JEE Main 2026 — Chemistry Physical Chemistry

2026integermedium

The pH of a solution obtained by mixing $5$ mL of $0.1$ M $NH_4OH$ solution with $250$ mL of $0.1$ M $NH_4Cl$ solution is _____ $\times 10^{-2}$ . (Nearest integer)

Given: $pK_b(NH_4OH) = 4.74$

$\log 2 = 0.30$

$\log 3 = 0.48$

$\log 5 = 0.70$

Official previous-year question

Held on 4 Apr 2026 · Verified 6 Jul 2026.

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Solution

The given mixture forms a basic buffer solution.

Millimoles of base $NH_4OH = 5 \times 0.1 = 0.5$ mmol

Millimoles of salt $NH_4Cl = 250 \times 0.1 = 25$ mmol

Using the Henderson-Hasselbalch equation for a basic buffer:

$pOH = pK_b + \log \left( \dfrac{[\text{Salt}]}{[\text{Base}]} \right)$

$pOH = 4.74 + \log \left( \dfrac{25}{0.5} \right)$

$pOH = 4.74 + \log (50)$

We know that $\log (50) = \log (5 \times 10) = \log 5 + \log 10 = 0.70 + 1 = 1.70$

$pOH = 4.74 + 1.70 = 6.44$

The pH of the solution is given by:

$pH = 14 - pOH$

$pH = 14 - 6.44 = 7.56$

$pH = 756 \times 10^{-2}$

Answer: $756$

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JEE Main 2026 — Chemistry Physical Chemistry

2026integermedium

The pH of a solution obtained by mixing $5$ mL of $0.1$ M $NH_4OH$ solution with $250$ mL of $0.1$ M $NH_4Cl$ solution is _____ $\times 10^{-2}$ . (Nearest integer)

Given: $pK_b(NH_4OH) = 4.74$

$\log 2 = 0.30$

$\log 3 = 0.48$

$\log 5 = 0.70$

Official previous-year question

Held on 4 Apr 2026 · Verified 6 Jul 2026.

Did you get this right?

Solution

The given mixture forms a basic buffer solution.

Millimoles of base $NH_4OH = 5 \times 0.1 = 0.5$ mmol

Millimoles of salt $NH_4Cl = 250 \times 0.1 = 25$ mmol

Using the Henderson-Hasselbalch equation for a basic buffer:

$pOH = pK_b + \log \left( \dfrac{[\text{Salt}]}{[\text{Base}]} \right)$

$pOH = 4.74 + \log \left( \dfrac{25}{0.5} \right)$

$pOH = 4.74 + \log (50)$

We know that $\log (50) = \log (5 \times 10) = \log 5 + \log 10 = 0.70 + 1 = 1.70$

$pOH = 4.74 + 1.70 = 6.44$

The pH of the solution is given by:

$pH = 14 - pOH$

$pH = 14 - 6.44 = 7.56$

$pH = 756 \times 10^{-2}$

Answer: $756$

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 2026 — Chemistry Physical Chemistry

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Solution

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JEE Main Physical Chemistry in other years

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JEE Main 2026 — 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