Question

A compound X consists fo 4.8 % carbon and 95.2 % bromine by mass:
(i) Determine the empirical formula of this compound working correctly to one decimal place (C = 12; Br = 80).
(ii) If the vapour density of the compound is 252, what is the molecular formula of the compound?

Answer 1

i) Calculation of Empirical formula

Element	%age	Relative No. of atoms	Simple
carbon	4.8	$\frac{4.8}{12}=0.4$	$\frac{0.4}{0.4}=1$
Bromine	95.2	$\frac{95.2}{80}=1.2$	$\frac{1.2}{0.4}=3$

Empirical Formula =
ii) Relative molecular mass = VD $\times$ 2
= 252$\times$ 2 = 504
Empirical Mass = 12 + 80 $\times$ 3 = 252
n=
Molecular fomula =()2
=