Question

The hydrogen ion concentration of a ${10}^{-8}MHCl$ 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
${10}^{-8}MHCl,[H^{+}]$ is based upon the concentration of
$H^{+}$ ion of ${10}^{-8}MHCl$
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 ${10}^{-8}MHCl,$
$[H^{+}]=[H^{+}]$ 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].