1. Tardigrade
  2. Question
  3. Chemistry
  4. A buffer solution is prepared in which the concentration of NH 3 is 0.30 M and the concentration of NH 4+is 0.20 M. If the equilibrium constant, K b for NH 3 equals 1.8 × 10-5, what is the p H of the solution?

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Q. A buffer solution is prepared in which the concentration of $NH _3$ is $0.30 M$ and the concentration of $NH _4^{+}$is $0.20 M$. If the equilibrium constant, $K _b$ for $NH _3$ equals $1.8 \times 10^{-5}$, what is the $p H$ of the solution?

MHT CETMHT CET 2021

Solution:

Given, $K_b=1.8 \times 10^{-5} $
$p K_b=-\log K_b $
$=-\log 1.8 \times 10^{-5}=4.74$
$p O H=p K_b+\log \frac{[\text { salt }]}{[\text { base }]}$
$=4.74+\log \frac{0.20}{0.30}$
$=4.74-0.176=4.56 \\ p H+p O H=14$
$p H=14-4.56=9.44$