Question

The hydroxide ion concentration of a solution is ${10}^{-6}$ mol/litre. The $pH$ of the solution is:

• A. $8$
• B. $6$
• C. $-8$
• D. $-6$

Answer 1

Answer: (A)

$8$

$\left[O{H}^{-}\right]={10}^{-6}M$.

But $\left[H^{+}\right]\left[O{H}^{-}\right]={10}^{-14}$.

$\left[H^{+}\right]=\frac{{10}^{-14}}{\left[O{H}^{-}\right]}=\frac{{10}^{-14}}{{10}^{-6}}M$.

Hence, $\left[H^{+}\right]={10}^{-8}M$.

$pH=-log\left[H^{+}\right]=-log{10}^{-8}=8$.