Question

A 24.42 g sample of a compound contains 7.79 g of potassium, K, 7.06 g of chlorine, Cl, and oxygen, O. Calculate the empirical formula.

Answer 1

Net weight of sample is 24.42 g . Weight of potassium is 7.79 g . Weight of chlorine is 7.06 g .

Thus, weight of oxygen is [24.42- (7.79+7.06)] = 9.57 g .

Now, molecular weight of potassium is 39.0983 . Thus , number of moles present in the compound is () = 0.199 0.2 .

Molecular weight of chlorine 35.453 . Thus, number of moles present in the compound is () = 0.199 0.2 .

Molecular weight of oxygen is 15.999 . Thus, number of moles present in the compound is () = 0.598 0.6 .

Thus, molar ratio of Potassium: Chlorine: Oxygen = 0.2 : 0.2 : 0.6 = 1:1:3 . Thus, emperical formula of the compound is KClO₃ .