Question

The hydrogen ion concentration of a $ {{10}^{-8}}M\,HCl $ aqueous solution at 298 K $ ({{K}_{w}}={{10}^{-14}}) $

• A. $ 1.0\times {{10}^{-6}}M $
• B. $ 1.0525\times {{10}^{-7}}M $
• C. $ 9.525\times {{10}^{-8}}M $
• D. $ 1.0\times {{10}^{-8}}M $

Answer 1

Answer: (B)

In aqueous solution of
$ {{10}^{-8}}M\,HCl,[{{H}^{+}}] $ is based upon the concentration of
$ {{H}^{+}} $ ion of $ {{10}^{-8}}M\,HCl $
and concentration of $ {{H}^{+}} $ ion of water
$ {{K}_{w}} $ of $ {{H}_{2}}O={{10}^{-14}}[{{H}^{+}}][O{{H}^{-}}] $
or $ [{{H}^{+}}]={{10}^{-7}}M $ (due to its neutral behaviour)
So, in aqueous solution of $ {{10}^{-8}}M\text{ }HCl, $
$ [{{H}^{+}}]=[{{H}^{+}}] $ of $ HCl+[{{H}^{+}}] $ of water
$ ={{10}^{-8}}+{{10}^{-7}}=11\times {{10}^{-8}}M $
$ \approx 1.10\times {{10}^{-7}}M $
Hence, answer is nearer to [b].