Equilibrium Question 394
Question: The dissociation constant of an acid HA is $ 1\times {10^{-5}} $ . The $ pH $ of 0.1 molar solution of the acid will be [KCET (Engg./Med.) 1999]
Options:
A) Five
B) Four
C) Three
D) One
Show Answer
Answer:
Correct Answer: C
Solution:
$ HA $ ⇌ $ {H^{+}}+{A^{-}} $
$ [{H^{+}}]=0.1M $ ; $ {{[{H^{+}}]}^{2}}=K_{a}\times C $
$ [{H^{+}}]=\sqrt{K_{a}\times C}=\sqrt{1\times {10^{-5}}\times 0.1}=\sqrt{{10^{-6}}} $
$ [{H^{+}}]={10^{-3}}M;pH=3 $
