Solution:
(a)
(i) V2+ and Cr3+ are most stable as they both have the [Ar]3d3 or 𝑡32g stable electronic configuration.
(ii) Mn3+ ions are the strongest oxidising agent in the aqueous solution because after converting to Mn2+ they get stable half-filled d5 electronic configuration.
(iii) Ti4+ has no electron in d orbital. No d-d transition is possible in this case. Therefore, it is colourless.
(b)
(i)
(ii)
