Question

0.400 g of impure caso4 (molar mass = 136) solution when treated with excess of barium chloride solution, gave 0.617 g of anhydrous baso4 (molar mass = 233). The percentage of caso4 present in the sample is

Answer 1

Given 0.400g of impure CaSO4 treated with BaCl2 gave 0.617g of BaSO4

CaSO4 + BaCl2 --> BaSO4
136g 233g

▶️ To calculate mass of CaSO4 which produces 0.617g of BaSO4
From the chemical eqn.
233g of BaSO4 are produced from CaSO4 = 136g
Therefore, 0.617g of it would be produced from CaSO4 = 136/233 * 0.617 = 0.360g

This is the mass of pure CaSO4 present in 0.004g of impure sample.

▶️ To calculate percentage purity of impure sample

0.004g of impure sample contains pure CaSO4 = 0.360g
Therefore, 100g of impure sample will contain pure CaSO4 = 0.360/0.400 * 100 = 90

Thus percentage purity of impure sample = 90