Select the incorrect statement out of the following.

• A

  Molar concentration of hydronium ion expressed in base 10 logarithmic scale is called ${\mathrm{P}}^{\mathrm{H}}$ scale.

• B

  ${\mathrm{P}}^{\mathrm{H}}$ of solution is the negative logarithm in base 10 of ${\mathrm{H}}^{+}$ ion activity $\left({\mathrm{a}}_{{\mathrm{H}}^{+}}\right),$ numerical value of molarity of solution.

• C

  ${\mathrm{P}}^{\mathrm{H}} = -{\log }_{10}{\mathrm{a}}_{{\mathrm{H}}^{+}}=-\log \frac{\left[{\mathrm{H}}^{+}\right]}{\mathrm{mol} {\mathrm{L}}^{-1}}$

• D

  $\left[{\mathrm{H}}_3{\mathrm{O}}^{+}\right]\times \left[{\mathrm{OH}}^{-}\right]$ is ${10}^{-14} {\mathrm{M}}^2$ for any aqueous solution at any temperature.