200 cc of x 10⁻³ M potassium dichromate is required to oxidise 750 cc of 0.6 M Mohr's salt solution in acidic medium. Here x= _ _ _ _ .

Step-by-step solution

Mohr's salt ( FeSO₄ (NH₄)₂SO₄ 6H₂O ) is a source of Fe²⁺ ions. The redox reaction with potassium dichromate in acidic medium is: 6Fe²⁺ + Cr₂O₇²⁻ + 14H^+ 6Fe³⁺ + 2Cr³⁺ + 7H₂O . Moles of Fe²⁺ from Mohr's salt solution: n(Fe²⁺) = 0.6 M 0.750 L = 0.45 mol . From the stoichiometry, 6 moles of Fe²⁺ require 1 mole of Cr₂O₇²⁻ . Moles of Cr₂O₇²⁻ required: n(Cr₂O₇²⁻) = 0.45 6 = 0.075 mol . Molarity of potassium dichromate: M = 0.075 mol 0.200 L = 0.375 M = 375 10⁻³ M . Therefore, x = 375 .