A buffer solution is prepared by mixing $0.2 \mathrm{M} \mathrm{NH} \mathrm{O}_4 \mathrm{OH}$ and $1…

A buffer solution is prepared by mixing $0.2 \mathrm{M} \mathrm{NH} \mathrm{O}_4 \mathrm{OH}$ and $1 \mathrm{M} \mathrm{NH}_4 \mathrm{Cl}$. What is the pH value of buffer solution? (Give $\mathrm{pK}_{\mathrm{b}}=7.744$ )
  1. 5.56
  2. 6.99
  3. 8.44
  4. 9.56

Solution

For a basic buffer solution, $\begin{aligned} \mathrm{pOH} & =\mathrm{pK}_{\mathrm{b}}+\log _{10} \frac{[\text { Salt }]}{[\text { Base }]} \\ & =7.744+\log _{10} \frac{1}{0.2} \\ & =7.744+0.698 \\ \therefore \quad \mathrm{pOH} & =8.44 \\ \therefore \quad \mathrm{Now} & , \mathrm{pH}+\mathrm{pOH}=14 \\ \therefore \quad \mathrm{pH} & =14-\mathrm{pOH}=14-8.44=5.56 \end{aligned}$

Asked in: MHT CET 2024 (15 May Shift 1)

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