Electrochemistry - JEE Main Previous Year Questions with Solutions

JEE Main Previous Year Papers Questions of Chemistry with Solutions are available at eSaral. Practicing JEE Main chapter wise questions of Chemistry will help the JEE aspirants in realizing the question pattern as well as help in analyzing weak & strong areas.

Simulator

Previous Years AIEEE/JEE Mains Questions

Q. Given :

$\mathrm{E}_{\mathrm{Fe}^{-3} / \mathrm{Fe}}^{\circ}=-0.036 \mathrm{V}, \quad \mathrm{E}_{\mathrm{Fe}^{-2} / \mathrm{Fe}}^{\circ}=-0.439 \mathrm{V}$. The value of standard electrode potential for the change.

$\mathrm{Fe}^{+3}_{(\mathrm{aq})}+\mathrm{e}^{-} \longrightarrow \mathrm{Fe}^{+2}_{(\mathrm{aq})}$ will be :-

(1) 0.770 V (2) –0.27 V (3) –0.072 V (4) 0.385 V

AIEEE 2009

Sol. (1)

$\mathrm{E}^{\circ}=\frac{3 \times-0.036+2 \times 0.439}{1}=0.77 \Rightarrow \mathrm{A}$

Q. The Gibbs energy for the decomposition of $\mathrm{Al}_{2} \mathrm{O}_{3}$ at $500^{\circ} \mathrm{C}$ is as follows :

$\frac{2}{3} \mathrm{Al}_{2} \mathrm{O}_{3} \longrightarrow \frac{4}{3} \mathrm{Al}+\mathrm{O}_{2}, \mathrm{AG}=+966 \mathrm{KJ} \mathrm{mol}^{-1}$ The potential difference needed for electrolytic reduction of $\mathrm{Al}_{2} \mathrm{O}_{3}$ at $500^{\circ} \mathrm{C}$ is at least :-

(1) 5.0 V (2) 4.5 V (3) 3.0 V (4) 2.5 V

AIEEE 2010

Sol. (4)

$966 \times 10^{3}=4 \times 96500 \times \mathrm{E} \Rightarrow \mathrm{E}=2.5 \mathrm{V}$

Q. Resistance of 0.2 M solution of an electrolyte is $50 \Omega$. The specific conductance of the solution is 1.3 S $\mathrm{m}^{-1}$. If resistance of the 0.4M solution of the same electrolyte is $260 \Omega$, its molar conductivity is :-

(1) $6250 \mathrm{Sm}^{2} \mathrm{mol}^{-1}$

(2) $6.25 \times 10^{-4} \mathrm{S} \mathrm{m}^{2} \mathrm{mol}^{-1}$

(3) $625 \times 10^{-4} \mathrm{S} \mathrm{m}^{2} \mathrm{mol}^{-1}$

(4) $62.5 \mathrm{S} \mathrm{m}^{2} \mathrm{mol}^{-1}$

AIEEE 2011/JEE-MAIN 2014

Sol. (2)

Q. The reduction potential of hydrogen half-cell will be negative if :-

(1) $\mathrm{p}\left(\mathrm{H}_{2}\right)=2 \operatorname{atm}\left[\mathrm{H}^{+}\right]=1.0 \mathrm{M}$

(2) $\mathrm{p}\left(\mathrm{H}_{2}\right)=2$ atm and $\left[\mathrm{H}^{+}\right]=2.0 \mathrm{M}$

(3) $\mathrm{p}\left(\mathrm{H}_{2}\right)=1$ atm and $\left[\mathrm{H}^{+}\right]=2.0 \mathrm{M}$

(4) $\mathrm{p}\left(\mathrm{H}_{2}\right)=1$ atm and $\left[\mathrm{H}^{+}\right]=1.0 \mathrm{M}$

AIEEE 2011

Sol. (1)

Q. The standard reduction potentials for $\mathrm{Zn}^{2+} / \mathrm{Zn}, \mathrm{Ni}^{2+} / \mathrm{Ni}$ and $\mathrm{Fe}^{2+} / \mathrm{Fe}$ are $-0.76,-0.23$ and – 0.44 V respectively. The reaction $\mathrm{X}+\mathrm{Y}^{+2} \rightarrow \mathrm{X}^{2+}+\mathrm{Y}$ will be spontaneous when

(1) X = Zn, Y = Ni

(2) X = Ni, Y = Fe

(3) X = Ni, Y = Zn

(4) X = Fe, Y = Zn

Sol. (1)

For spontaneous reaction $\mathrm{E}^{\circ}>0 \mathrm{so}(\mathrm{A})$

Q. Given :

Based on the data given above, strongest oxidising agent will be :

(1) Cl–

(2) $\mathrm{Cr}^{3+}$

(3) $\mathrm{Mn}^{2+}$

(4) $\mathrm{MnO}_{4}^{-}$

JEE-Mains 2013

Sol. (4)

Higher the SRP, stronger will be oxidising agent

Hence, $\mathrm{MnO}_{4}^{-}$ is stronger oxidising agent.

