An average copper penny minted in the 1960s contained about 3.000 g of copper. how much chalcopyrite had be mined to produce 100 pennies?

To know the answer, determine first the mass of the copper used:

Copper used = 100 pennies x 3.0g Cu per penny = 300.0 g Cu 

then, determine the pathway and molar ratio from Cu formed back to CuFeS2 required using the balanced reactions:

1 Cu2S from 2 CuS; 2Cu from 1 Cu2S; 2CuS from 2CuFeS2 
Therefore 2Cu from 2CuFeS2, they are in a one to one molar ratio. 

then, convert g Cu to moles and g of CuFeS2:
= 300.0 g Cu * 1 mol Cu/63.546g Cu * 2 mol CuFeS2/2 moles Cu

= 4.72 moles CuFeS2 

chalcopyrite had to be mined = 4.72 moles CuFeS2 * 183.54 g CuFeS2/1 mole CuFeS2 = 866.49 g CuFeS2

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