Question

A certain weak acid has a dissociation constant of $1.0 \times 10^{ - 4 }$. The equilibrium constant for its reaction with a strong base is

• A. $ 1.0 \times 10^{ - 4} $
• B. $ 1.0 \times 10^{ - 10} $
• C. $ 1.0 \times 10^{ 10} $
• D. $ 1.0 \times 10^{ 14} $

Answer 1

Answer: (C)

The reaction of HA with strong base is
$ HA + OH^- \rightleftharpoons H_2O + A^-$
K = $ \frac{ [ A^- ]}{ [ HA ] \, [ OH^-] } \times \frac{ [ H^+ ]}{ [ H^+ ] } = \frac{ K_a }{ K_w } $
= $ \frac{ 10^{ - 4 }}{ 10^{ - 14 }} = 10^{ 10} $