Consider the following pairs of reactions and properties: I. Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g) — Fe is reductant II. Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) — Cu is being reduced III. Br2(l) + 2I−(aq) → 2Br−(aq) + I2(s) — Br2 is reductant IV. CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) — C atom in CH4 is oxidized. Which of the above pairs are correct?
A.I and II only
B.II, III and IV
C.I, II and IV✓ Correct
D.I, III and IV
Explanation
I. Fe goes from oxidation state 0 to +2, losing electrons — Fe is the reductant. Correct. II. Cu in CuSO4 goes from +2 to 0, gaining electrons — Cu is being reduced. Correct. III. Br2 goes from 0 to −1 (gain of electrons), so Br2 is the OXIDANT, not reductant. I− is the reductant. Hence III is incorrect. IV. Carbon in CH4 (oxidation state −4) becomes +4 in CO2 — C is oxidized. Correct. Therefore I, II and IV are correctly matched.
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