pH of a buffer solution containing $\mathrm{NH}_{4} \mathrm{Cl}$ and $\mathrm{NH}_{4} \mathrm{OH}$ i

Question

pH of a buffer solution containing $\mathrm{NH}_{4} \mathrm{Cl}$ and $\mathrm{NH}_{4} \mathrm{OH}$ in which concentration of the salt is double the concentration of the base, is 8.98 . pKb for $\mathrm{NH}_{4} \mathrm{OH}$ is\

Professor PC Thomas Classes · Answer

This is a basic buffer\ $	herefore \mathrm{pOH}=\mathrm{pKb}+\log \frac{[	ext { salt }]}{[	ext { base }]}$\ $\mathrm{pH}=8.98, \mathrm{pOH}=14-8.98=5.02$\ $	herefore 5.02=\mathrm{pKb}+\log 2$\ $	herefore \mathrm{pKb}=5.02-0.3010 \approx 4.72$\