Q:- An impure sample of NaCl, which weighed 0.50 g, gave on treatment with excess of AgNO

_{3} solution, 0.90 g of AgCl as precipitate. Calculate the percentage purity of the sample.

Reaction: NaCl + AgNO

_{3} NaNO

_{3} + AgCl

The formula for percentage purity is : (Pure/Total wt.) * 100

Is this correct?

My attempt to the solution: 143.5 g of AgCl will be given by = 58.5 g of pure NaCl

Therefore, 0.9 g of Agcl will be given by = (58.5/143.5)*0.9 = 0.36 g of pure NaCl

We have 0.36 g pure NaCl(by calculation) and total wt. = 0.50 g.

Therefore, percentage purity= (0.36/0.50)*100 = 72 %

But it is incorrect. The correct answer is 73.4 %