Which of the following statement(s) is/are correct? (A) The $\mathrm{pH}$ of $1\times {10}^{–8}M\mathrm{HCl}$ solution is $8$. (B) The conjugate base of ${H}_{2}{\mathrm{PO}}^{4-}$ is ${\mathrm{HPO}}_{4}^{2-}$. (C) ${K}_{w}$ increases with increase in temperature. (D) When a solution of a weak monoprotic acid is titrated against a strong base at half neutralisation point, $\mathrm{pH}=\frac{1}{2}{\mathrm{pK}}_{a}$. Choose the correct answer from the options given below:

JEE Main 2023 — Chemistry Physical Chemistry

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Which of the following statement(s) is/are correct?

(A) The $\mathrm{pH}$ of $1\times {10}^{–8}M\mathrm{HCl}$ solution is $8$ .

(B) The conjugate base of ${H}_{2}{\mathrm{PO}}^{4-}$ is ${\mathrm{HPO}}_{4}^{2-}$ .

(D) When a solution of a weak monoprotic acid is titrated against a strong base at half neutralisation point, $\mathrm{pH}=\frac{1}{2}{\mathrm{pK}}_{a}$ . Choose the correct answer from the options given below:

Official previous-year question

Held on 15 Apr 2023 · Verified 6 Jul 2026.

Options

A
$(B),(C)$
B
$(A),(D)$
C
$(A),(B),(C)$
D
$(B),(C),(D)$

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Solution

When concentration of ${H}^{+}$ ion is more than ${10}^{-7}M$ , the proton concentration from water must be considered. Hence, the pH of ${10}^{-8}M\mathrm{HCl}$ solution is not equal to 8.

$\underset{\mathrm{Acid}}{{H}_{2}{\mathrm{PO}}_{4}^{-}}\overset{}{\rightleftharpoons }\underset{\mathrm{Conjugate}\mathrm{base}}{{\mathrm{HPO}}_{4}^{2-}}+{H}^{+}$

${K}_{w}$ increase with increase in temperature as dissociation of water increases with increase in temperature.

When weak monoprotic acid is titrated against strong base, at half neutralization point, the solution becomes acidic buffer and its $\mathrm{pH}$ is given by

$\mathrm{pH}={\mathrm{pK}}_{a}+\mathrm{log}\frac{[\mathrm{Salt}]}{[\mathrm{Acid}]}$

$\Rightarrow \mathrm{pH}={\mathrm{pK}}_{a}+0$ as $[\mathrm{salt}]=[\mathrm{acid}]$

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Solution

When concentration of ${H}^{+}$ ion is more than ${10}^{-7}M$ , the proton concentration from water must be considered. Hence, the pH of ${10}^{-8}M\mathrm{HCl}$ solution is not equal to 8.

$\underset{\mathrm{Acid}}{{H}_{2}{\mathrm{PO}}_{4}^{-}}\overset{}{\rightleftharpoons }\underset{\mathrm{Conjugate}\mathrm{base}}{{\mathrm{HPO}}_{4}^{2-}}+{H}^{+}$

${K}_{w}$ increase with increase in temperature as dissociation of water increases with increase in temperature.

When weak monoprotic acid is titrated against strong base, at half neutralization point, the solution becomes acidic buffer and its $\mathrm{pH}$ is given by

$\mathrm{pH}={\mathrm{pK}}_{a}+\mathrm{log}\frac{[\mathrm{Salt}]}{[\mathrm{Acid}]}$

$\Rightarrow \mathrm{pH}={\mathrm{pK}}_{a}+0$ as $[\mathrm{salt}]=[\mathrm{acid}]$

JEE Main 2023 — Chemistry Physical Chemistry

Options

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Solution

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JEE Main 2023 — 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

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