A gaseous hydrocarbon weights 0.70 g. and contains 0.60 g. of carbon. Find the molecular formula of the compound if it’s molecular weight is 70. [C = 12, H = 1]

H = 0.70 – 0.60 = 0.1 g

Simplest ratio of whole numbers = C : H = 1 : 2

Hence, empirical formula is CH₂

Empirical formula weight = 12 + 2(1) = 14

Molecular weight = 70

n = $Molecular\ weight\over Emperical\ Formula\ Weight$

= $70\over 14$ = 5

Molecular formula = (CH₂)₅ = C₅H₁₀

Hence, Molecular formula = C₅H₁₀