# Speed of a Molecule Question

1. Oct 15, 2009

### solsek

1. The problem statement, all variables and given/known data

Consider a gas-phase N2 molecule. It's RMS speed is given by

Vrms = (3kT/m)^(1/2)

What speed would the gas molecule have if it had the same energy as a photon of the following wavelengths of IR, visible, UV and X-Ray electromagnetic radiation?

lambda = 1.000E4nm, 500nm, 100nm, 0.10nm

2. Relevant equations

E=hc, E=hc/lambda E = (mv^2)/2 , not sure if we should use lambda = h / p (momentum)

3. The attempt at a solution

So I don't know how to use the Vrms equation that is given in the problem. I am not sure if we need to use it at all (Btw, this in the first problem set of my pchem class so it should be pretty easy, I am just not sure if I am doing it right).

E = hc/lambda, using this equation we can find the energy of the gas molecule if it had the wavelength given in the problem.

Once we find the energy E we can use KE = 1/2mv^2 to some for v.

I am not sure if we are supposed to use this method or use the Debroglie equation where lambda = h / mv and solve for velocity that way.

Any thoughts?

2. Oct 15, 2009

### rl.bhat

What is the temperature of N2?
Use Debroglie formula to find wavelength.

3. Oct 15, 2009

### solsek

We aren't given a temperature of N2. We don't know velocity, so I don't see how we can use debroglie forumla to solve for wavelength. Wavelength is given in the problem, should it be converted to a different wavelength?

4. Oct 15, 2009

### rl.bhat

Use wavelengths in the problem.