Relationship between Molar Mass and Velocity of Hydrogen and Oxygen

[ssb]

Homework Statement

Lets say at room temp an atom of hydrogen moves at 3000 m/s. Let's 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?

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.

 

[Dick]

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

 

[ssb]

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

well then if that's the case then the velocity would stay the same... right?

 

[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?

 

[ssb]

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

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.

 

[Dick]

That's much better.

 

[ssb]

That's much better.

heheheh thankyou very much