Question: At the same temperature, how does the internal energy of 1 mole of hel

Question

Question: At the same temperature, how does the internal energy of 1 mole of helium gas compare with the internal energy of 1 mole of argon gas? (Select all that apply.)

1.Although the helium atoms have a smaller mass m, they move faster, and have more internal energy because ½ mv2 depends linearly on the mass but quadratically on the speed.
2. They are the same, partly because both contain the same number of atoms.
3. The argon has more internal energy, partly because its atomic mass and therefore its average kinetic energy is greater.
4. They are the same, partly because both have the same average kinetic energy per atom.
5. They are the same, partly because the average speed of the argon atoms and of the helium atoms are equal.
6. The helium has more internal energy, partly because the average speed of its atoms is greater.

Explanation / Answer

For ideal gases the change in internal energy(U) is:
U= (3nR/2) T
SO THE CHANGE IN INTERNAL ENERGY'S ONLY FUNCTION IS THE TEMPERATURE OF THE GAS.(and no. of moles)

Thus:

1. Incorrect since the average kinetic energy( .5mv^2) is proportional to the temperatures,and Temp is same so no change in U due to different masses!
2. Correct, same no. of moles an different temperature means the change in Internal Energy must be equal for these ideal gases.

3.Incorrect, obvious

4. Correct as the Average Kinetic Energy is the temprature, which is the same for both which is a reason why U is the same!

5. wrong, they have same Kinetic energies but this does not mean they have the same velocities, as their masses are different.

6. Wrong.

Leaving only 2, 4 the correct answers:)

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.