Question

What is the colour of ${\text{FeSO}}_4.7{\text{H}}_2\text{O}$ crystals? How does this colour change upon heating and what are the products formed? [3 MARKS]

Answer 1

Each point: 1 Mark

1. Hydrated ferrous sulphate crystals are green in colour. On heating, single reactant breaks down to give simpler products. This is a decomposition reaction.

2. Ferrous sulphate crystals (${\text{FeSO}}_4.7{\text{H}}_2\text{O}$) lose water when heated and the colour of the crystals changes.

3. It then decomposes to ferric oxide (${\text{Fe}}_2{\text{O}}_3$), sulphur dioxide (${\text{SO}}_2$) and sulphur trioxide (${\text{SO}}_3$). Ferric oxide is a solid, while ${\text{SO}}_2$ and ${\text{SO}}_3$ are gases.