Chemistry

A compound A consists of 4.8% carbon and 95.2% bromine by mass. Its vapour density is 252. Find its :
(i) empirical formula
(ii) molecular formula

5 Likes

Element	% composition	Atomic weight	Relative no. of atoms	Simplest ratio
Carbon	4.8	12	$\dfrac{4.8}{12}$ = 0.4	$\dfrac{0.4}{0.4}$ = 1
Bromine	95.2	80	$\dfrac{95.2}{80 }$ = 1.19	$\dfrac{1.19}{0.4}$ = 2.9=3

Simplest ratio of whole numbers = C : Br = 1 : 3

Hence, empirical formula is CBr₃

(i) Empirical formula weight = 12 + 3(80) = 252 g

Molecular weight = 2 x V.D. = 2 x 252 = 504

$\text{n} = \dfrac{\text{Molecular weight}}{\text{Empirical formula weight}} \\[0.5em] = \dfrac{504}{252} = 2$

Molecular formula = n[E.F.] = 2[CBr₃] = C₂Br₆

∴ Molecular formula = C₂Br₆

Answered By

3 Likes