JEE Main 2024 — Chemistry Physical Chemistry

2024integerhard

${K}_{a}$ for ${\mathrm{CH}}_{3}\mathrm{COOH}$ is $1.8\times {10}^{-5}$ and ${K}_{b}$ for ${\mathrm{NH}}_{4}\mathrm{OH}$ is $1.8\times {10}^{-5}.$ The $\mathrm{pH}$ of ammonium acetate solution will be

Official previous-year question

Held on 1 Feb 2024 · Verified 6 Jul 2026.

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Solution

${K}_{a}$ of ${\mathrm{CH}}_{3}\mathrm{COOH}$ $=1.8\times {10}^{-5}$

${K}_{a}$ of ${\mathrm{NH}}_{4}\mathrm{OH}$ $=1.8\times {10}^{-5}$

We know that $\mathrm{pH}$ of solution of the salt made up of weak acid $({\mathrm{CH}}_{3}\mathrm{COOH})$ and weak base $({\mathrm{NH}}_{4}\mathrm{OH})$ can be found using formula

$\mathrm{pH}=7+\frac{1}{2}[{\mathrm{pK}}_{a}-{\mathrm{pK}}_{b}]$

${\mathrm{pK}}_{a}=-\mathrm{log}({K}_{a})$

$=-\mathrm{log}(1.8\times {10}^{-5}) =-[\mathrm{log}1.8+\mathrm{log}{10}^{-5}] =-[0.2553-5] =+4.7447 {\mathrm{pK}}_{b}=-\mathrm{log}({K}_{b}) =-\mathrm{log}(1.8\times {10}^{-5}) =4.7447 \mathrm{pH}=7+\frac{1}{2}[4.7447-4.7447] =7+0 =7$

If ${K}_{a}={K}_{b}$ , then $\mathrm{pH}$ of salt is always $7$ .

Therefore, the $\mathrm{pH}$ of given solution is $7$ .

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JEE Main 2024 — Chemistry Physical Chemistry

2024integerhard

Official previous-year question

Held on 1 Feb 2024 · Verified 6 Jul 2026.

Did you get this right?

Solution

${K}_{a}$ of ${\mathrm{CH}}_{3}\mathrm{COOH}$ $=1.8\times {10}^{-5}$

${K}_{a}$ of ${\mathrm{NH}}_{4}\mathrm{OH}$ $=1.8\times {10}^{-5}$

We know that $\mathrm{pH}$ of solution of the salt made up of weak acid $({\mathrm{CH}}_{3}\mathrm{COOH})$ and weak base $({\mathrm{NH}}_{4}\mathrm{OH})$ can be found using formula

$\mathrm{pH}=7+\frac{1}{2}[{\mathrm{pK}}_{a}-{\mathrm{pK}}_{b}]$

${\mathrm{pK}}_{a}=-\mathrm{log}({K}_{a})$

If ${K}_{a}={K}_{b}$ , then $\mathrm{pH}$ of salt is always $7$ .

Therefore, the $\mathrm{pH}$ of given solution is $7$ .

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

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

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JEE Main 2024 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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Organic Chemistry

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JEE Main 2024 — Chemistry Physical Chemistry

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