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Bugbaja Bugbaja
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11 years ago
If 4.32-g Cu combines with 1.09-g of sulfur to form 5.42 g of the bluish-black mineral chalcocite, what is the empirical formula and the percent by mass of copper in chalcocite?

What is the empirical formula?
Percent by mass is _____ % copper (don't forget to check significant figures)
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wrote...
#1
11 years ago
google it
wrote...
#2
11 years ago
First, find the moles of each element:

For Cu: 4.32g/63.5g/mole = 0.0680 mole
For S: 1.09g/32.06g/mole = 0.0340 mole

Looks like 2 Cu's to one S or Cu2S

Percent Cu would be:

4.32/(4.32 + 1.09) = 79.9% Cu
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