Question

pH of the solution is 4. The hydroxide ion concentration of the solution would be ____.

• A. ${10}^{-4}$
• B. ${10}^{-10}$
• C. ${10}^{-2}$
• D. ${10}^{-12}$

Answer 1

The correct option is B ${10}^{-10}$

$pH=-log[H{]}^{+}=4$.
Hence, $[H{]}^{+}={10}^{-4}$ M.
But $\left[H{]}^{+}\right[OH{]}^{-}={10}^{-14}$.
Hence, ${10}^{-4}\times [OH{]}^{-}={10}^{-14}$.
$[OH{]}^{-}={10}^{-10}$.