JEE Main 2019 — Chemistry Physical Chemistry

2019mcqhard

Consider the following statements

$(a)$ The pH of a mixture containing $400 mL$ of $0.1 M {H}_{2}S{O}_{4}$ and $400 mL$ of $0.1 M NaOH$ will be approximately $1.3.$

$(b)$ Ionic product of water is temperature dependent.

$(c)$ A monobasic acid with ${K}_{a}={10}^{-5}$ has a $pH=5$ . The degree of dissociation of this acid is $50%$ .

$(d)$ The Le Chatelier's principle is not applicable to common-ion effect.

The correct statements are:

Official previous-year question

Held on 10 Apr 2019 · Verified 6 Jul 2026.

Options

A
$(b)$ and $(c)$
B
$(a), (b)$ and $(d)$
C
$(a)$ and $(b)$
D
$(a), (b)$ and $(c)$

Did you get this right?

Solution

Strong acid + Strong base mixture

$n [{H}_{2}S{O}_{4}]>n[NaOH]$ So ${H}^{+}$ will be more

$[{H}^{+}]=\frac{2\times 0.1\times 400-0.1\times 400}{800}=0.05$

$pH=-\mathrm{log}{H}^{+}=-\mathrm{log}0.05=1.3$

(b) The ionic product of water is temperature dependent

${\text{k}}_{a}=\frac{C{\alpha }^{2}}{(1-\alpha )}$

${\text{k}}_{a}=\frac{C\alpha .\alpha }{(1-\alpha )}$

${\text{k}}_{a}=\frac{({H}^{+})\alpha }{1-\alpha }$

${10}^{-5}={10}^{-5}\times \frac{\alpha }{1-\alpha }$

$1-\alpha =\alpha$

$\alpha =\frac{1}{2}=0.5$

(d) Le-Chatelier’s Principle in applicable on Common Ion Effect

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Solution

Strong acid + Strong base mixture

$n [{H}_{2}S{O}_{4}]>n[NaOH]$ So ${H}^{+}$ will be more

$[{H}^{+}]=\frac{2\times 0.1\times 400-0.1\times 400}{800}=0.05$

$pH=-\mathrm{log}{H}^{+}=-\mathrm{log}0.05=1.3$

(b) The ionic product of water is temperature dependent

${\text{k}}_{a}=\frac{C{\alpha }^{2}}{(1-\alpha )}$

${\text{k}}_{a}=\frac{C\alpha .\alpha }{(1-\alpha )}$

${\text{k}}_{a}=\frac{({H}^{+})\alpha }{1-\alpha }$

${10}^{-5}={10}^{-5}\times \frac{\alpha }{1-\alpha }$

$1-\alpha =\alpha$

$\alpha =\frac{1}{2}=0.5$

(d) Le-Chatelier’s Principle in applicable on Common Ion Effect

JEE Main 2019 — Chemistry Physical Chemistry

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JEE Main 2019 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

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More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

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