Consider the equation for the dissociation of water:

$$\begin{array}{*{20}{l}} {{{\text{H}}_2}{\text{O(l)}} \rightleftharpoons {{\text{H}}^ + }{\text{(aq)}} + {\text{O}}{{\text{H}}^ - }{\text{(aq)}}}&{\Delta H = + 57.3{\text{ kJ}}\,{\text{mo}}{{\text{l}}^{ - 1}}} \end{array}$$

Which statement is correct?

A.     The pH of pure water is always 7.

B.     At temperatures above 298 K the pH of pure water is below 7.

C.     At temperatures above 298 K the pH of pure water is above 7.

D.     ${K_{\text{w}}}$ decreases with increasing temperature.

B