Electrochemistry · JEE Main previous year questions

${\mathrm{O}}_2$ gas will be evolved as a product of electrolysis of : (A) an aqueous solution of $\mathrm{AgN}{\mathrm{O}}_3$ using silver electrodes. (B) an aqueous solution of $\mathrm{AgN}{\mathrm{O}}_3$ using platinum electrodes. (C) a dilute solution of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ using platinum electrodes. (D) a high concentration solution of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ using platinum electrodes. Choose the correct answer from the options given below :

1. A.(B) and (C) only
2. B.(B) and (D) only
3. C.(A) and (D) only
4. D.(A) and (C) only

For the given cell $\mathrm{F}{\mathrm{e}}^{2+}(\mathrm{aq})+\mathrm{A}{\mathrm{g}}_{(\mathrm{aq})}^{+}\to \mathrm{F}{\mathrm{e}}^{3+}(\mathrm{aq})+\mathrm{A}{\mathrm{g}}_{(\mathrm{s})}$ The standard cell potential of the above reaction is Given: $\mathrm{A}{\mathrm{g}}^{+}+{\mathrm{e}}^{-}\to \mathrm{Ag}{\mathrm{E}}^{\theta }=\mathrm{xV}$ $\mathrm{F}{\mathrm{e}}^{2+}+2{\mathrm{e}}^{-}\to \mathrm{Fe}{\mathrm{E}}^{\theta }=\mathrm{yV}$ $\mathrm{F}{\mathrm{e}}^{3+}+3{\mathrm{e}}^{-}\to \mathrm{Fe}{\mathrm{E}}^{\theta }=\mathrm{zV}$

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

Standard electrode potentials for a few half cells are mentioned below : ${\mathrm{E}}_{\mathrm{C}{\mathrm{u}}^{2+}/Cu}^{\circ }=0.34\mathrm{V}$, ${\mathrm{E}}_{\mathrm{Z}{\mathrm{n}}^{2+}/Zn}^{\circ }=-0.76\mathrm{V}$ ${\mathrm{E}}_{\mathrm{A}{\mathrm{g}}^{+}/Ag}^{\circ }=0.80\mathrm{V}$, ${\mathrm{E}}_{\mathrm{M}{\mathrm{g}}^{2+}/Mg}^{\circ }=-2.37\mathrm{V}$ Which one of the following cells gives the most negative value of $\Delta {\mathrm{G}}^{\circ }$ ?

1. A.$Zn|Z{\mathrm{n}}^{2+}(1M)||A{\mathrm{g}}^{+}(1M)|Ag$
2. B.$Ag|A{\mathrm{g}}^{+}(1M)||M{\mathrm{g}}^{2+}(1M)|Mg$
3. C.$Zn|Z{\mathrm{n}}^{2+}(1M)||M{\mathrm{g}}^{2+}(1M)|Mg$
4. D.$Cu|C{\mathrm{u}}^{2+}(1M)||A{\mathrm{g}}^{+}(1M)|Ag$

Which of the following electrolyte can be used to obtain ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8$ by the process of electrolysis ?

1. A.Concentrated solution of sulphuric acid
2. B.Dilute solution of sodium sulphate.
3. C.Acidified dilute solution of sodium sulphate.
4. D.Dilute solution of sulphuric acid

A solution of aluminium chloride is electrolysed for 30 minutes using a current of 2 A . The amount of the aluminium deposited at the cathode is _________ . [Given : molar mass of aluminium and chlorine are $27{\text{ g mol}}^{-1}$ and $35.5{\text{ g mol}}^{-1}$ respectively. Faraday constant $=96500{\text{ C mol}}^{-1}$]

1. A.$1.660\text{ g}$
2. B.$1.007\text{ g}$
3. C.$0.336\text{ g}$
4. D.$0.441\text{ g}$

1. A.A - weak electrolyte B - weak electrolyte
2. B.A - weak electrolyte B - strong electrolyte
3. C.A - strong electrolyte B - strong electrolyte
4. D.A - strong electrolyte B - weak electrolyte

The standard reduction potentials at $298\text{ K}$ for the following half cells are given below : $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}+14{\mathrm{H}}^{+}+6{\mathrm{e}}^{-}\to 2C{\mathrm{r}}^{3+}+7{\mathrm{H}}_2\mathrm{O},{\mathrm{E}}^{\circ }=1.33\mathrm{V}$ $\mathrm{F}{\mathrm{e}}^{3+}(\mathrm{aq})+3{\mathrm{e}}^{-}\to \mathrm{Fe}{\mathrm{E}}^{\circ }=-0.04\mathrm{V}$ $\mathrm{N}{\mathrm{i}}^{2+}(\mathrm{aq})+2{\mathrm{e}}^{-}\to \mathrm{Ni}{\mathrm{E}}^{\circ }=-0.25\mathrm{V}$ $\mathrm{A}{\mathrm{g}}^{+}(\mathrm{aq})+{\mathrm{e}}^{-}\to \mathrm{Ag}{\mathrm{E}}^{\circ }=0.80\mathrm{V}$ $\mathrm{A}{\mathrm{u}}^{3+}(\mathrm{aq})+3{\mathrm{e}}^{-}\to \mathrm{Au}{\mathrm{E}}^{\circ }=1.40\mathrm{V}$ Consider the given electrochemical reactions, The number of metal(s) which will be oxidized by $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}$, in aqueous solution is ______.

