Which of the following salts gives a mixture of ${\mathrm{SO}}_2$ and ${\mathrm{SO}}_3$ on heating?

${\mathrm{FeSO}}_4$ salts gives a mixture of ${\mathrm{SO}}_2$ and ${\mathrm{SO}}_3$ on heating

Iron sulphate crystals become anhydrous ferrous sulphate ${\mathrm{FeSO}}_4$ when heated, losing their water content in the process. They so turn from a bright green to a white colour. Anhydrous ferrous sulphate breaks down into sulphur dioxide ${\mathrm{SO}}_2$, sulphur trioxide, and ferric oxide ${\mathrm{Fe}}_2{\mathrm{O}}_3$ with further heating ${\mathrm{SO}}_3$.

Hence option B is correct