Question

If air contains nitrogen and oxygen gases in the volume ratio $4:1$. The vapour density of air is:

• A. $14.4$
• B. $15$
• C. $16.5$
• D. $18$

Answer 1

The correct option is A $14.4$

Volume ratio $=$ mole ratio $=4:1$

$\therefore x_{N_2}=\frac{4}{5},x_{O_2}=\frac{1}{5}$

$Mw$ of air $=\frac{4}{5}\times 28+\frac{1}{5}\times 32=28.8$

$Vapor$ $density=\frac{molecularweight}{2}=\frac{28.8}{2}=14.4$