Question

$pH$ of an aqueous $1\times {10}^{-8}MNaOH$ solution is __________.

• A. $8$
• B. $7.04$
• C. $7$
• D. $6$

Answer 1

The correct option is B $7.04$

$H_{2}O\to H^{+}+O{H}^{-}$

$\left[H^{+}\right]=\left[O{H}^{-}\right]$

$Kw=\left[H^{+}\right]\times \left[O{H}^{-}\right]=1.0\times {10}^{-14}$

$NaOH$ is a strong base

$NaOH=N{a}^{+}+O{H}^{-}$

$OH-=1\times {10}^{-8}M$

Total concentration $O{H}^{-}\approx 1.0\times {10}^{-7}+1\times {10}^{-8}\approx 1.1\times {10}^{-7}M$

$pOH=6.96$

$pH=14-6.96=7.04$