a. Chemical reaction takes place in test tube (ii) only.
b. These chemical reactions are called displacement reactions.
c. Chemical equation: (including oxidation states)
Mg° (s) + Fe2+ S6+ O42- (aq) → Mg2+S6+O2-4 (aq) + Fe° (s)
At Mg : Mg°(s) → Mg2+ (aq) + 2e- (oxidation)
At Fe2+ , Fe2+ (aq) + 2e- → Fe°(s) (reductipn)