A greenish blue salt known to be composed of copper and chloride ions is dissolved in DI water. Aluminum metal is used to reduce the copper ions to metallic copper, which is collected, dried and weighed. If the origanal sample has a mass 1.362g and the collected copper has a mass .635g, what is the empirical formula of bthe compound?

1 answer

CuClx + Al ==> Cu +_ AlClx (not balanced)
mass CuClx = 1.362
-mass Cu = 0.635
------------------
mass Cl = 0.727

mols Cu = 0.635/63.5 = about 0.01
mols Cl = 0.727/35.5 = about 0.02

Find the ratio of Cu to Cl and write as the empirical formula. If you don't see that immediately, divide both numbers by the same small number to get whole numbers.