Match List I with List II $$\begin{array}{llll}& \text{LIST I (Cell)}& & \text{LIST II (Use/Property/Reaction)}\\ \text{A.}& \text{Leclanche cell}& \text{I.}& \text{Converts energy of combustion into electrical energy}\\ \text{B.}& \text{Ni - Cd cell}& \text{II.}& \text{Does not involve any ion in solution and is used in hearing aids}\\ \text{C.}& \text{Fuel cell}& \text{III.}& \text{Rechargeable}\\ \text{D.}& \text{Mercury cell}& \text{IV.}& \text{Reaction at anode}\mathrm{Zn}\to \mathrm{Z}{\mathrm{n}}^{2+}+2{\mathrm{e}}^{-}\end{array}$$ Choose the correct answer from the options given below :

1. A.A-III, B-I, C-IV, D-II
2. B.A-I, B-II, C-III, D-IV
3. C.A-IV, B-III, C-I, D-II
4. D.A-II, B-III, C-IV, D-I

Which out of the following is a correct equation to show change in molar conductivity with respect to concentration for a weak electrolyte, if the symbols carry their usual meaning :

1. A.${\Lambda }_{\mathrm{m}}-{\Lambda }_{\mathrm{m}}^{\circ }+{\mathrm{AC}}^{\frac{1}{2}}=0$
2. B.${\Lambda }_{\mathrm{m}}^2\mathrm{C}+{\mathrm{K}}_{\mathrm{a}}{\Lambda }_{\mathrm{m}}^{\circ 2}-{\mathrm{K}}_{\mathrm{a}}{\Lambda }_{\mathrm{m}}{\Lambda }_{\mathrm{m}}^{\circ }=0$
3. C.${\Lambda }_{\mathrm{m}}-{\Lambda }_{\mathrm{m}}^{\circ }-{\mathrm{AC}}^{\frac{1}{2}}=0$
4. D.${\Lambda }_{\mathrm{m}}^2\mathrm{C}-{\mathrm{K}}_{\mathrm{a}}{\Lambda }_{\mathrm{m}}^{\circ 2}+{\mathrm{K}}_{\mathrm{a}}{\Lambda }_{\mathrm{m}}{\Lambda }_{\mathrm{m}}^{\circ }=0$

The reaction; $$\frac{1}{2}{\mathrm{H}}_{2(\mathrm{g})}+{\mathrm{AgCl}}_{(\mathrm{s})}\to {\mathrm{H}}_{(\mathrm{aq})}^{+}+{\mathrm{Cl}}_{(\mathrm{aq})}^{-}+{\mathrm{Ag}}_{(\mathrm{s})}$$ occurs in which of the following galvanic cell :

1. A.$\mathrm{Pt}\left|{\mathrm{H}}_{2(\mathrm{g})}\right|{\mathrm{HCl}}_{(soln.)}\left|{\mathrm{AgNO}}_{3(\mathrm{aq})}\right|\mathrm{Ag}$
2. B.$\mathrm{Ag}\left|{\mathrm{AgCl}}_{(\mathrm{s})}\right|{\mathrm{KCl}}_{(soln.)}\left|{\mathrm{AgNO}}_{3(\mathrm{aq})}\right|\mathrm{Ag}$
3. C.$\mathrm{Pt}\left|{\mathrm{H}}_{2(\mathrm{g})}\right|{\mathrm{KCl}}_{(soln.)}\left|{\mathrm{AgCl}}_{(\mathrm{s})}\right|\mathrm{Ag}$
4. D.$\mathrm{Pt}\left|{\mathrm{H}}_{2(\mathrm{g})}\right|{\mathrm{HCl}}_{(soln.)}\left|{\mathrm{AgCl}}_{(\mathrm{s})}\right|\mathrm{Ag}$

How can an electrochemical cell be converted into an electrolytic cell ?

1. A.Applying an external opposite potential greater than ${\text{E}}_{\text{cell}}^0$
2. B.Exchanging the electrodes at anode and cathode.
3. C.Applying an external opposite potential lower than ${\text{E}}_{\text{cell}}^0$
4. D.Reversing the flow of ions in salt bridge.

For the electrochemical cell $M|{\mathrm{M}}^{2+}||X|{\mathrm{X}}^{2-}$ If ${\mathrm{E}}_{({\mathrm{M}}^{2+}/M)}^0=0.46\mathrm{V}$ and ${\mathrm{E}}_{(X/{\mathrm{X}}^{2-})}^0=0.34\mathrm{V}$. Which of the following is correct?

