Copper Minerals a % 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 Cu 5 FeS 4 Chalcopyrite CuFeS 2 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 CuCO 3. Cu(OH) 2 Azurite 2CuCO 3. 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 Key 1.copper (I) sulfide = Cu 2 S; copper (II) sulfide = CuS % Cu in Cu 2 S = {(2*63.5 g)/[(2*63.5 g)+32.1 g]}*100 = 79.8% % Cu in CuS = [(63.5 g)/( 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 g azurite * = 5.53 g Cu 9.00 g malachite *0.575 = 5.18 g Cu, so AZURITE HAS MORE Cu 4a. copper (I) oxide = Cu 2 O; cuprite = 88.8% Cu 4b g sample* = 4.66 g Cu 4.66 g Cu * (1 mole/63.5 g) * (6.02 x atoms/1 mole) = 4.42 x atoms 4c. Cu 2 O 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