500 mL of 0.2 M MnO₄⁻ solution in basic medium when mixed with 500 mL of 1.5 M KI solution, oxidises iodide ions to liberate molecular iodine. This liberated iodine is then titrated with a standard x M thiosulphate solution in presence of starch till the end point. If 300 mL of thiosulphate was consumed, then the value of x is _____.
Answer: 1
Solution
In basic medium permanganate gains three electrons, , so its equivalents are . Iodide supplies equivalents, so permanganate is the limiting reagent and 0.3 equivalents of iodine are set free. Thiosulphate reacts with iodine in a one-electron change, so its equivalents equal those of the iodine: , which gives .
JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Integer answer