1. A.${\mathrm{E}}_{\mathrm{cell}}=0.80\mathrm{V}$
2. B.$\mathrm{M}+\mathrm{X}\to {\mathrm{M}}^{2+}+{\mathrm{X}}^{2-}$ is a spontaneous reaction
3. C.${\mathrm{E}}_{\mathrm{cell}}=-0.80\mathrm{V}$
4. D.${\mathrm{M}}^{2+}+{\mathrm{X}}^{2-}\to \mathrm{M}+\mathrm{X}$ is a spontaneous reaction

Fuel cell, using hydrogen and oxygen as fuels, A. has been used in spaceship B. has an efficiency of 40% to produce electricity C. uses aluminum as catalysts D. is eco-friendly E. is actually a type of Galvanic cell only Choose the correct answer from the options given below:

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

For a strong electrolyte, a plot of molar conductivity against $(\text{concentration}{)}^{1/2}$ is a straight line, with a negative slope, the correct unit for the slope is

1. A.$\text{S}{\text{cm}}^2{\text{ mol}}^{-3/2}\text{ L}$
2. B.$\text{S}{\text{cm}}^2{\text{ mol}}^{-3/2}{\text{ L}}^{-1/2}$
3. C.$\text{S}{\text{cm}}^2{\text{ mol}}^{-1}{\text{ L}}^{1/2}$
4. D.$\text{S}{\text{cm}}^2{\text{ mol}}^{-3/2}{\text{ L}}^{1/2}$

Identify the factor from the following that does not affect electrolytic conductance of a solution.

1. A.The nature of solvent used.
2. B.The nature of the electrolyte added.
3. C.The nature of the electrode used.
4. D.Concentration of the electrolyte.

The metals that are employed in the battery industries are A. $\mathrm{Fe}$ B. $\mathrm{Mn}$ C. $\mathrm{Ni}$ D. $\mathrm{Cr}$ E. $\mathrm{Cd}$ Choose the correct answer from the options given below:

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

Number of alkanes obtained on electrolysis of a mixture of $\mathrm{C}{\mathrm{H}}_3\mathrm{COONa}$ and ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{COONa}$ is ____.

The values of conductivity of some materials at $298.15\mathrm{K}$ in $\mathrm{S}{\mathrm{m}}^{-1}$ are $2.1\times 10^3$, $1.0\times 10^{-16},1.2\times 10,3.91,1.5\times 10^{-2},1\times 10^{-7},1.0\times 10^3$. The number of conductors among the materials is ____.

The mass of zinc produced by the electrolysis of zinc sulphate solution with a steady current of $0.015\text{ A}$ for 15 minutes is _________ $\times 10^{-4}\text{ g}$. (Atomic mass of zinc $=65.4\text{ amu}$)

A constant current was passed through a solution of $\mathrm{AuC}{\mathrm{l}}_4^{-}$ ion between gold electrodes. After a period of 10.0 minutes, the increase in mass of cathode was $1.314\text{ g}$. The total charge passed through the solution is _________ $\times 10^{-2}\text{ F}$. (Given atomic mass of $\mathrm{Au}=197$)

For lead storage battery pick the correct statements A. During charging of battery, $\mathrm{PbS}{\mathrm{O}}_4$ on anode is converted into $\mathrm{Pb}{\mathrm{O}}_2$ B. During charging of battery, $\mathrm{PbS}{\mathrm{O}}_4$ on cathode is converted into $\mathrm{Pb}{\mathrm{O}}_2$ C. Lead storage battery consists of grid of lead packed with $\mathrm{Pb}{\mathrm{O}}_2$ as anode D. Lead storage battery has $\sim 38\%$ solution of sulphuric acid as an electrolyte Choose the correct answer from the options given below:

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

In an electrochemical reaction of lead, at standard temperature, if ${\mathrm{E}}^0\left({\mathrm{Pb}}^{2+}/\mathrm{Pb}\right)=m\text{ Volt}$ and ${\mathrm{E}}^0\left({\mathrm{Pb}}^{4+}/\mathrm{Pb}\right)=n\text{ Volt}$, then the value of ${\mathrm{E}}^0\left({\mathrm{Pb}}^{2+}/{\mathrm{Pb}}^{4+}\right)$ is given by $m-xn$. The value of $x$ is _________. (Nearest integer)

The number of correct statements from the following is _________ A. ${\mathrm{E}}_{\text{cell}}$ is an intensive parameter B. A negative ${\mathrm{E}}^{\ominus }$ means that the redox couple is a stronger reducing agent than the ${\mathrm{H}}^{+}/{\mathrm{H}}_2$ couple. C. The amount of electricity required for oxidation or reduction depends on the stoichiometry of the electrode reaction. D. The amount of chemical reaction which occurs at any electrode during electrolysis by a current is proportional to the quantity of electricity passed through the electrolyte.

The specific conductance of 0.0025 M acetic acid is $5\times 10^{-5}{\text{ S cm}}^{-1}$ at a certain temperature. The dissociation constant of acetic acid is _________ $\times 10^{-7}$ (Nearest integer) Consider limiting molar conductivity of ${\text{CH}}_3\text{COOH}$ as $400{\text{ S cm}}^2{\text{ mol}}^{-1}$