[CHM 331] problem 9.6

[Andrew J. Pounds]

On 09/01/2012 08:39 PM,  wrote:
> Sorry, I know I haven't given you enough time to answer the last 
> question, but I have another one. For 9.6, it asks about the de 
> Broglie wavelength. From what I understood in the book de Broglie 
> related wavelength to momentum so how are we supposed to solve for the 
> wavelength without any information about the molecules speed or 
> momentum? It also asks us to compare the value to the average 
> distance between oxygen molecules at 1 bar and room temp. Is that 
> something we look up or should we also be calculating that?

I'm assuming you mean 9.7 ....

Think way back to gen chem and the equation for the average kinetic 
energy of a gas.

E = 3/2 RT

For a single gas molecule that gets modified to

E = 3/2 kT

Then use this information, E=1/2/ mv^2, E=hc/lambda, etc,, to compute 
the de Broglie wavelength.

To compute the the average distance between oxygen molecules at one bar 
and room temp, assume that you have a 1 cubic meter vessel.  At 1 atm 
and room temperature, how many oxygen molecules are in this box (the 
ideal gas law could help you here).

Once you have computed the number of gas molecules in the box, take the 
cube root of that number -- that takes us from particles/cubic meter 
down to particles/meter.

If I know that there are x particles per meter, then the inverse of that 
should be the meters/particle -- or the average distance between particles.



-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Associate Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://theochem.mercer.edu/pipermail/chm331/attachments/20120902/ea10403c/attachment.html>