( KMnO ₄ ) oxidises ( S ₂ O ₃²⁻ ) to ( SO ₄²⁻ ) in medium (x ) and ( NO ₂⁻ )to ( NO ₃⁻ )in medium (y, x ) and (y ) are respectively

Step-by-step solution

In neutral or faintly alkaline solution, ( aligned 8 MnO ₄⁻+3 ~S ₂ O ₃⁻²+ H ₂ O & 8 MnO ₂ + 6 SO ₄⁻²+2 OH ⁻ aligned ) In acidic medium, (2 MnO ₄⁻+5 NO ₂⁻+6 H ⁺ 2 Mn ⁺²+5 NO ₃⁻+3 H ₂ O ) Hence, option (4) is correct.