JEE Main20262 April 2026Morning ShiftChemistryd and f Block ElementsActual
Which of the following sets includes all the species that will change the orange colour of K₂Cr₂O₇ in acidic medium?
Options
- AFe²⁺, Sn²⁺, I^-, S²⁻
- BS²⁻, Fe³⁺, I^-, C₂O₄²⁻
- CFe²⁺, NO₂^-, SO₂, Sn⁴⁺
- DFe³⁺, SO₄²⁻, S²⁻, Sn⁴⁺
Correct answer
A. Fe²⁺, Sn²⁺, I^-, S²⁻
Step-by-step solution
K₂Cr₂O₇ in acidic medium acts as a strong oxidizing agent. It changes its colour from orange ( Cr₂O₇²⁻ ) to green ( Cr³⁺ ) when it reacts with a reducing agent. We need to identify the set in which all species can act as reducing agents (i.e., they can be oxidized to a higher oxidation state). In option (A), Fe²⁺ oxidizes to Fe³⁺ , Sn²⁺ oxidizes to Sn⁴⁺ , I^- oxidizes to I₂ , and S²⁻ oxidizes to S . All of these are reducing agents. In option (B), Fe³⁺ is already in its maximum stable oxidation state and cannot be