the equation for the combustion reaction is as follows
CₐHₓ + O₂ ---> CO₂ + H₂O
the coefficients for the compounds are unknown as we dont know the formula of the hydrocarbon yet
the number of moles of CO₂ formed is - 17.3 g / 44 g/mol = 0.39 mol
number of moles of H₂O formed - 8.83 g / 18 g/mol = 0.49 mol
next we have to find the number of moles of C and H present to find the empirical formula of the hydrocarbon
1 mol of CO₂ contains - 1 mol of C
therefore 0.39 mol of CO₂ contains - 0.39 mol of C
1 mol of H₂O contains - 2 mol of H
therefore 0.49 mol of H₂O contains - 2 x 0.49 = 0.98 mol of H
C H
number of moles - 0.39 mol 0.98 mol
divide both by the lesser number of moles
0.39 / 0.39 = 1 0.98 / 0.39 = 2.5
since 2.5 cannot be rounded off we multiply both by 2 to get a number that can be rounded off to a whole number
C - 1 x 2 = 2
H - 2.5 x 2 = 5
therefore empirical formula is C₂H₅