Question

when a green iron salt is heated strongly its colour finally , change to black and odours (smell) of burning sulphur is given out .

Answer 1

Heya friend :-)

Here is your answer

1) coz the salt is Ferrous Sulphate

2) Thermal decomposition is taking place

3) it's balanced equation is:

2 FeSO4 (s)
Heat → Fe2O3 (s)+ SO2 (g) + SO3 (g)
Ferrous sulphate Ferric oxide
Green Colored Reddish brown