Question

A compound has the empirical formula $ CH_{2}O $ . Its vapour density is $30$. Its molecular formula is

• A. $C _{2} H _{4} O _{2}$
• B. $C _{2} H _{6} O$
• C. $C _{2} H _{6} O _{2}$
• D. $C _{2} H _{4} O$

Answer 1

Answer: (A)

$2 \times$ vapour density $=$ molecular weight $2 \times 30=60$
$\therefore $ Molecular weight of compound $=60$ (Empirical formula) $\times n=$ molecular formula
$(12+1 \times 2+16) \times n=60$
$\therefore n=2$ so, $\left( CH _{2} O \right) \times 2=$ molecular formula
$\therefore $ Molecular formula $= C _{2} H _{4} O _{2}$