Equilibrium Question 305
Question: For a weak acid $ HA $ with dissociation constant $ {10^{-9}},pOH $ of its 0.1 M solution is [CBSE PMT 1989]
Options:
A) 9
B) 3
C) 11
D) 10
Show Answer
Answer:
Correct Answer: D
Solution:
Dissociation constant of $ HA={10^{-9}} $
$ HA $ ⇌ $ {H^{+}}+{A^{-}} $
$ [{H^{+}}]=\sqrt{\frac{K_{a}}{C}} $
$ =\sqrt{\frac{{10^{-9}}}{0.1}} $ ; $ [{H^{+}}]={10^{-4}} $
$ \therefore ,pH=4 $
$ \because ,pH+pOH=14 $
$ pOH=14-pH $
$ =14-4 $ ; $ pOH=10 $
