Name of the gas/gases evolved when crystals of ferrous sulfate are heated strongly?

1. When crystals of ferrous sulphate are heated then they lose water of crystallization.
2. ${\mathrm{FeSO}}_4.7{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\stackrel{∆}{\to }{\mathrm{FeSO}}_4\left(\mathrm{s}\right)+7{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

If we heat crystals further then ${\mathrm{FeSO}}_4$ releases sulphur dioxide $\left({\mathrm{SO}}_2\right)$ and sulphur trioxide $\left({\mathrm{SO}}_3\right)$ gases and gets converted into ferric oxide $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$.

Reaction Involved:

$2{\mathrm{FeSO}}_4\left(\mathrm{s}\right)\stackrel{∆}{\to }{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{SO}}_3\left(\mathrm{g}\right)$

Hence, sulphur dioxide $\left({\mathrm{SO}}_2\right)$ and sulphur trioxide $\left({\mathrm{SO}}_3\right)$ gases are evolved when crystals of ferrous sulfate are heated strongly.