One mole of a hydrocarbon contains 36g of carbon and its vapour density is 20. The structure of the hydrocarbon is?

A. CH3C ≡ CH
B. CH3CH = CH2
C. CH3CH2C ≡ CH
D. CH3CH2 CH3

Correct Answer:

Option A – CH3C ≡ CH

Explanation

2 X VD = Rmm VD = Vapour density; Rmm – Relative
2 X 20 = 40 Molecular mass
Mole of carbon = 36/12 = 3
Mole of H2 = 40 – 36 = 4

The compound contains 3 moles of carbon and 4 hydrogen