Question

A 10.0 SAMPLE OF A MIXTURE OF CALCIUM CHLORIDE AND SODIUM CHLORIDE IS TREATED WITH SODIUM CARBONATE TO PRECIPITATETHE CALCIUM AS CALCIUM CORBONATE .THIS CALCIUM CARBONATE IS HEATED TO CONVERT ALL THE CALIUM TO CALCIUM OXIDE AND THE FINAL MASS OF CALICUM OXIDE IS 1.62 GRAMS .THE % BY MASS OF CALCIUM CHLORIDE IN THE ORIGINAL MIXTURE IS?

Answer 1

The reactions are:
CaCl₂ + Na₂CO₃ $\to$ CaCO₃ + 2NaCl
CaCO₃ $\to$ CaO + CO₂

1 mole of CaO is formed from 1 mole CaCO₃
1mole of CaCO₃ is formed from 1 mole of CaCl₂
Mole ratio of CaO to CaCl₂ is 1: 1
Moles of CaO formed = mass/molar mass = 1.62/56=0.0289mol
Moles of CaCl₂ = 0.0289mol
Mass of CaCl₂ = 0.0289 $\times$ 111 = 3.2079g
The total mass of the mixture of calcium chloride and sodium chloride in the question is mentioned as 10 and assuming that it is 10g,
% mass of CaCl₂ in the original mixture is $\frac{3.2079\times 100}{10}$ = 32.079 % or 32.08%