C hemistry
posted by isoka .
An unknown compound contains only carbon, hydrogen, and oxygen . Combustion of 2.50 g of this compound produced 3.67 g of carbon dioxide and 1.50 g of water.
What is the empirical formula of a substance that contains 8.33×10−2 mol of carbon, 0.167 mol of hydrogen, and 8.32×10−2 mol of oxygen?

Are there two problems here.
#1.
Convert 3.67 g CO2 to g C, then divide by 2.50 to obtain %C.
Convert 1.50 g H2O to grams H and divide by 2.50 to convert to %H (after multiplying by 100, of course).
Now take a 100 g sample which gives you the percents in grams, convert g C to moles C, convert g H to moles H.
To find O, add percent C and percent H and subtract from 100 nd convert g O to moles.
Then find the whole number ratios of C, H, and O to each other with the smallest number being no less than 1.
Post your work if you get stuck. 
sorry just this one
What is the empirical formula of a substance that contains 8.33×10−2 mol of carbon, 0.167 mol of hydrogen, and 8.32×10−2 mol of oxygen? 
Most of the work is done since you already have C, H, and O in the form of moles. Divide by the smallest number (so that the smallest number ratio will be 1.000), then divide the other numbers by the same small number. See if you get CH2O? That's what I have.