\"Native,\" or elemental copper can be found in nature, but most copper is mined

Question

"Native," or elemental copper can be found in nature, but most copper is mined as oxide or sulfide minerals. Chalcopyrite (CuFeS2) is one copper mineral that can be converted to elemental copper in a series of chemical steps. Reacting chalcopyrite with oxygen at high temperature produces a mixture of copper sulfide and iron oxide. The iron oxide is separated from CuS by reaction with sand (SiO2). CuS is converted to Cu2S in the process and the Cu2S is burned in air to produce Cu and SO2: 2CuFeS2+3O2rightarrow.png2CuS+2FeO+2SO2 2FeO+2SiO2rightarrow.png2FeSiO3 2CuSrightarrow.pngCu2S+S Cu2S+S+2O2rightarrow.png2Cu+2SO2

Part 2

How much chalcopyrite had to be mined to produce 100 penies if reaction 1 had a percent yield of 78.00% and all other reaction step had yields of 100%.

g CuFeS2

Part 3

How much chalcopyrite had be mined to produce 100 pennies if each reaction involving copper proceeded in 78.00% yield?

g CuFeS2

Explanation / Answer

Reactions are:

2 CuFeS2+ 3 O2 ===== 2CuS + 2FeO + 2SO2

2FeO+2SiO2 ======= 2FeSiO3

2CuS ====== Cu2S + S

Cu2S+S+2O2 ====== 2Cu + 2SO2

pennies are made of pure copper so

from the reaction we can see that 2 moles of chalcopyrite produce 2 moles of copper so

1 penny has a mass of 3 grams so 100 pennies have a mass of 300 grams

molar mass of copper = 63.55 g / mol

moles = 300 / 63.55 = 4.72 moles of copper

theoretically you should need 1 mole of chalcopyrite for every mole of copper you dont have a 100 percent yield you have 78% so the moles you need of chalcopyrite are

4.72 / 0.78 = 6.051 moles of chalcopyrite are needed

molar mass of chalcopyrite is 183.5 g / mol

so we know that moles = mass / molar mass so

mass = moles * molar mass = 183.5 * 6.051 = 1110.3585 grams of chalcopyrite

Part 3

For the last reaction we need 4.72 moles of Cu

1 mole of CU2S produces 2 moles of Cu so

4.72 / 2 = 2.36 moles of Cu2S

divide this by 0.78 to get = 3.025 moles of Cu2S

the second reaction

2 mole of CuS produces 1 mole of Cu2S so

3.025 * 2 = 6.05 moles of CuS

divide this by 0.78 to get

6.05 / 0.78 = 7.756 moles of CuS are required

2 moles of chalcopyrite requires 2 moles of CuS so just divide the last value by 0.78 to get

7.756 / 0.78 = 9.945 moles of chalcopyrite are required

apply

mass = moles * molar mass = 9.945 * 183.5 = 1824.90 grams of Chalcopyrite

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