[govibe]

OK, these two things are getting me mixed up... Our teacher taught us that we can use the percent composition of a compound to figure out how much of a specific element in that compound is produced. For example, if we know 5 g of CO2 is produced, we can use the percent composition to figure out how much Carbon is produced...

Then there is another way to calculate such things... I was also taught that if we know one mole of CO2 is produced, we know that one mole of C and 2 moles of Oxygen are produced... Are these two methods essentially the same? when would you use each one?

[Bakegaku]

When one mole of Carbon dioxide is produced, one mole of carbon (atoms) and two moles of oxygen are used.  Is that what you mean?

[Yggdrasil]

If you know the mass of carbon dioxide produced, you can use the percent composition to tell you the grams of carbon produced.  Example, carbon dioxide is 27.3% carbon by mass.  Therefore, 1 g of carbon dioxide contains 0.273g of carbon.

If you know the number of moles of carbon dioxide produced, you can use the molecular formula to tell you the grams of carbon.  For example, carbon dioxide is CO₂.  That means one mole of carbon dioxide will contain one mole of carbon atoms and two moles of oxygen atoms.