A hydrocarbon has an empirical formula CH and a vapour density of 39. Determine its molecular formula. [C = 12, H = 1]

A. C2H6
B. C3H8
C. C3H4
D. C6H6

Correct Answer:

Option D = C6H6

Explanation

molecular mass = 2 x vapour density
= 2 x 39 = 79
∴ CnHn = 78
12n + 1n = 78
13n = 78
n = 78/13
= 6
∴ CnHn = C6H6