Question
Class 11ChemistryRedox Reactions

Identify the oxidant and reductant in the following reactions:

(a) 10H+(aq) + 4Zn(s) + NO3−(aq) ⟶ 4Zn2+(aq) + NH4+(aq) + 3H2O(l)

(b) I2(g) + H2S(g) ⟶ 2HI(g) + S(s)

Verified Answer

(a) Writing the O.N. of all the atoms above their symbols, we have,

Uploaded image

Here, there is no change in the O.N. of H and O-atoms. But the O.N. of Zn changes from zero in Zn to +2 in Zn2+, therefore, it is oxidized and hence Zn acts as a reductant.

The O.N. of N decreases from +5 in NO–3 to –3 in NH+4 and, therefore, it is reduced and hence NO–3 acts as the oxidant.

(b) Writing the O.N. of all the atoms above their symbols, we have,

Uploaded image

Here, O.N. of H does not change. The O.N. of I2 decreases from zero in I2 to –1 in HI, therefore, I2 is reduced and hence it acts as an oxidant. The O.N. of S increases from –2 in H2S to zero in S, therefore, H2S is oxidized and hence it acts as the reductant.