Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: johnnyjohn993 on October 06, 2014, 10:41:29 AM
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Bornite ( 2Cu3FeS3 )
2Cu3FeS3 + 7O2 :rarrow: 6Cu +2FeO + 6SO2
If 2.50 metric tons of bornite is reacted with excess O2 and the process has an 86.3% yield of copper , what mass of copper is produced?
MY SOLUTION:
I got 0.871 tons of O2 using the stoichiometric relation of bornite and Oxygen.
Then I used the amount of Oxygen (i.e 0.817 tons O2) to evaluate the the mass of Cu... (by means of stoichiometric relation again) and I got 1.39 tons of Cu.
Question : HOw do I use the 86.3 % yield of copper in getting the right answer.
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If there is an excess of oxygen it means all bornite reacted - and you don't have to calculate amount of oxygen. Also, you can calculate theoretical yield of copper directly from the given amount of bornite, not through the oxygen - while the final results are equivalent and shoudl be identical, you just did two times more work than necessary.
1.39 tons is a theoretical yield. Real yield is 86.3% of that. Just multiply.
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See also: http://en.wikipedia.org/wiki/Yield_(chemistry)