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Composition of Materials. Unit 2 Section C.4. % Composition. percent composition: (def) percent by mass of each material found in an item Percent composition helps geologists describe how much metal or mineral is present in a particular ore .
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Composition of Materials Unit 2Section C.4
% Composition • percent composition: (def) percent by mass of each material found in an item • Percent composition helps geologists describe how much metal or mineral is present in a particular ore. • They can evaluate if the metal should even be mined.
Common Copper-containing minerals • To calculate the % of Cu in each mineral: • mass of Cu in compound x 100 total mass of compound • Cu2S mass of Cu in compound: 63.55g x 2 = 127.1 g Cu total mass of compound: (63.55 g x 2) + 32.07 g = 159.17 g % Cu = (127.1g/159.17g) x 100 = 79.85% Cu
Copper-containing minerals • CuFeS2 mass Cu: 63.55 g mass of compound: 63.55 g + 55.85 g + (32.07g x 2) = 183.54 g %Cu = 63.55 g Cu x 100 = 34.62% Cu 183.54 g compound
Copper-Containing minerals • Cu2CO3(OH)2 mass Cu in compound: 63.55 g x 2 = 127.1 g Cu total mass of compound (63.55 g x 2) 12.01g (16.00g x 3) %Cu = 127.1 g Cu = 57.48% (16.00g x 2) 221.13 g total + (1.01 g x 2) 221.13 g
Mining a Metal Ore • Two factors to consider when deciding whether it’s worthwhile to mine a particular ore: 1) percent of mineral in the ore 2) percent of metal in the mineral
Picture to Relate % Metal in Ore Amount of Cu in ore containing 10% chalcocite (Cu2S)
Percent Comp. Practice • Ag2S • Al2O3
Practice Problems • CaCO3
Practice Problems • A 50.0-gram sample of ore contains 5.00g of lead(III)sulfate, PbSO4 • a) What is the % metal in PbSO4? • b) What is the percent PbSO4 in the ore?
Practice Problems • A 50.0-gram sample of ore contains 5.00g of lead(III)sulfate, PbSO4 • c) What is the percent Pb in the total ore sample?
Practice Problems • Which mineral would be most profitable to mine for chromium? • FeCr2O4, PbCrO4, or Cr2O3