posted by Jake .
A 0.887 g sample of a mixture of NaCl and KCl is dissolved in water and the solution is treated with an excess of AgNO3 producing 1.822 g of AgCl. What is the percent by mass of each component in the mixture?
Two equations and two unknowns.
mass NaCl + mass KCl = 0.887 g
I would let y = mass NaCl and z = mass KCl.
AgCl from NaCl + AgCl from KCl = 1.822 g.
y g*(1 mol AgCl/1 mol NaCl) + z g*(1 mol AgCl/1 mol KCl) = 1.822.
Solve for y and z
You want percent of each; therefore,
(grams y/mass sample)*100 = %NaCl
(grams z/mass sample)*100 = %KCl.
[Note:Mass of the sample is 0.877 in the problem.][another note: where 1 mol AgCl/1 mol NaCl is used, substitute molar mass AgCl and molar mass NaCl. For 1 mol AgCl/1 mol KCl substitute molar mass AgCl and molar mass KCl.]