Question

A gaseous hydrocarbon contains 85.7% Carbon and 14.3% Hydrogen.1 litre of the hydrocarbon weigh 1.26 g At NTP determine the molecular formulae of the hydrocarbon

Answer 1

Carbon : Hydrogen mole ratio = 85.7/12:14.3

= 7:14 = 1:2

Empirical formula = CH2: empirical formula wt = 14

Given 1 litre at ntp weighs 1.26 g

Therefore 22.4 litres will weigh 22.4 x 1.26 = 28 g

n = 28/14 = 2

Therefore formula of the hydrocarbon is C2H4 is ethylene.