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JEE MAIN 2025
07.04.25 S2
Question
One litre buffer solution was prepared by adding 0.10 mol each of and in deionised water. The change in pH on addition of 0.05 mol of HCl to the above solution is _____ . (Nearest integer)
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Solution
$\begin{aligned} & \mathrm{pOH}=\mathrm{pK}_{\mathrm{b}}+\log \frac{\left[\mathrm{NH}_4^{+}\right]}{\left[\mathrm{NH}_3\right]} \\ & \mathrm{pOH}=4.745 \\ & \text { on adding } 0.05 \mathrm{moleHCl} \\ & \mathrm{NH}_3+\mathrm{H}^{\oplus} \rightarrow \mathrm{NH}_4^{\oplus} \\ & 0.1 \\ & 0.05 \quad 0.05 \quad 0.1 \\ & \mathrm{pOH}=4.745+\log 3 \\ & \mathrm{pOH}-\mathrm{pOH}=0.477 \\ & 14-\mathrm{pH}-14+\mathrm{pH}=0.477 \\ & \Delta \mathrm{pH}=0.477 \\ & =47.7 \times 10^{-2} \approx 48 \times 10^{-2}\end{aligned}$
Question Tags
JEE Main
Chemistry
Medium
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