GATE 2026 MT – Question 62
A copper ore contains 30 wt.% chalcopyrite ($\mathrm{CuFeS_2}$) and the remaining gangue has no copper. The copper content of the ore is ________ wt.%. (Rounded off to one decimal place.) Given atomic weights: Fe = 56, Cu = 63.5, and S = 32 g/mol.
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Correct answer: 10.3 to 10.5
Explanation
The formula mass of chalcopyrite is $63.5+56+2(32)=183.5\ \mathrm{g/mol}$. Its copper mass fraction is $63.5/183.5$.
Only 30% of the ore is chalcopyrite, so the copper content is $30(63.5/183.5)=10.3815$ wt.%. Enter **10.4 wt.%**.