What is the weight percent chloride in a sample?

Question

A sample containing potassium chloride and inert material was analyzed by the Mohr method. A portion of the solid weighing 0.2500 g was dissolved and titrated with 0.07575 M AgNO_3 solution to a brick-red silver chromate end point. If the titration consumed 43.22 mL of the AgNO_3 solution, what is the weight percent chloride (35.45 g/mol) in the sample? What is the weight percent KCl (74.55 g/mol) in the sample?

Answer 1

moles AgNO3 :

0.04322 litres @ 0.07575 mol/litre = 0.003274 moles AgNO3

since 1 mole Ag+ reacts with 1 mole Cl- :

0.003274 moles AgNO3 = 0.003274 moles Cl-

grams of chloride:

0.003274 moles Cl- @ 35,45 g/mol = 0.1161 grams of Cl-

% Cl- :

0.1161 grams Cl- / 0.2500 g sample (100) = 46.42 % Cl-

Your answer is 46.42% Cl-