[Korokian]

A 1.25-g sample of a compound containing only C,H, and O is analyzed by complete combustion of CO₂ and H₂O and is found to form 1.45g of CO₂ and 0.592g H₂O.  Find the empirical formula of the compound.  In a seperate measurement the molecular weight is found to be 153.  Find the molecular formula of the compound. 
A) amount of C in sample_____
B) amount of H in sampe______
C) mass of O in sample_______
D) amount of O in sample_______
E) emperical formula_______
F) molecular formula_______

can i get a clue on where to start please?
C_xH_yO_z + O₂ ------> CO₂ + H₂O
do i use the mass composition formula for C?

[sdekivit]

Hint:

when you have CxHyOz is completely combusted to H2O and CO2, all the C from CxHyOZ ends up in CO2 and all H ends up as H2O.

--> so when you know the mass of CO2 and H2O formed, you also know the amount of mol C and H in CxHyOz and all the rest of mass will be O in CxHyOz.

[Korokian]

so i converted 1.45 g CO2 to 0.033 mol CO2
and 0.529g H2O to .033 mol H2O
so is it .0329 mol C
and .0329 mol H2?

[Dan]

Yes.

[Korokian]

how do you get the mass of the O?

[BaO]

there is a previous post related to your question: http://www.chemicalforums.com/index.php?topic=10022.msg47591#msg47591
 i think it will help you figure it out.

[Korokian]

GOT IT TY