How many grams of potassium dichromate are required to oxidise 20.0 g of Fe ²⁺ in FeSO ₄ to Fe ³⁺ if the reaction carried out in an acidic medium? Molar mass of K ₂ Cr ₂ O ₇ and FeSO ₄ are 294 and 152 respectively.

Step-by-step solution

aligned Number of moles of FeSO ₄ & = 20 ~g 152 ~g ~mol ⁻¹ & =0.132 ~mole aligned The balance ionic equation of redox reaction is Cr ₂ O ₇²⁻+6 Fe ²⁺+14 H ⁺ 2 Cr ³⁺+6 Fe ³⁺+7 H ₂ O 6 moles of Fe ²⁺=1 mole of K ₂ Cr ₂ O ₇ 0.132 mole of Fe ²⁺= 1 6 0.132 =0.022 moles of K ₂ Cr ₂ O ₇ Mass of K ₂ Cr ₂ O ₇ in 0.02 moles =0.022 294=6.5 ~g