Question

explain the term ' ionic product of water and ' pH value ; how does
the former change with temprature

Answer 1

pure water is a weak electrolyte and it undergo self ionization or auto-protolysis. In this process water molecules splits into  hydrogen ion (H+) and hydroxide ion (OH-).
the concentration of undissociated water molecules, [H20], may be regarded as constant. Thus, the product #[H20] gives another constant which is designated as Kw. So,

[H+][OH-] = Kw

The constant, Kw, is termed as ionic product of water.
is only because of the self ionization of water that it can act as both acid as well as base.

Any substance which increases the concentration of H+ ion would make water acidic.

Similarly, any substance which increases the concentration of OH- ion, would make water basic.

But in pure water, the hydrogen ion (hydroxonium ion) concentration is always equal to the hydroxide ion concentration. For every hydrogen ion formed, there is a hydroxide ion formed as well.hope help