Question

The ratio of masses of oxygen and nitrogen in a particular gaseous mixture is 1 : 4. The ratio of number of their molecules is:

• A. 1 : 4
• B. 7 : 32
• C. 1 : 8
• D. 3 : 16

Answer 1

Answer: (B)

Let the mass of oxygen be $x$ gm
$\therefore$ Mass of nitrogen $=4xgm$
Number of molecules $=6.023\times 10^{23}\times$ number of moles
$\therefore \text{ Ratio }=\frac{6.023\times 10^{23}\times \text{ no. of moles of oxygen }}{6.023\times 10^{23}\times \text{ no. of moles of nitrogen }}$
$=\frac{\frac{m_{O_2}}{M_{O_2}}}{\frac{m_{N_2}}{M_{N_2}}}=\frac{\frac{x}{32}}{\frac{3x}{28}}$
$=\frac{7}{32}=7:32$