Question

For water at ${25}^{o}C$, $2\times {10}^{-7}$ moles per litre is the correct answer for which one of the following?

• A. $\left[H^{+}\right]+\left[O{H}^{-}\right]$
• B. $[H^{+}{]}^2$
• C. $[O{H}^{-}{]}^2$
• D. $\left[H^{+}\right]-\left[O{H}^{-}\right]$

Answer 1

The correct option is A $\left[H^{+}\right]+\left[O{H}^{-}\right]$

At ${25}^{o}C$, For pure water

Concentration of $\left[H^{+}\right]={10}^{-7}$ moles per litre

Concentration of ${[}^{-}OH]={10}^{-7}$ moles per litre

as $pH=pOH=7$

Thus $\left[H^{+}\right]+{[}^{-}OH]={10}^{-7}+{10}^{-7}=2\times {10}^{-7}moles/L$