MCQ
What is the $pH$  of $0.1\,M\,N{H_3}$
  • A
    $11.27$
  • B
    $11.13$
  • C
    $12$
  • D
    $9.13$

Answer

$NH _3+ H _2 O \rightleftharpoons NH _4+ OH ^{-}$

$Kb =\frac{\left[ NH _4^{+}\right]\left[ OH ^{-}\right]}{\left[ NH _3\right]}$

$1.8 \times 10^{-5}=\frac{ x ^2}{0.1}$

$\Rightarrow x =\sqrt{1.8 \times 10^{-6}}$

$=1.34 \times 10^{-3}$

$\therefore\left[ OH ^{-}\right]\left[ H ^{+}\right]=1.34 \times 10^{-3}\left[ H ^{+}\right]=10^{-14}$

$\Rightarrow pH =11.13$

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