CBSE Class 10 Science 2020 · Paper 31/C/2 · Question 15

(i) Before heating the crystals are green; on heating they first turn white as they lose their water of crystallisation, and finally a reddish-brown solid, ferric oxide (${\text{Fe}}_2{\text{O}}_3$), is left. (ii) Sulphur dioxide (${\text{SO}}_2$) and sulphur trioxide (${\text{SO}}_3$); the smell of burning sulphur comes from the ${\text{SO}}_2$. (iii) Thermal decomposition reaction. (iv) $2{\text{FeSO}}_4(s)\stackrel{\text{heat}}{\to }{\text{Fe}}_2{\text{O}}_3(s)+{\text{SO}}_2(g)+{\text{SO}}_3(g)$