Ammonium sulphate will dissolve in water.

Ammonium sulphate (Amm. sulf. henceforth) is a salt of a strong acid and a weak base. And hence like any other such salt, it will make the aqueous solution slightly acidic.

On getting dissolved in water, like anyother salt, ionisation takes place and the ammonium ions and the sulphate ions are formed.Furthermore, NH4OH itself equilibrates with the ammonia (NH3) gas and hence the solution gives off quite an ammoniacal smell (unpleasant odour).SO4–2 remains as it is just dissolved in water.