Question

The most common source of copper (Cu) is the mineral chalcopyrite (CuFeS2). How many kilograms of chalcopyrite must be mined to obtain 200.5 g of pure Cu?Express your answer to three significant figures and include the appropriate units

Answer 1

We have to obtain 200.5 g of pure Cu. We have to convert that value into moles. To do that we will use the molar mass of Cu.

molar mass of Cu = 63.55 g/mol

moles of Cu = mass of Cu/molar mass of Cu

moles of Cu = 200.5 g/(63.55 g/mol)

moles of Cu = 3.155 moles

So we want to mine 200.5 g of pure Cu or 3.155 moles of Cu.

One molecule of the mineral chalcopyrite (CuFeS₂) contains one atom of Cu, one atom of Fe and 2 atoms of Fe. So, 1 mol of CuFeS₂ contains 1 mol of Cu atoms. Or, if we want to obtain 1 mol of Cu atoms we have to mine 1 mol of CuFeS₂. We will use that conversion to get the number of moles of CuFeS₂ that we have to mine to get 3.155 moles of pure Cu.

1 mol of CuFeS₂ = 1 mol of Cu

moles of CuFeS₂ = 3.155 moles of Cu * 1 mol of CuFeS₂/(1 mol of Cu)

moles of CuFeS₂ = 3.155 moles

If we want to get 3.155 moles of pure Cu, we have to mine 3.155 moles of CuFeS₂. Finally we can convert those moles into grams using the molar mass of CuFeS₂ and then convert it to kg.

atomic mass of Cu = 63.55 amu

atomic mass of Fe = 55.85 amu

atomic mass of S = 32.07 amu

molar mass of CuFeS₂ = 63.55 + 55.85 + 32.07 * 2

molar mass of CuFeS₂ = 183.54 g/mol

mass of CuFeS₂ = moles of CuFeS₂ * molar mass of CuFeS₂

mass of CuFeS₂ = 3.155 moles * 183.54 g/mol

mass of CuFeS₂ = 579 g

1000 g = 1 kg

mass of CuFeS₂ = 579 g = 579 g * 1 kg/(1000 g)

mass of CuFeS₂ = 0.579 kg

Answer: We have to mine 0.579 kg of chalcopyrite to obtain 200.5 g of pure Cu.