Question

An aqueous solution contains${10}^{-4}\left[H^{+}\right]$. If it is diluted by mixing equal volume of water then the concentration of $O{H}^{-}$ in $mold{m}^{-3}$ will be:

• A. $0.5\times {10}^{-10}$
• B. $2\times {10}^{-10}$
• C. ${10}^{-6}$
• D. ${10}^{-8}$

Answer 1

The correct option is A $0.5\times {10}^{-10}$

$\left[H^{+}\right]={10}^{-4}$

We know, $\left[H^{+}\right]\left[O{H}^{-}\right]=Kw$

$Kw$ only depends on temperature

Value for $Kw$ at ${25}^o$ is ${10}^{-14}$

$\therefore {10}^{-4}\left[O{H}^{-}\right]={10}^{-14}$

$⟹\left[O{H}^{-}\right]={10}^{-10}$

When volume is doubled, concentration becomes half.

$\therefore \left[O{H}^{-}\right]=0.5\times {10}^{-10}$ $mol/d{m}^3$