Given below are two statements:
Statement I: In the oxalic acid vs KMnO₄ (in the presence of dil H₂ SO₄ ) titration the solution needs to be heated initially to 60° C, but no heating is required in Ferrous ammonium sulphate (FAS) vs KMnO₄ titration (in the presence of dil H₂ SO₄)
Statement II: In oxalic acid vs KMnO₄ titration, the initial formation of MnSO₄ takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs KMnO₄, heating oxidizes Fe²⁺ into Fe³⁺ by oxygen of air and error may be introduced in the experiment.
In the light of the above statements, choose the correct answer from the options given below

Solution

Chemistry ma’am · 3 steps

Warm the oxalate to get it started; never warm the ferrous solution, because air will steal your Fe(II).

1. 2MnO₄⁻ + 5C₂O₄²⁻ + 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O

2. Oxalic acid titration. At room temperature this reaction is very slow, so the first drops of KMnO₄ stay pink for a long time. Heating to about 60°C starts it, and the Mn²⁺ (as MnSO₄) it forms then catalyses the rest of the reaction. This is autocatalysis, so Statement I's heating step and Statement II's reason are both correct.
3. FAS titration. MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O is fast even when cold, so no heating is needed. Heating would actually hurt: air oxidises some Fe²⁺ to Fe³⁺, less KMnO₄ is used, and the result comes out wrong.
4. So. Statement I describes the correct procedure and Statement II gives the correct chemistry behind it. Both are true, which is option (c).

The idea to keep. Oxalate with permanganate is slow at first and is autocatalysed by Mn²⁺, so it needs heat. Fe²⁺ reacts fast and is easily oxidised by air, so keep it cold.

Answer from the NTA final answer key. Solution by PrepWiser.