Can H2O act as a lewis acid, lewis base, or both?
Water can act as both a Lewis acid and a Lewis base.
Water is amphoteric: this means that it can act both as an acid and as a base. The reason for this is that water is self-ionising. Observe the following equation:
This reaction is reversible, because the hydronium ion (
As mentioned above, since the hydronium and hydroxide ions are quite strong acids and bases, respectively, the self-ionisation of water allows it to function both as a Lewis acid and as a Lewis base via protonation.