NH3(aq)+H2O(l)⇌NH4+(aq)+OH−(aq) N H 3 ( a q ) + H 2 O ( l ) ⇌ N H 4 + ( a q ) + O H − ( a q ) H2O H 2 O is the acid (proton donor); NH3 N H 3 is the base (proton acceptor). NH3 N H 3 is the acid (proton donor); H2O H 2 O is the base (proton acceptor). NH3 N H 3 is the acid (proton acceptor); H2O H 2 O is the base (proton donor). H2O H 2 O is the acid (proton acceptor); NH3 N H 3 is the base (proton donor).