Answer to Question #2631 in Organic Chemistry for ashley

Question

A 2.007 gram sample of a hydrocarbon is combusted to give 1.389 grams of H[sub]2[/sub]O and 6.785 grams of CO[sub]2[/sub]. What is the empirical formula of the compund?

Answer 1

C_nH_m + xO₂ = nCO₂ + m/2H₂O

2.007 g 6.785 g 1.389 g


n(H₂O) = 1.389/18 = 0.0771mole
n(CO₂) = 6.785/44 = 0.1542mole
n/m = n(CO₂)/(2*n(H₂O)) = 2 therefore it is alkene C_nH_2n
We cannot say more, because carbon- hydrogenatoms ratio is constant.