JEE Main 2019 — Chemistry Physical Chemistry

2019mcqhard

The standard electrode potential ${E}^{o}$ and its temperature coefficient $(\frac{\mathrm{dE}}{\mathrm{dT}})$ for a cell are $2V$ and $-5{\times 10}^{-4} V{K}^{-1}$ at $300 K$ , respectively. The reaction is $\mathrm{Zn}(s)+{\mathrm{Cu}}^{2+}(\mathrm{aq})\rightarrow {\mathrm{Zn}}^{2+}(\mathrm{aq})+\mathrm{Cu}(s)$ . The standard reaction enthalpy $({\Delta }_{r}{H}^{-})$ at $300K$ in $mo{l}^{-1}$ is

$[$ Use $R=8J{K}^{-1}{\mathrm{mol}}^{-1}$ and $F=96,500C{\mathrm{mol}}^{-1}]$

Official previous-year question

Held on 12 Jan 2019 · Verified 6 Jul 2026.

Options

A
$-412.8$
B
$206.4$
C
$-384.0$
D
$192.0$

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Solution

$\Delta \text{G}=-{\mathrm{nFE}}_{\mathrm{cell}} =-2\times 96500\times 2 =-386 \mathrm{kJ}$

$\Delta \text{S}=\mathrm{nF}\frac{\mathrm{dE}}{\mathrm{dT}} =2\times 96500\times -5\times {10}^{-4}J\mathrm{degree}{\mathrm{celcious}}^{-1}$

$=-96.5J$

At $298 K$ ,

$T\Delta \text{S}=298\times (-96.5J) =-28.757 \mathrm{kJ}$

At constant temperature $(T=248K)$ and pressure,

$\Delta G=\Delta H-T\Delta \text{S}$

$\Delta H=\Delta G+T\Delta \text{S}$

$=-386-28.757 =-414.75\simeq -412.8$

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Solution

$\Delta \text{G}=-{\mathrm{nFE}}_{\mathrm{cell}} =-2\times 96500\times 2 =-386 \mathrm{kJ}$

$\Delta \text{S}=\mathrm{nF}\frac{\mathrm{dE}}{\mathrm{dT}} =2\times 96500\times -5\times {10}^{-4}J\mathrm{degree}{\mathrm{celcious}}^{-1}$

$=-96.5J$

At $298 K$ ,

$T\Delta \text{S}=298\times (-96.5J) =-28.757 \mathrm{kJ}$

At constant temperature $(T=248K)$ and pressure,

$\Delta G=\Delta H-T\Delta \text{S}$

$\Delta H=\Delta G+T\Delta \text{S}$

$=-386-28.757 =-414.75\simeq -412.8$

JEE Main 2019 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2019 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry