Question

The hydrogen ion concentration of a 10${}^{-8}$ M $HCl$ aqueous solution at 298 K is:

[Given that: $K_w$ = 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

The correct option is B $1.0525\times {10}^{-7}$ M

$HCl\to H^{+}+C{l}^{-}$
${10}^{-8}\times {10}^{-8}$
$K_w=\left[H^{+}\right]\left[O{H}^{-}\right]$
${10}^{-14}=({10}^{-8}+a)\times a$
$a=0.95\times {10}^{-7}\left[H^{+}\right]$
$={10}^{-8}+(0.95\times {10}^{-7})$

$=1.05\times {10}^{-7}M$.

Hence option B is correct.