Copper Mineralsa % composition exercise

Simple Copper Sulfides

Chalcocite: copper (I) sulfide

Tenorite:

copper (II) sulfide

1. Write the formulas for each sulfide and determine the %Cu.

Complex Copper Sulfides

Bornite Cu5FeS4

Chalcopyrite CuFeS2

2. From inspection (by looking), which ore has the highest %Cu? Calculate the %Cu in each to see if you’re right!

Semiprecious Copper Gems

Malachite

CuCO3.Cu(OH)2

Azurite 2CuCO3.Cu(OH)2

3a. Determine the %Cu in each gem.

3b. Which contains more copper: 10.0 g of azurite or 9.00 g of malachite?

Cuprite: copper (I) oxide

single crystal

more usual form (microcrystalline)

4a. Find the %Cu in cuprite.

4b. How many Cu atoms are there in a 5.25 g crystal of cuprite?

4c. If a sample contained 0.30 moles of Cu atoms, how many moles of oxygen atoms would it have?

While most copper compounds are blues or greens, there is one red one.

Answer Key1. copper (I) sulfide = Cu2S; copper (II) sulfide = CuS

% Cu in Cu2S = {(2*63.5 g)/[(2*63.5 g)+32.1 g]}*100 = 79.8%

% Cu in CuS = [(63.5 g)/(63.5 +32.1 g)]*100 = 66.4%

2. With 5 Cu, bornite looks to have a higher %Cu than chalcopyrite with one Cu.

bornite = 63.3% Cu

chalcopyrite = 34.6% Cu

3a. azurite (3Cu, 8O, 2H, 2C)= 55.3% Cu

malachite (2Cu, 1C, 5O, 2H) = 57.5% Cu

3b. 10.0 g azurite * 0.553 = 5.53 g Cu

9.00 g malachite *0.575 = 5.18 g Cu, so AZURITE HAS MORE Cu

4a. copper (I) oxide = Cu2O; cuprite = 88.8% Cu

4b. 5.25 g sample* 0.888 = 4.66 g Cu

4.66 g Cu * (1 mole/63.5 g) * (6.02 x 1023 atoms/1 mole) = 4.42 x 1022 atoms

4c. Cu2O has one oxygen for every 2 copper atoms, so a sample with 0.30 mol. Cu would have (1/2)(0.30 mol) = 0.15 moles oxygen