The correct option is A S2−(aq)+4I2(s)+4H2O(l)⟶8I−(aq)+SO2−4(aq)+8H+(aq)
The unbalanced chemical equation is given below:
S2−(aq)+I2(s)⟶SO2−4(aq)+I−(aq)
Balance all atoms except H and O,
S2−(aq)+4I2(s)⟶SO2−4(aq)+8I−(aq)
The oxidation number of S changes from −2 to +6.
The net change in the oxidation number is 8.
The oxidation number of iodine changes from 0 to −1.
The net change in the oxidation number per I atom is 1.
Total change in the oxidation number for 8 I atoms is 8.
Thus, the increase in the oxidation number is equal to the decrease in the oxidation number.
Balance O atoms by adding 4 water molecules to LHS,
S2−(aq)+4I2(s)+4H2O(l)⟶8I−(aq)+SO2−4(aq)
Balance H atoms by adding 8 H+ to the RHS,
S2−(aq)+4I2(s)+4H2O(l)⟶8I−(aq)+SO2−4(aq)+8H+(aq)
This is the balanced chemical equation.