Question

The molecular formula of a gas with vapour density 15 and empirical formula $C{H}_3$ is :

• A. $C_2{H}_6$
• B. $C_3{H}_8$
• C. $C_4{H}_{10}$
• D. $C{H}_3$

Answer 1

The correct option is A $C_2{H}_6$

As we know,
Molecular weight $=$ Vapour density $\times 2=2\times 15=30$
Molecular formula $=$ Empirical formula $\times$ n

$n=\frac{Molecularweight}{Empiricalformulaweight}=30/15=2$

so molecular formula $2\times \left(C{H}_3\right)=C_2{H}_6$