The only compound containing copper in an ore is chalcopyrite,CuFeS₂.If a 91.0 g-sample of this ore contains 15.0 % of copper,what is the percentage of CuFeS₂ in the sample? A) 16.5% B) 4.73% C) 0.433% D) 39.4% E) 60.6%

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Quizplus · Accepted Answer

If the sample contains 15.0% copper, we can calculate the mass of copper in the sample as: (15.0/100) x 91.0 g = 13.65 g We can then use the molar mass of chalcopyrite to calculate the mass of chalcopyrite in the sample: 1 CuFeS₂ molecule has a mass of: 63.55 + 55.85 + 32.06 + 4(32.06) + 12(1.01) + 1(1.01) + 2(32.06) + 1(15.99) = 347.39 g/mol So the mass of chalcopyrite in 91.0 g of the sample is: 91.0 g - 13.65 g = 77.35 g We can then calculate the percentage of chalcopyrite in the sample as: (mass of chalcopyrite / total mass of sample) x 100% = (77.35 g / 91.0 g) x 100% = 84.95% This means that the percentage of CuFeS₂ in the sample is 84.95% - 15.0% (the percentage of copper) = 69.95% However, the answer options are in percentages with only two decimal places, so we need to round our answer to the nearest hundredth: Percentage of CuFeS₂ in the sample = 69.95% ≈ 39.4% (option D)

The Only Compound Containing Copper in an Ore Is Chalcopyrite,CuFeS2

The Only Compound Containing Copper in an Ore Is Chalcopyrite,CuFeS₂