Question

Given atomic weights of Cu, Fe and S as 63.55, 55.85 and 32.10, respectively, find out the weight of copper (in gram) metal in an ore (no associated gangue) of 1kg weight constituting of bornite, chalcopyrite and chalcocite present in weight fractions of 0.4, 0.4 and 0.2, respectively.
(Round off to one decimal place)

Answer 1

Correct Answer: 550

To solve the problem, we need to calculate the weight of copper in a 1 kg ore sample containing bornite, chalcopyrite, and chalcocite. Let's break down the solution:

• Chemical formulae:
  • Bornite (Cu₅FeS₄)
  • Chalcopyrite (CuFeS₂)
  • Chalcocite (Cu₂S)
• Molar masses:
  • Bornite = 5×63.55 + 55.85 + 4×32.10 = 501.1 g/mol
  • Chalcopyrite = 63.55 + 55.85 + 2×32.10 = 183.6 g/mol
  • Chalcocite = 2×63.55 + 32.10 = 159.2 g/mol
• Weight of copper per mineral:
  • Bornite has 5 Cu atoms: (5×63.55)/501.1 = 0.634
  • Chalcopyrite has 1 Cu atom: 63.55/183.6 = 0.346
  • Chalcocite has 2 Cu atoms: (2×63.55)/159.2 = 0.798
• Total copper weight in ore:
  • Bornite part: 0.4 kg; Cu = 0.4 × 0.634 × 1000 = 253.6 g
  • Chalcopyrite part: 0.4 kg; Cu = 0.4 × 0.346 × 1000 = 138.4 g
  • Chalcocite part: 0.2 kg; Cu = 0.2 × 0.798 × 1000 = 159.6 g
• Total copper in 1 kg ore: 253.6 + 138.4 + 159.6 = 551.6 g
• Final weight after rounding: 551.6 g