How does NH4OH H2SO4 form a double displacement reaction?

When NH4OH and H2SO4 are mixed, they react to form NH4+ and SO4^2- ions through a double displacement reaction. The ammonium ion (NH4+) combines with the sulfate ion (SO4^2-) to form ammonium sulfate (NH4)2SO4. The double displacement occurs because the cations and anions exchange partners between the reactants.