Chemistry -chemical formula and equations

Here's how you would go through such a combustion analysis question:

The combustion is centered around this reaction: CxHy + O2 --> CO2 + H2O

Using the molar mass of CO2, find the percentage of carbon in each molecule of CO2. You would do this by dividing the molar mass of carbon from the molar mass of CO2. Then, take that percentage and find the mass of carbon in the 2.933 g of CO2. The mass of the carbon divided by the 18.1 g of the total mass would give you the answer for 1). 

Do the same as above for H2O and hydrogen to answer 2). 

In terms of the empirical formula, use the mass of C and H calculated in 1) and 2) to find the moles of each by using mole ratios. Then, divide each quantity of moles you find by the lowest quantity calculated, which will yield the coefficients for the empirical formula in 3).  

To answer 4), the molar mass is given as 30. Find the molar mass of the empirical compound you found in 3) and divide it into the molar mass 30, to find the value that you would multiply all the coefficients by to yield the molecular formula.