The Ph OF NEUTRAL WATER AT `25^(@)C` is `7.0.` As the temperature increases, ionisation of water increases, however the concentration of `H^(+)` ions nad `OH^(-)` ions equal. What will be the ph of puire water at `60^(@)C`?

Options

A. Equal to `7.0`
B. Greater than `7.0`
C. Less than `7.0`
D. Equal to zero

Answer

C

Explanation

The pH of neutral water of `25^(@)C ` is 7.0
At `25^(@)C [H^(+)] = [OH^(-)] = 10^(-7)`
and `K_(w) = [H^(+)] [OH^(-)] = 10^(-14)`
On heating , `K_(w) ` increases , i.e., `[H^(+)][OH^(-)] gt 10^(-14)`
As `[H^(+)] = [OH^(-)] or , [H^(+)]^(2) ge 10^(-14)`
or , `[H^(+)] gt 10^(-7)` M
` :. pH lt 7 ` With rise in temperature, pH of pure water decreases and it become less than 7 at `60^(@)C ` .