Precipitation Reaction?

Question

A silver-copper alloy has a mass of 0.1264 g. When the alloy is dissolved in nitric acid the silver precipitates as silver chloride. The precipitate has a mass of .1375 g. What is the percent of silver in the alloy?

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Answer 1

rmm of AgCl = 107.87 g/mol +  35.45 g/mol = 143.32 g /mol.

0.1375/143.32 = 9.594 x10-4 moles of AgCl

Same for Ag: 9.594 x10-4 moles of Ag

Mass of Ag: 9.594 x10-4 x 107.87 = 0.1035 g of Ag

Per cent Ag: 0.1035/0.1264 = 0.8187 = 81.9%