The conjugate acid of H2O is H3O+, also known as the hydronium ion.
When water (H2O) acts as a base, it can accept a proton (H+). This process forms the hydronium ion (H3O+). The reaction can be represented as follows:
H2O + H+ → H3O+
In this reaction, water gains a proton, making it the conjugate acid of the original water molecule. The hydronium ion is a key species in many chemical reactions, especially in aqueous solutions where it plays a crucial role in acid-base chemistry.