Question

a sample of copper wire with a mass of 1.659 g is heated with excess powdered sulfur until the copper has combined with the sulfur, and all the extra sulfur has been burned off. The final product (a sulfide of copper) has a mass of 2.080 g. Calculate the empirical formula of the product, and name it.

Answer 1

First you figure out how many grams of sulfur has been used.
2.080g - 1.659g = 0.421g of S used
Now change all of your grams to mols.
1.659g of Cu / 63.546g/mol = 0.02611mol of Cu
0.421g of S / 32.065g/mol = 0.01313 mol of S
From this you can see that S has less so we divide both numbers by the number of moles of S so we can get a ratio of S to Cu.
0.01313/0.01313 = 1 for S
0.02611/0.01313 = 2 for Cu
So the empirical formula would be Cu2S or copper sulfide.