Q. The equivalent conductance of NaCl at concentration C and at infinite dilution are $\lambda_{\mathrm{C}}$ and $\lambda_{\infty}$ , respectively. The correct relationship between $\lambda_{\mathrm{C}}$ and $\lambda_{\infty}$ is given as:

(1) $\lambda_{\mathrm{C}}=\lambda_{\infty}-(\mathrm{B}) \sqrt{\mathrm{C}}$

(2) $\lambda_{\mathrm{C}}=\lambda_{\infty}+(\mathrm{B}) \sqrt{\mathrm{C}}$

(3) $\lambda_{\mathrm{C}}=\lambda_{\infty}+(\mathrm{B}) \mathrm{C}$

(4) $\lambda_{\mathrm{C}}=\lambda_{\infty}-(\mathrm{B}) \mathrm{C}$

JEE-Mains 2014

Sol. (1)

Fact

Q. At 298 K, the standard reduction potentials are 1.51 V for $\mathrm{MnO}_{4}-| \mathrm{Mn}^{2+}$ , 1.36 V for $\mathrm{Cl}_{2} | \mathrm{Cl}^{-}$, 1.07 V for $\mathrm{Br}_{2} | \mathrm{Br}^{-},$ and $0.54 \mathrm{V}$ for $\mathrm{I}_{2} | \mathrm{I}^{-} .$ At $\mathrm{pH}=3$, permanganate is expected to oxidize $\left(\frac{\mathrm{RT}}{\mathrm{F}}=0.059 \mathrm{V}\right):-$

(1) $\mathrm{Cl}^{-}$ and $\mathrm{Br}^{-}$

(2) $\mathrm{Cl}^{-}, \mathrm{Br}^{-}$ and $\mathrm{I}^{-}$

(3) $\mathrm{Br}^{-}$ and $\mathrm{I}^{-}$

(4) I- only

JEE-Mains (online) 2015

Sol. (3)

Q. A variable, opposite external potential $\left(\mathrm{E}_{\mathrm{ext}}\right)$ is applied to the cell

$\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1 \mathrm{M}) \| \mathrm{Cu}^{2+}(1 \mathrm{M})\right| \mathrm{Cu}$, of potential 1.1 V. When $\mathrm{E}_{\mathrm{ext}}<1.1 \mathrm{V}$ and $\mathrm{E}_{\mathrm{ext}}>1.1 \mathrm{V}$ , respectively electrons flow from :

(1) anode to cathode in both cases

(2) anode to cathode and cathode to anode

(3) cathode to anode in both cases

(4) cathode to anode and anode to cathode

JEE-Mains (online) 2015

Sol. (2)

Fact

Q. Two Faraday of electricity is passed through a solution of $\mathrm{CuSO}_{4}$. The mass of copper deposited at the cathode is :

(at. mass of Cu = 63.5 amu)

(1) 2g (2) 127 g (3) 0 g (4) 63.5 g

JEE-Mains 2015

Sol. (4)

$2 \mathrm{F}=2 \mathrm{eq}=1$ mole $=63.5 \mathrm{gm}$

Q. Galvanization is applying a coating of :-

(1)Zn (2) Pb (3) Cr (4) Cu

JEE-Mains 2016

Sol. (1)

Galvanization is the process of applying a protective zinc coating of steel or iron, to prevent rusting.

Q. Given

(1)Cr

(2) $\mathrm{Mn}^{2+}$

(3) $\mathrm{Cr}^{3+}$

(4) $\mathrm{Cl}^{-}$

JEE-Mains 2017

Sol. (1)

Since $\mathrm{Cr}^{+3}$ is having least reducing potential, so Cr is the best Reducing agent.

Q. How long (approximate) should water be electrolysed by passing through 100

amperes current so that the oxygen released can completely burn 27.66 g of diborane ?

(Atomic weight of B = 10.8 u)

(1)0.8 hours

(2) 3.2 hours

(3) 1.6 hours

(4) 6.4 hours

JEE-Mains 2018

Sol. (2)

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