Given below are two statements:
Statement I : S₈ solid undergoes disproportionation reaction under alkaline conditions to form S²⁻ and S₂ O₃ ²⁻.
Statement II : ClO₄⁻ can undergo disproportionation reaction under acidic condition.
In the light of the above statements, choose the most appropriate answer from the options given below :

Solution

Chemistry ma’am · 4 steps

To disproportionate, an element must be able to go both up and down. Check that for each one.

1. What disproportionation needs. One element is oxidised and reduced at the same time. So it must sit at an intermediate oxidation state, with room to rise and room to fall.
2. Statement I. Sulfur in S₈ is at 0, between its lowest state of -2 and its highest of +6. In hot alkali it goes down to S²⁻ (-2) and up to S₂O₃²⁻ (average +2).

   S₈ + 12OH⁻ → 4S²⁻ + 2S₂O₃²⁻ + 6H₂O

3. Check and Statement II. Four S atoms gain 2 electrons each and four lose 2 each, so 8 electrons balance and Statement I is correct. In ClO₄⁻, Cl is at +7, its maximum oxidation state, so it cannot be oxidised further and Statement II is incorrect.
4. So. Statement I is correct and Statement II is incorrect, which is option (a).

The idea to keep. An element in its highest or lowest oxidation state can never disproportionate. Look for an intermediate state that can move both ways, like S at 0 or Cl in ClO⁻.

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