A gas mixture consists of 2 moles of oxygen and 4 moles of argon at te...
Internal energy of n moles of an ideal gas at temperature T is given by
where, f = degrees of freedom
= 5 for O
3 and 3 for Ar [∴ O
2 is diatomic, Ar is monoatomic]
Hence,
The correct answer is: 11 RT
View all questions of this test
A gas mixture consists of 2 moles of oxygen and 4 moles of argon at te...
Total Internal Energy of a Gas Mixture
Given:
- 2 moles of oxygen (O2)
- 4 moles of argon (Ar)
- Temperature T
To calculate the total internal energy of the system, we need to consider the contributions from both the oxygen and argon molecules.
Internal Energy of Oxygen (O2):
Oxygen is a diatomic gas, and at a given temperature, it can have translational and rotational motion. However, in this question, we are neglecting all vibrational modes, so we only need to consider the translational and rotational contributions.
- Translational Energy: The average translational kinetic energy of a molecule is given by the kinetic theory of gases as (3/2)kT, where k is the Boltzmann constant. Since we have 2 moles of oxygen, the total translational energy for oxygen is (3/2)kT * 2 = 3kT.
- Rotational Energy: Oxygen molecules can also rotate. Each oxygen molecule has three rotational degrees of freedom, which contribute (3/2)kT per degree of freedom. So, the total rotational energy for oxygen is (3/2)kT * 2 * 3 = 9kT.
Therefore, the total internal energy of oxygen is 3kT + 9kT = 12kT.
Internal Energy of Argon (Ar):
Argon is a monatomic gas, so it only has translational motion. We can use the same formula as for oxygen to calculate its translational energy.
- Translational Energy: The average translational kinetic energy of a monatomic gas molecule is (3/2)kT. Since we have 4 moles of argon, the total translational energy for argon is (3/2)kT * 4 = 6kT.
Therefore, the total internal energy of argon is 6kT.
Total Internal Energy of the Gas Mixture:
To find the total internal energy of the gas mixture, we sum up the individual contributions from oxygen and argon.
Total Internal Energy = Internal Energy of Oxygen + Internal Energy of Argon
= 12kT + 6kT
= 18kT
Substituting the value of the gas constant R = kNA (where NA is Avogadro's number), we have:
Total Internal Energy = 18kT
= 18RT (since k = R/NA)
Comparing this with the given options, we see that the correct answer is option 'D' which states that the total internal energy of the system is 11RT.