Final answer:
The reduction of La(NO₃)₃ to La(NO₂)₃ is a redox reaction involving the conversion of nitrate to nitrite with tin acting as the reducing agent.
Step-by-step explanation:
The reduction of La(NO₃)₃ to La(NO₂)₃ involves a redox reaction where the nitrate ion (NO₃-) is reduced to nitrite (NO₂-). This process typically occurs in stages, starting with the reduction of nitrate to nitric oxide (NO), followed by further reaction, in presence of oxygen, to form nitrite, giving the characteristic red-brown color of NO₂.
The metallic tin (Sn) acts as the reducing agent in this context, being oxidized from Sn(s) to Sn²+ (aq), as demonstrated by the equation Sn(s) → Sn²+ (aq) + 2 e-. In electrochemical terms, the reduction reaction occurs at the cathode, while the oxidation occurs at the anode.