Complete combustion of 5.70 g of a hydrocarbon produced 17.3 g of co2 and 8.83 g of h2o. what is the empirical formula for the hydrocarbon?

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

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