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 ?(Mol wt. `N_2=28, O_2=32`)

Options

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

Explanation

To solve the problem, we need to analyze the conditions given and apply the ideal gas law and concepts of moles and molecular weight.

### Step-by-Step Solution:

1. **Understanding the Given Information**:
- We have equal masses of nitrogen (N₂) and oxygen (O₂) in separate containers.
- The containers have equal volume and are at the same temperature.
- Molecular weights: N₂ = 28 g/mol, O₂ = 32 g/mol.

2. **Calculating Moles of Each Gas**:
- Let the mass of each gas be `m` grams.
- The number of moles of nitrogen (N₂) can be calculated using the formula:
\[ \text{Moles of } N_2 = \frac{m}{28} \]
- The number of moles of oxygen (O₂) can be calculated using the formula:
\[ \text{Moles of } O_2 = \frac{m}{32} \]

3. **Comparing the Number of Moles**:
- Since both gases have the same mass `m`, we can compare the number of moles:
- Moles of N₂ > Moles of O₂ because \( \frac{m}{28} > \frac{m}{32} \).
- This implies that there are more moles (and thus more molecules) of nitrogen than oxygen in their respective containers.

4. **Applying the Ideal Gas Law**:
- According to the ideal gas law, \( PV = nRT \). Since volume (V) and temperature (T) are constant for both gases, the pressure (P) is directly proportional to the number of moles (n).
- Therefore, since there are more moles of nitrogen, the pressure in the nitrogen container will be greater than in the oxygen container.

5. **Analyzing the Statements**:
- **Statement A**: Both containers contain the same number of molecules. (False)
- **Statement B**: The pressure in the nitrogen flask is greater than in the oxygen flask. (True)
- **Statement C**: More molecules are present in the oxygen flask. (False)
- **Statement D**: Molecules in the oxygen flask are moving faster on average than those in the nitrogen flask. (False)

6. **Conclusion**:
- The correct answer is **Statement B**: The pressure in the nitrogen flask is greater than in the oxygen flask.