Question

Ionic product of water increases with the ...........................temperature.

• A. increase
• B. decrease
• C. constant
• D. None of these

Answer 1

The correct option is A increase

The ionic product of water increases with increases in temperature.

The formation of hydrogen ions (hydroxonium ions) and hydroxide ions from water is an endothermic process. Using the simpler version of the equilibrium:

$H_{2}O\left(l\right)$ $\leftrightarrow$ $H^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$

The forward reaction absorbs heat.

According to Le Chatelier, if you increase the temperature of the water, the equilibrium will move to lower the temperature again. It will do that by absorbing the extra heat.

That means that the forward reaction will be favoured, and more hydrogen ions and hydroxide ions will be formed. The effect of that is to increase the value of Kw as temperature increases.