Question

A 12.42 gram sample of a mixture of NaCl and CaCl2 is dissolved in water and all the chloride is precipitated as AgCl. If the AgCl precipitate has a mass of 31.70 grams. How do I find the mass percentage of each component in the original mixture?

Answer 1

You write two equations and solve them simultaneously. First equation is
let x = mass NaCl
and y = mass CaCl2
----------------------
equation 1 is
x + y = 12.42

The second equation you get by converting x and y to grams AgCl
For NaCl(x) that is
x(mm AgCl/mm NaCl) where mm is molar mass.

For CaCl2(y) that is
y(mm CaCl2/2*mm AgCl)

and you know total mass of AgCl is 31.70 so
x(mm NaCl/mm AgCl) + y(mm CaCl2/2*mm AgCl = 31.70 g

Solve for x and y, then
% NaCl = (x/12.42)*100 = ?
% CaCl2 = (y/12.42)*100 = ?

Post your work if you get stuck.