Q22 / 180 · COMEDK 2023 (Memory Based) · Chemistry

A buffer solution has equal volumes of $0.1 \mathrm{M}$ $\mathrm{NH}_4 \mathrm{OH}$ and $0.01 \mathrm{M} \mathrm{NH}_4 \mathrm{Cl}$. The $\mathrm{pK}$ of the base is 5 . The $\mathrm{pH}$ is

  • Correct answer
    A
    10
  • B
    9
  • C
    4
  • D
    7

Solution

$\mathrm{pOH}=p K_b+\log \frac{[\text { Salt }]}{[\text { Base }]}$ $\begin{aligned} & =5+\log \frac{0.01}{0.01}=5+\log \frac{1}{10}=5+(-1)=4 \\ & \mathrm{pH}=14-\mathrm{pOH}=14-4=10\end{aligned}$

Hence, the correct answer is option: 'A'.

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