Question

While performing an experiment a student observes that when he heats some green crystals in a boiling tube, the colour of the crystals changes to brown and a gas evolves which smells like burning sulphur. Interpret the observations and results.

Answer 1

Observation: The green colour of ferrous sulphate crystals changes to brownish black ferric oxide and smell of burning sulphur is observed.

Result: Heating of ferrous sulphate is a thermal decomposition reaction because of ferrous sulphate breaks down into simpler compounds-Fe₂O₃, SO₂ and SO₃.

2FeSO₄(s) +Heat → Fe₂O₃(s) + SO₂(g) + SO₃(g)