text: Gimme a minute...\n\nFirst guess is 0.1195 moles of Carbon.\n\nHow? Since you got 5.256 g of CO2, if you divide that with the molecular mass of CO2 you'll get the moles of CO2:\n\n5.256 g X (1 mole of CO2 / 44g of CO2) = 0.1195 moles of CO2\n\n[  44 from C (12g/mole) and O2(2 x 16g/mole)  ]\n\nfrom 0.1195 moles of CO2 multiply that with (1 mole of Carbon per 1 mole of Carbon Dioxide CO2) which makes the number of moles of CO2 = to the number of moles of Carbon. Not a single molecule of Carbon is wasted, so I guess it's safe to assume that's also the number of moles of Carbon in the reactants.