A metal sulphate (A) on heating evolves two gases (B) and (C) and an oxide (D).
Gas (B) turns \(K_2Cr_2O_7\) paper green while gas (C) forms a trimer in which there
is no \(S-S\) bond. Oxide (D) with conc. \(HCl\) forms a Lewis acid (E) which exists
in a dimer. Compounds (A), (B), (C), (D) and (E), respectively, are:
1. \(FeSO_4, SO_2,Fe_2O_3,FeCl_3\)
2. \(Al_2(SO_4)_3,SO_2,SO_3,Al_2O_3,FeCl_3\)
3. \(FeS,SO_2,SO_3,FeSO_4,FeCl_3\)
4. \(FeS,SO_2,SO_3,Fe_2(PO_4)_3,FeCl_2\)