# Homework Help: Average kinetic energy

1. Sep 7, 2008

### Punjabi.Sher

A gas contains a mixture of He and Ne.
The gas is at a temperature of 448 K, with
0.85 mole of He and 2 mole of Ne.
Avogadro’s number is 6.02 × 1023 mol−1,
and Boltzmann’s constant is 1.38×10−23 J/K.
What is the average kinetic energy per
molecule of He? Answer in units of J.

2. KE(bar) = (1/2)mv² = (3/2)kT

3. The middle equation above gives you the average kinetic energy, but I dont have any velocity. Can someone please guide me with this problem?

2. Sep 7, 2008

### Ygggdrasil

What's wrong with using KE(bar) = (3/2)kT?

3. Sep 7, 2008

### Punjabi.Sher

wow, it was just a matter of typing it in correctly. I can't believe this, because I am doing these online, so I didn't know how to type in very small values like with exponents.

4. Sep 7, 2008

### Punjabi.Sher

Ok theres part 2 to this question. It looks so similar to this, but the same method doesnt give me the right answer.

Part 2: What is the average kinetic energy per
molecule of Ne?

Part 3: What is the average total kinetic energy of
He? Answer in units of J.

5. Sep 7, 2008

### Ygggdrasil

For part 3 it sounds like the want average kinetic energy per atom of He * number of atoms of He.