Question

Write the formulas of the compound NH4+ formed by specified cations with the following anions:OH-, NO3-, CO3-2,HSO4-, PO4-3 . Use the given order of anions

Answer 1

There is no NH4OH although some people still use that as the product of NH3 + H2O. It has been shown not to exist.
NH4NO3
(NH4)2CO3
NH4HSO4
(NH4)3PO4