Question

Four cylinders are filled with 11.2 L of ${\text{H}}_2$, 5 L of ${\text{O}}_2$, 22.4 L of ${\text{N}}_2$ and 8 L of ${\text{Cl}}_2$ gases. Which cylinder contains the maximum number of molecules at STP?

• A. The cylinder containing hydrogen.
• B. The cylinder containing oxygen.
• C. The cylinder containing nitrogen.
• D. The cylinder containing nitrogen chlorine.

Answer 1

The correct option is C The cylinder containing nitrogen.

Volume of ${\text{H}}_2$ gas = 11.2 L
Volume of ${\text{O}}_2$ gas = 5 L
Volume of ${\text{N}}_2$ gas = 22.4 L
Volume of ${\text{Cl}}_2$ gas = 8 L

We kow that, molar volume of any gas at STP (litres) = 22.4 L
In case of gases at STP,
Number of molecules = $\frac{\text{Volume of gas}}{\text{Molar volume}}\times \text{Avogadro Number}$
$=\text{Number of moles}\times AvogadroNumber$

So, the number of molecules is directly proportional to the number of moles.

Number of moles of hydrogen = $\frac{11.2}{22.4}$ = 0.50
Number of moles of oxygen = $\frac{5}{22.4}$ = 0.22
Number of moles of nitrogen = $\frac{22.4}{22.4}$ = 1.00
Number of moles of chlorine = $\frac{8}{22.4}$ = 0.36.
The cylinder containing nitrogen will have maximum number of moles. Hence, that cylinder contains the maximum number of molecules.