Posted by Christina on Sunday, December 9, 2007 at 8:44pm.
Oxygen (O2) has a molar mass of 32.0 g/mol [.032kg/mol].
What is the root-mean-square speed of an oxygen molecule at a temperature of 310 K?
What is its average translational kinetic energy at that speed?
Kav= ?? J
I am having problems with the second half, finding the Kav...
Physics - drwls, Sunday, December 9, 2007 at 9:03pm
You can get Kav by calculating
(1/2) M [Vrms]^2.
You can also get it from the general rule
Etr,average = (3/2) kT
where k is Boltzmann's constant, 1.38*10^-23 Joule/K. It applies to all molecules.
Physics - Christina, Sunday, December 9, 2007 at 9:11pm
Here is what I've done, hopefully you can identify where I've gone wrong..
Physics - bobpursley, Sunday, December 9, 2007 at 9:14pm
Since when is the mass of an O2 molecule .032 kg?
You missed it by a very large factor. .032kg is aobut one ounce, which would be a very large molecule...
Physics - Christina, Sunday, December 9, 2007 at 9:19pm
ok, that makes much more sense...
then i'm assuming that:n=2 for O2 and the m is .032 ????
Physics - DrBob222, Sunday, December 9, 2007 at 9:36pm
The question is for ONE oxygen molecule. 0.032 kg is the mass of a MOLE of oxygen molecules.
Physics - Christina, Sunday, December 9, 2007 at 9:39pm
I am beyond lost..I've never had any chemistry and our professor assumed that we had at least a basic knowledge...is there any way you could walk me thought this?
Physics - DrBob222, Sunday, December 9, 2007 at 9:56pm
No, for I've forgotton what little physics I knew at one time; however, you know (from your chemistry if not physics) that 1 mol of oxygen (0.032 kg) contains 6.02 x 10^23 molecules. So how much does 1 molecule weigh? The problem is asking for 1 molecule, not 6.02 x 10^23 molecules.
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