Cu+(aq.) is less stable than Cu2+(aq.) but Fe3+(aq.) is more stable than Fe2+(aq.). — d and f Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: Balance the electron transfer between the reduction of persulfate (gains 2e^- per mole) and the oxidation of manganese (loses 5e^- per mole). Step 2: To equate the electrons lost and gained, multiply the reduction half-reaction by 5 and the oxidation half-reaction by 2. This gives: 5S2O8^2- + 10e^- ---> 10SO4^2- and 2Mn^2+ + 8H2O ---> 2MnO4^- + 16H^+ + 10e^-. Step 3: This shows that 5 moles of S2O8^2- are required to oxidize 2 moles of Mn^2+. Therefore, 2.5 moles of S2O8^2- are needed per 1 mole of Mn^2+, which corresponds to option (a).