The self-ionization of water, also known as autoionization, is a process where water molecules spontaneously dissociate into hydronium ions (H3O+) and hydroxide ions (OH-).

 The self-ionization of water, also known as autoionization, is a process where water molecules spontaneously dissociate into hydronium ions (H3O+) and hydroxide ions (OH-). 

Here's a more detailed explanation:

What it is:

In pure water or aqueous solutions, a small percentage of water molecules donate a proton (H+) to another water molecule. 

The Reaction:

This process can be represented as: 2H₂O(l) ⇌ H₃O⁺(aq) + OH⁻(aq). 

Key Ions:

The resulting ions are hydronium ions (H3O+) and hydroxide ions (OH-). 

Equilibrium Constant:

The equilibrium constant for this reaction is called the ion-product constant of water (Kw) and is defined as Kw = [H3O+][OH⁻]. 

Kw Value:

At 25°C, Kw is approximately 1.0 x 10⁻¹⁴. 

Neutral Water:

In pure water, the concentrations of hydronium and hydroxide ions are equal, and the water is considered neutral. 

Acidic/Basic Solutions:

If a solution has a higher concentration of hydronium ions than hydroxide ions, it's acidic; if it has a higher concentration of hydroxide ions, it's basic. 

Temperature Dependence:

The extent of ionization and the resulting concentrations of hydronium ion and hydroxide ion increase with temperature.