Will the pH of water be same at `4^(@)C` and `25^(@)C` ? Explain.

Explanation

At `25^(@)C, K_(w)for H_(2)O=1.0xx10^(-14)`
Thus `[H^(+)]=[OH^(-)]=10^(-7)`
or `pH=7`
`K_(w)` of water decreases with decreases in temparature because `H_(2)O hArr H^(+)+OH^(-)` is endothermic change (follow Le Chatelier's principle).The low dissociation of `H_(2)O` will lead for lower concentrations of `H^(+)` and `OH^(-)`. Thus pH of water will be more than 7 at `4^(@)C`. `(K_(w)lt10^(-14)at 4^(@)C)`