Which of the following is an oxidation-reduction reaction? fe2o3 + 3co mc009-1.jpg 2fe + 3co2 cuso4 + 2naoh mc009-2.jpg cu(oh)2 + na2so4 2naoh + h2co3 mc009-3.jpg na2co3 + 2naoh pb(no3)2 + na2so4 mc009-4.jpg 2nano3 + pbso4

is an oxidation-reduction reaction.

Explanation:

In an oxidation-reduction reaction, the oxidation number of some elements must change during reaction.

represents an oxidation-reduction reaction.

                                                                    oxidation number

                             Fe in                       +3

                    Fe in Fe                                                        0

                    C in CO                                                        +2

                                C in                                  +4

SO, oxidation number of Fe decreases during reaction. Hence is being reduced. Also, oxidation number of C increases during reaction. Hence CO is being oxidized.

In all other given reactions, oxidation number of elements are not changed during reaction. Hence they are not oxidation-reduction reaction.