# Speed of Hydrogen / oxygen

1. Nov 30, 2007

### ssb

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

Lets say at room temp an atom of hydrogen moves at 3000 m/s. Lets say all things the same except you replace the hydrogen with oxygen. The oxygen is about 16 times the molar mass than hydrogen. Does this mean that the oxygen will travel at (1/16)*3000 m/s?

3. The attempt at a solution

This is not really a homework question but we are dealing with stuff like this in class and it has been confusing me. 1/16 times the original velocity is my guess.

2. Nov 30, 2007

### Dick

That's a wrong guess. It's the kinetic energy of the molecules that remains the same.

3. Nov 30, 2007

### ssb

well then if thats the case then the velocity would stay the same... right?

4. Nov 30, 2007

### Dick

Nooooo! KE=(1/2)*m*v^2. So mH*vH^2=mO*vO^2. If mO=16*mH, how are vH and vO related?

5. Nov 30, 2007

### ssb

this would make

sqrt(1/16*vH^2) = sqrt(vO^2)

so vO would = 1/4 vH

so if H was moving at 3000 m/s then O would be moving at 750 m/s.

6. Nov 30, 2007

### Dick

That's much better.

7. Nov 30, 2007

### ssb

heheheh thankyou very much