Question

Which of the following is an oxidation-reduction reaction?
Fe2O3 + 3CO Right arrow. 2Fe + 3CO2
CuSO4 + 2NaOH Right arrow. Cu(OH)2 + Na2SO4
2NaOH + H2CO3 Right arrow. Na2CO3 + 2NaOH
Pb(NO3)2 + Na2SO4 Right arrow. 2NaNO3 + PbSO4

Answer 1

Only the first reaction is an oxidation–reduction reaction.

Fe2O3 + 3CO → 2Fe + 3CO2

Oxidation numbers:
- Fe in Fe2O3 is +3 → Fe(0) (reduced).
- C in CO is +2 → C in CO2 is +4 (oxidized).

The others are double-displacement or acid–base reactions with no change in oxidation states:
- CuSO4 + 2NaOH → Cu(OH)2 + Na2SO4 (precipitation)
- 2NaOH + H2CO3 → Na2CO3 + 2H2O (acid–base neutralization; the equation as given was likely misprinted)
- Pb(NO3)2 + Na2SO4 → 2NaNO3 + PbSO4 (precipitation)