Question

Is the self ionization of water endothermic or exothermic? The ionization constant for water (Kw) is 2.9 10−14 at 40 °C and 9.6 10−14 at 60 °C.

Answer 1

It is endothermic

Step-by-step explanation:

Now let us look at the figures in the question. At 40°c, the Kw is 2.9*10-14 but at 60°c, it is 9.6*10-14

Now the auto ionization of water is represented by the equation

H2O double arrow H^+ + OH-

The higher Kw at a higher temperature implies that the equilibrium position shifts towards the right (more dissociation/ionization of water molecules). Remember that increase in temperature shifts the equilibrium position of an endothermic reaction towards the right (more products are formed). Hence the self ionization of water must be an endothermic process