5) A mole of diatomic oxygen molecules and a mole of diatomic nitrogen molecules are at STP. Which statements are true about these molecules? (There could be more than one correct choice.) A) Both gases have the same average momentum per molecule. B) Both gases have the same average molecular speeds. C) Both gases have the same average kinetic energy per molecule. D) Both gases have the same number of molecules.
Kinetic Theory of Gas
The Kinetic Theory of gases is a classical model of gases, according to which gases are composed of molecules/particles that are in random motion. While undergoing this random motion, kinetic energy in molecules can assume random velocity across all directions. It also says that the constituent particles/molecules undergo elastic collision, which means that the total kinetic energy remains constant before and after the collision. The average kinetic energy of the particles also determines the pressure of the gas.
P-V Diagram
A P-V diagram is a very important tool of the branch of physics known as thermodynamics, which is used to analyze the working and hence the efficiency of thermodynamic engines. As the name suggests, it is used to measure the changes in pressure (P) and volume (V) corresponding to the thermodynamic system under study. The P-V diagram is used as an indicator diagram to control the given thermodynamic system.
![### Problem 5: Analysis of Diatomic Gases at Standard Temperature and Pressure (STP)
**Context**:
Consider a mole of diatomic oxygen molecules (O₂) and a mole of diatomic nitrogen molecules (N₂) both at standard temperature and pressure (STP).
**Question**:
Which statements below are true about these molecules? (Note: There could be more than one correct choice.)
**Statements**:
A) Both gases have the same average momentum per molecule.
B) Both gases have the same average molecular speeds.
C) Both gases have the same average kinetic energy per molecule.
D) Both gases have the same number of molecules.
**Considerations for Answering**:
- At STP, both gases are under the same temperature and pressure conditions.
- One mole of any ideal gas contains Avogadro's number of molecules, which is approximately \(6.022 \times 10^{23}\) molecules.
**Detailed Analysis**:
- **Average Momentum**: The momentum of a molecule is a product of its mass and velocity. Since oxygen and nitrogen molecules have different masses, their average momentum per molecule would differ even if their velocities were the same.
- **Average Molecular Speeds**: According to the kinetic theory of gases, the average speed of a gas molecule depends on the mass of the molecule. Since O₂ and N₂ have different molecular masses, their average speeds will be different.
- **Average Kinetic Energy**: Kinetic energy for gas molecules at a given temperature is given by \(\frac{3}{2} k_B T\), where \(k_B\) is Boltzmann's constant and T is the temperature. This is independent of the mass of the molecule, meaning O₂ and N₂ molecules at the same temperature have the same average kinetic energy.
- **Number of Molecules**: By definition, one mole of any substance contains the same number of molecules, Avogadro’s number. Therefore, a mole of O₂ and a mole of N₂ will contain the same number of molecules.
**Conclusion**:
From the given statements:
- **Statement C (True)**: Both gases have the same average kinetic energy per molecule.
- **Statement D (True)**: Both gases have the same number of molecules.
Thus, the correct answers are **C** and **D**.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1b9cb62c-f591-4b8c-98ff-d2fca4be80ae%2Febb0219d-3072-4a02-b612-59bde30efe63%2Ftusj0mb_processed.png&w=3840&q=75)
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