Question

Empirical formula of a compound is $CH_{2}O$ and its vapour density is 30. Molecular formula of the compound is

• A. $C_{2}H_{6}O_{3}$
• B. $C_{2}H_{4}O_{2}$
• C. $C_{2}H_{4}O$
• D. $CH_{2}O$

Answer 1

Answer: (B)

Empirical formula $= CH_{2}O$
Empirical formula mass $=12 + 2+16 = 30$
Mol. mass $=2 \times V.D. =2 \times 30=60$
$n=\frac{\text{Mol. mass}}{\text{Empencal mass}}$
$=\frac{60}{32}=2$
Molecular formula $={\text{ (emperical formula)}}_{n}$
$=(CH_{2}O)_{2} =C_{2}H_{4}O_{2}$