Question

Pure copper may be produced by the reaction of copper(I) sulfide with oxygen gas as follows:

Cu₂S(s) + O₂(g) → 2Cu(s) + SO₂(g)

If 0.490 kg of copper(I) sulfide reacts with excess oxygen, what mass of copper metal may be produced?

	A.	0.980 kg
	B.	0.490 kg
	C.	0.391 kg
	D.	0.196 kg
	E.	0.0978 kg

Answer 1

Molar mass of Cu2S = 159 g/mol
mass of Cu2S = 0.49 Kg = 0.49*1000 = 490g

number of moles of Cu2S = mass/molar mass
                                      = 490/159
                                      = 3.08 mol

1 mol of Cu2S gives 2moles of Cu
so,
number of moles of Cu formed = 2*3.08 mol = 6.16mol

Molar mass of Cu = 63.5 g/mol

Mass of Cu = molar mass * number of moles
                 = 63.5 * 6.16
                 = 391 g
                 = 0.391 Kg
Answer: 0.391 Kg