\text{Bi}}^{3+}$
3. C.${\text{Ce}}^{4+}<{\text{Pb}}^{4+}<{\text{Bi}}^{3+}<{\text{Co}}^{3+}$
4. D.${\text{Bi}}^{3+}<{\text{Ce}}^{4+}<{\text{Pb}}^{4+}<{\text{Co}}^{3+}$

The decreasing order of electrical conductivity of the following aqueous solutions is : 0.1 M Formic acid (A), 0.1 M Acetic acid (B), 0.1 M Benzoic acid (C)

1. A.A > B > C
2. B.C > B > A
3. C.A > C > B
4. D.C > A > B

Consider the statements S1 and S2 S1 : Conductivity always increases with decrease in the concentration of electrolyte. S2 : Molar conductivity always increases with decrease in the concentration of electrolyte. The correct option among the following is :

1. A.Both S1 and S2 are wrong
2. B.S1 is correct and S2 is wrong
3. C.Both S1 and S2 are correct
4. D.S1 is wrong and S2 is correct

1. A.
2. B.
3. C.
4. D.

The standard Gibbs energy for the given cell reaction in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ at 298 K is : $\mathrm{Zn}(\mathrm{s})+\mathrm{C}{\mathrm{u}}^{2+}(\mathrm{aq})\to \mathrm{Z}{\mathrm{n}}^{2+}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$, E° = 2 V at 298 K (Faraday's constant, $F=96000\mathrm{C}\mathrm{mo}{\mathrm{l}}^{-1}$)

1. A.384
2. B.−192
3. C.−384
4. D.192

A solution of $\mathrm{Ni}(\mathrm{N}{\mathrm{O}}_3{)}_2$ is electrolysed between platinum electrodes using 0.1 Faraday electricity. How many moles of Ni will be deposited at the cathode?

1. A.0.10
2. B.0.15
3. C.0.20
4. D.0.05

Calculate the standard cell potential in (V) of the cell in which following reaction takes place : $\mathrm{F}{\mathrm{e}}^{2+}(\mathrm{aq})+\mathrm{A}{\mathrm{g}}^{+}(\mathrm{aq})\to \mathrm{F}{\mathrm{e}}^{3+}(\mathrm{aq})+\mathrm{Ag}(\mathrm{s})$ Given that $E_{\mathrm{A}{\mathrm{g}}^{+}/Ag}^o=x\mathrm{V}$ $E_{\mathrm{F}{\mathrm{e}}^{2+}/Fe}^o=y\mathrm{V}$ $E_{\mathrm{F}{\mathrm{e}}^{3+}/Fe}^o=z\mathrm{V}$

1. A.x + 2y − 3z
2. B.x − z
3. C.x − y
4. D.x + y − z

The standard electrode potential $E^o$ and its temperature coefficient $\left(\frac{d{E}^o}{dT}\right)$ for a cell are 2V and $-5\times 10^{-4}\mathrm{V}{\mathrm{K}}^{-1}$ at 300 K respectively. The cell reaction is $\mathrm{Zn}(\mathrm{s})+\mathrm{C}{\mathrm{u}}^{2+}(\mathrm{aq})⟶\mathrm{Z}{\mathrm{n}}^{2+}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$ The standard reaction enthalpy $({\Delta }_{\mathrm{r}}{H}^o)$ at 300 K in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ is, [Use $\mathrm{R}=8\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ and $\mathrm{F}=96,000C\mathrm{mo}{\mathrm{l}}^{-1}$]

1. A.$-412.8$
2. B.$-384.0$
3. C.$192.0$
4. D.$206.4$