Question

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

Answer 1

The green crystals are ferrous sulphat which when heated, form ferous oxidr ii , brown colored crystals and sulphur dioxide and trioxide are released.

Answer 2

The reaction is 2FeSO4 → Fe2O3 + SO2 + SO3. The brown crystal is Fe2O3. SO2 and SO3 are pungent smelling gases. This is thermal decomposition reaction.