JEE Main 2021 — Chemistry Physical Chemistry

2021mcqmedium

Given below are two statements:

Statement I : The limiting molar conductivity of $\mathrm{KCl}$ (strong electrolyte) is higher compared to that of $\mathrm{CH}_{3} \mathrm{COOH}$ (weak electrolyte).

Statement II : Molar conductivity decreases with decrease in concentration of electrolyte.

In the light of the above statements, choose the most appropriate answer from the options given below:

Official previous-year question

Held on 26 Aug 2021 · Verified 6 Jul 2026.

Options

A
Statement I is false but Statement II is true
B
Both Statement I and Statement II are true
C
Statement I is true but Statement II is false
D
Both Statement I and Statement II are false

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Solution

lon	${K}^{+}$	${\mathrm{Cl}}^{-}$	${\mathrm{CH}}_{3}{\mathrm{COO}}^{-}$	${H}^{+}$
${\lambda }^{\circ }/(S{\mathrm{cm}}^{2}{\mathrm{mol}}^{-1})$	$73.5$	$76.3$	$40.9$	$349.6$

{\lambda }^{\circ }M({\mathrm{CH}}_{3}\mathrm{COOH})={\lambda }^{\circ }M({H}^{+})+{\lambda }^{\circ }M({\mathrm{CH}}_{3}{\mathrm{COO}}^{-})

$=349.6+40.9=390.5{\mathrm{Scm}}^{2}{\mathrm{mol}}^{-1}$

${\lambda }^{\circ }M(\mathrm{KCl})={\lambda }^{\circ }M({K}^{+})+{\lambda }^{\circ }M({\mathrm{Cl}}^{-})$

$=73.5+76.3=149.8{\mathrm{Scm}}^{2}{\mathrm{mol}}^{-1}$

So, statement-I is false.

For an electrolyte the dilution increases (or) decrease in concentration, the number of ions increases due to increase of degree of dissociation. So, the molar conductance increases. Hence, Statement-II is false.

JEE Main 2021 Chemistry, Electrochemistry — solution figure

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Solution

lon	${K}^{+}$	${\mathrm{Cl}}^{-}$	${\mathrm{CH}}_{3}{\mathrm{COO}}^{-}$	${H}^{+}$
${\lambda }^{\circ }/(S{\mathrm{cm}}^{2}{\mathrm{mol}}^{-1})$	$73.5$	$76.3$	$40.9$	$349.6$

{\lambda }^{\circ }M({\mathrm{CH}}_{3}\mathrm{COOH})={\lambda }^{\circ }M({H}^{+})+{\lambda }^{\circ }M({\mathrm{CH}}_{3}{\mathrm{COO}}^{-})

$=349.6+40.9=390.5{\mathrm{Scm}}^{2}{\mathrm{mol}}^{-1}$

${\lambda }^{\circ }M(\mathrm{KCl})={\lambda }^{\circ }M({K}^{+})+{\lambda }^{\circ }M({\mathrm{Cl}}^{-})$

$=73.5+76.3=149.8{\mathrm{Scm}}^{2}{\mathrm{mol}}^{-1}$

So, statement-I is false.

JEE Main 2021 Chemistry, Electrochemistry — solution figure

JEE Main 2021 — Chemistry Physical Chemistry

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JEE Main 2021 — Chemistry Physical Chemistry

Options

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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