Question

If equal masses of oxygen and nitrogen are placed in separate containers of equal volume at the same temperature, which one of the following statements is true?
$[MW$ of $N_2=28,O_2=32]$.

• A. Both flasks contain the same number of molecules
• B. The pressure in the nitrogen flask is greater than in the oxygen flask
• C. More molecules are present in the oxygen flask
• D. Molecules in the oxygen flask are moving faster on the average than the ones in the nitrogen flask

Answer 1

The correct option is B The pressure in the nitrogen flask is greater than in the oxygen flask

The ideal gas equation is $PV=nRT=\frac{m}{M}RT$.

Here, m is the mass and M is the molecular weight.

For oxygen and nitrogen, the volume, mass and temperature are the same.

Hence their pressures are inversely proportional to their molecular weights.

The molecular weight of nitrogen (28) is smaller than that of oxygen (32).

Hence, the pressure in the nitrogen flask is greater than in the oxygen flask.

Hence, the correct answer is option $\text{B}$.