Question

A solution of Sodium Hydroxide (NaOH) has a pH of 9. What will be the concentration of $O{H}^{-}$ ions?

• A. ${10}^{-9}M$
• B. ${10}^{-6}M$
• C. ${10}^{-4}M$
• D. ${10}^{-5}M$

Answer 1

The correct option is D ${10}^{-5}M$

$WeknowpH+pOH=149+pOH=14\Rightarrow pOH=14-9=5pOH=-lo{g}_{10}\left[O{H}^{-}\right]=5\left[O{H}^{-}\right]={10}^{-5}M$
Hence concentraion of $O{H}^{-}$ is ${10}^{-5}M$