Science (086) — AI-generated practice question

When ferrous sulphate (FeSO₄) crystals are heated, their colour changes from green to white (as water of crystallisation is lost), and then to a reddish-brown solid. The reaction is:

$$2\text{FeSO}_4(s) \xrightarrow{\Delta} \text{Fe}_2\text{O}_3(s) + \text{SO}_2(g) + \text{SO}_3(g)$$

The products formed are ferric oxide (Fe₂O₃), sulphur dioxide (SO₂), and sulphur trioxide (SO₃). A characteristic smell of burning sulphur is also observed.

Source: Chapter 1, Section 1.2.2 – Decomposition Reaction

• The question is worth 2 marks: 1 mark for colour change, 1 mark for products (equation or names).
• Mention both stages of colour change (green → white → reddish-brown) for full credit, since the textbook specifies crystals lose water first, then decompose.
• Writing the balanced equation counts as identifying products — examiners accept either the equation or naming all three products.
• The type of reaction (thermal decomposition) may earn bonus credit if space allows.