MnO2 is the most important oxide of manganese. MnO2 occurs naturally as the black coloured mineral p — d and f Block Elements Chemistry Question
Question
MnO2 is the most important oxide of manganese. MnO2 occurs naturally as the black coloured mineral pyrolusite. It is an oxidising agent, and decomposes to Mn3O4 on heating to 530°C. It is used in the preparation of potassium permanaganate and in the production of Cl2 gas. Over half a million tonnes per year of MnO2 is used in dry batteries. [3, 4]
💡 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).