Ammonium sulphate, (NH₄)₂SO₄, is made by reacting dilute sulphuric acid with excess ammonia and then evaporating the solution. Dilute sulphuric acid can also be used to prepare hydrated iron(II) sulphate of formula FeSO₄.XH₂O and relative molecular mass 278.

1. aState a use for ammonium sulphate. [1]
2. bDescribe a positive chemical test for ammonium ions. [3]
3. cCalculate the value of X in the formula. [3]
4. dCalculate the percentage of water by mass in hydrated iron(II) sulphate. [1]

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