(d) The formula of ammonium sulfate is (NH₄)₂SO₄ - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2016 - Paper 1

To determine the empirical formula of ammonium sulfate (NH₄)₂SO₄, we first need to identify the ratio of each element in the compound:

1. Identify the composition: The chemical formula has 2 ammonium ions (NH₄) and one sulfate ion (SO₄).

   • From (NH₄)₂: It provides 2 nitrogen (N) atoms and 8 hydrogen (H) atoms.
   • From SO₄: It provides 1 sulfur (S) atom and 4 oxygen (O) atoms.

2. Count total atoms:

   • Nitrogen (N): 2
   • Hydrogen (H): 8
   • Sulfur (S): 1
   • Oxygen (O): 4

3. Find the greatest common divisor: The counts of each type of atom can be reduced by dividing them by the largest number of moles in the formula, which in this case is 1 (for S).

4. Simplify the ratio: This gives us:

   • N : H : S : O = 2 : 8 : 1 : 4.

5. Divide by common factor: By dividing all elements by the smallest number of moles (which in this case is 1), we can simplify the ratio:

   • N : H : S : O = 2 : 8 : 1 : 4 remains as 2, 8, 1, and 4.

6. Empirical formula: The simplest whole number ratio corresponds to:

   • The empirical formula can then be represented as:

   ( NH_{4}SO_{4} )

Thus, while the empirical formula may seem to remain the same, the correct form to express is simply its basic elements in their simplest ratio.

So, the empirical formula of ammonium sulfate can be expressed as: Empirical Formula: $NH_4SO_4$.