Chemical and Ionic Equilibrium - Result Question 117
####61. What is the $pH$ of a $0.50 M$ aqueous $NaCN$ solution?
( $p K _b$ of $CN^{-}=4.70$ ).
(1996, 2M)
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Solution:
- $CN^{-}+H _2 O \rightleftharpoons HCN+OH^{-}$
$$ K _h=2 \times 10^{-5} $$
$$ \left[OH^{-}\right]=\sqrt{K _h C}=\sqrt{2 \times 10^{-5} \times 0.5}=\sqrt{10^{-5}} $$
$$ pOH=2.5 \text { and } pH=11.5 $$
