Question

What is the hydroxide concentration for a solution with a $pH$ of 10 at 25${}^o$C?

• A. ${10}^{-14}M$
• B. ${10}^{-10}M$
• C. ${10}^{-7}M$
• D. ${10}^{-4}M$
• E. ${10}^{-1}M$

Answer 1

The correct option is D ${10}^{-4}M$

We know that, $pH$ $+$ $pOH$ $=$ $14$.

In the question given, $pH$ $=$ $10$, hence, $pOH$ $=$ $14$$-$$10$=$4$.

We also know the formula, $pOH$ $=$ $-log$$\left[O{H}^{-}\right]$

where, $\left[O{H}^{-}\right]$ is the concentration of $O{H}^{-}$.

Putting the value of $pOH$ in the above mentioned equation, we have, $4$ $=$ $-log$$\left[O{H}^{-}\right]$

Thus, $\left[O{H}^{-}\right]$ comes out to be equal to ${10}^{-4}$$M$

Option D is the correct answer.