The $pH$ of pure water or neutral solution at $50\,^{\circ}C$ is .... ($pK_w = 13.26$ at $50\,^{\circ}C$)

For the following Assertion and Reason,the correct option is
Assertion : The $pH$ of water increases with increase in temperature.
Reason : The dissociation of water into $H^{+}$ and $OH^{-}$ is an exothermic reaction.

The number of $OH^{-}$ ions in $1 \ mL$ of solution having $pH = 4$ is :-

Derive the relation between $pH$ and $pOH$.

The concentration of hydronium $({H_3}{O^{+}})$ ion in pure water at $298 \ K$ is:

The $pH$ of water at $25\,^oC$ is nearly