JEE Main 2019 — Chemistry Physical Chemistry

2019mcqhard

${\wedge }_{m}^{o}$ for $\mathrm{NaCl}, \mathrm{HCl}$ and $\mathrm{NaA}$ are $126.4, 425.9$ and $100.5 S {\mathrm{cm}}^{2}{\mathrm{mol}}^{-1}$ respectively. If the conductivity of $0.001 M \mathrm{HA}$ is $5\times {10}^{-5}S {\mathrm{cm}}^{-1}$ , degree of dissociation of $\mathrm{HA}$ is

Official previous-year question

Held on 12 Jan 2019 · Verified 6 Jul 2026.

Options

A
$0.125$
B
$0.75$
C
$0.25$
D
$0.50$

Did you get this right?

Solution

Kohlrausch's law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations.

${\lambda }_{m}^{o}(\mathrm{HA})={\lambda }_{m}^{o}(\mathrm{HCl})+{\lambda }_{m}^{o}(\mathrm{NaA})-{\lambda }^{o}(\mathrm{NaCl})$

$=425.9+100.5-126.4$

$=400$

${\lambda }_{m}^{o}=\frac{K\times 1000}{M}=\frac{5\times {10}^{-5}\times {10}^{3}}{{10}^{-3}}=50$

$\alpha =\frac{50}{400}=0.125$

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JEE Main 2019 — Chemistry Physical Chemistry

2019mcqhard

Official previous-year question

Held on 12 Jan 2019 · Verified 6 Jul 2026.

Options

A
$0.125$
B
$0.75$
C
$0.25$
D
$0.50$

Did you get this right?

Solution

Kohlrausch's law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations.

${\lambda }_{m}^{o}(\mathrm{HA})={\lambda }_{m}^{o}(\mathrm{HCl})+{\lambda }_{m}^{o}(\mathrm{NaA})-{\lambda }^{o}(\mathrm{NaCl})$

$=425.9+100.5-126.4$

$=400$

${\lambda }_{m}^{o}=\frac{K\times 1000}{M}=\frac{5\times {10}^{-5}\times {10}^{3}}{{10}^{-3}}=50$

$\alpha =\frac{50}{400}=0.125$

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

Work through every JEE Main Physical Chemistry PYQ, year by year.

Browse all Chemistry topics

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

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Keep practicing Physical Chemistry

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