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)
Show Answer
Answer:
Correct Answer: 61. $(11.5)$
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 $
BETA
