Q.Give reasons.
Ga3+ salts are better reducing agent while Tl3+ salts are better oxidising agent.

Note on the question as printed. As printed, the question names 'Ga3+ salts' as the reducing agent — but Ga3+ cannot act as a reducing agent in the usual sense, since group 13's maximum oxidation state is +3 and there is no higher state for Ga3+ to be oxidised to. The chemically coherent version of this standard comparison (matching the book's own logic in Problem 9.4) is between Ga+ (not Ga3+) and Tl3+; this discrepancy is flagged here rather than silently answered as printed.

Step 1. Inert-pair effect down group 13. Section 9.4.1 explains that the lower (+1) oxidation state becomes increasingly stable, relative to the group (+3) state, going down group 13.

Step 2. Apply to gallium (an early, lighter member). For gallium, +3 is still the more stable, 'normal' oxidation state; a Ga+ ion, if formed, is relatively unstable and would readily lose its electron pair to reach the more stable Ga3+ — that is, Ga+ readily gets oxidised, so it (Ga+, not Ga3+) behaves as a reducing agent. …

Applying the inert-pair-effect stability trend from section 9.4.1/Problem 9.4 to each end of group 13, while flagging the apparent Ga3+/Ga+ inconsistenc …

• Treating 'Ga3+ salts are reducing agents' literally, which is not chemically meaningful since +3 is group 13's maximum oxidation state — there is nowhere higher for Ga3+ to be oxidised to. …