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 $



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