An unknown compound contains only carbon, hydrogen, and oxygen (cxhyoz). combustion of 6.00 g of this compound produced 8.80 g of carbon dioxide and 3.60 g of water. part a how many moles of carbon, c, were in the original sample?

When we have CO2 = 8.89 & H2O = 3.6 g & the total compound = 6 g So by using the molar mass of C we can get the grams of substance:
For carbon = 8.89 g (CO2)  * 12 g/mol (C)  / 44 CO2 = 2.4 g C
and then we get the moles by using the molar mass of C :
Mol of C = 2.4 g (C) * 12 g/mol = 0.2 mol C