Name the substance oxidised and the substance reduced, and also identify the oxidising agent and reducing agents in the following reactions :
(a) `3MnO_(2) +4Al to 3Mn +2Al_(2)O_(3)`
(b) `Fe_(2)O_(3) + 3CO to 2Fe + 3CO_(2)`
(c) `SO_(2) + 2H_(2)S to 3S +2H_(2)O`

Explanation

Writing the oxidation numbers of all atoms involved in the given reaction, we have

From the above it is clear that the oxidation number of Al increases from 0 to +3. Hence, Al undergoes oxidation and acts as a reducing agent. In `MnO_(2)`, the oxidation number of Mn decreases from +4 to 0. Therefore, `MnO_(2)` undergoes reduction and acts as an oxidising agent.