Question

Which represents the self-ionization of water at 25°C? H2O + H2O 2H2 + O2 H2O + H2O H2O2 + H2 H2O + H2O 4H+ + 2O2- H2O + H2O H3O+ + OH-

Answer 1

The fourth answer is correct 
H20 + H20  H30 + 0H-

Answer 2

Answer: Option (d) is the correct answer.

Explanation:

When molecules of same substance combine together to result in the formation of ions then this type of reaction is known as self-ionization.

For example, $H_{2}O + H_{2}O \rightarrow H_{3}O^{+} + OH^{-}$

So, here two molecules of water are combining and they result in the formation of hydronium ion ($H_{3}O^{+}$) and hydroxide ion ($OH^{-}$).

Hence, this reaction is a self-ionization reaction.