CE CHEM

The question should be:
Which of the following solutions would not undergo a colour change when mixed with sodium sulphite solution
A. iodine solution
B. acidified potassiun permanganate solution
C. chromium(III) sulphate solution
D. iron(III) sulphate solution

The answer is C.

Sulphite ion is a reducing agent.

A.
Iodine solution is an oxidizing agent, and it undergoes redox reaction with sulphite ion. The brown iodine solution is reduced to colourless iodide ion.
SO32-(aq) + I2(aq) + H2O(l) → SO42-(aq) + 2I-(aq) + 2H+(aq)

B.
Acidified potassium permanganate solution is an oxidizing agent, and it undergoes redox reaction with sulphite ion. The purple permanganate ion is reduced to colourless manganese(II) ion.
2MnO4-(aq) + 6H+(aq) + 5SO32-(aq) → 2Mn2+(aq) + 3H2O(l) + 5SO42-(aq)

C.
No reaction occurs between sodium sulphite solution and chromium(III) sulphate solution, because the oxidizing power of chromium(III) ion is not strong enough.

D.
Iron(III) ion is an oxidizing agent, and it undergoes redox reaction with sulphite ion. The yellowish brown iron(III) ion is reduced to pale green iron(II) ion.
SO32-(aq) + 2Fe3+(aq) + H2O(l) → SO42-(aq) + 2Fe2+(aq) + 2H+(aq)
=

Colorless sodium sulphite solution can act as a reducing agent or bleaching agent. It can oxidise to colorless sodium sulphate solution.
A : Aqueous iodine is brown. It reacts with sodium sulphite solution to give colorless iodide ions.

B : Purple acidfied potassiun permanganate solution reacts with sodium sulphite solution to give pale pink Maganese(III) ions.

C : Green chromium(III)sulphate solution cannot be reduced by sodium sulphate solution. So no color change when mixing.

D : Yellow iron(III)sulphate solution reacts with sodium sulphite solution to give pale green iron(II) ions.

The answer is C.