If you wish to obtain 4.20 g of copper metal from copper(II) sulfide, what mass of (in grams) must you use?

Answer 1

Copper(II) sulfide = CuS

From this formula, you see that 1 mol of CuS contains 1 mol of copper (Cu).

How many moles of Cu are in 4.20 g of Cu?

4.20 g Cu x 1 mol Cu/63.5 g = 0.0661 moles

Molar mass CuS = 95.1 g/mol

0.0661 mol Cu x 1 mol CuS/mol Cu x 95.1 g/mol = 6.29 g CuS must be used