MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

In a dry cell, the reaction at the cathode involves the reduction of manganese dioxide (MnO_2). The cathode reaction is: MnO_2 + NH_4^+ + e^- MnO(OH) + NH_3 The oxidation state of Mn in MnO_2 is +4. The oxidation state of Mn in MnO(OH) is +3. The oxidation number of Mn changes from +4 to +3. Thus, the oxidation number of Mn decreases by 1. Answer: decreases by 1