Question

State True or False.

(B) is $S{O}_2$.

• A. True
• B. False

Answer 1

The correct option is A True

Compound (A) is a light green crystalline solid.
It is hydrated ferrous sulphate $FeS{O}_4.7H_{2}O$
Ferrous sulphate is dissolved in dil.sulphuric acid.
When $KMn{O}_4$ is added ferrous sulphate is oxidized to ferric sulphate and Mn(VII) ions are reduced to Mn(II) ions. Hence, the pink colour of $KMn{O}_4$ disappears. When ferrous sulphate is strongly heated, sulphur dioxide gas (compound B) , sulphur trioxide gas (compound C) and a residue of ferric oxide (compound D) are obtained.
$2FeS{O}_4\stackrel{strongheating}{\to }F{e}_2{O}_3+S{O}_2\uparrow +S{O}_3\uparrow$.
When the mnixture of sulphur dioxide and sulphur trioxide is passed through dichromate solution, sulphur dioxide reduces dichromate ion ions to green coloured Cr(III) ions.
$C{r}_2{O}_7^{2-}+2H^{+}+3S{O}_2\to 2C{r}^{3+}+3S{O}_4^{2-}+5H_{2}O$
This solution containing sulphate ions on treatment with barium nitrate gives white ppt of barium sulphate which is compound E.
$Ba(N{O}_3{)}_2+S{O}_4^{2+}\to \underset{whiteppt}{BaS{O}_4\downarrow }+2N{O}_3^{-}$
When ferric oxide is heated with charcoal in reducing flame, it is reduced to iron.
$F{e}_2{O}_3+3C\stackrel{heat}{\to }2Fe+3CO$