JAMB - Chemistry (2014 - No. 39)

A hydrocarbon has an empirical formula CH and a vapour density of 39. Determine its molecular formula.

[C = 12, H = 1]
C2H6
C3H8
C3H4
C6H6

Explanation

molecular mass = 2 x vapour density
= 2 x 39 = 79
∴ Cn Hn = 78
12n + 1n = 78
13n = 78
n = \(\frac{78}{13}\) = 6
∴ Cn Hn = C 6H 6

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