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Topic: Help - Gas Laws - Dalton's Law (?)  (Read 3093 times)

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Offline BlockHead

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Help - Gas Laws - Dalton's Law (?)
« on: May 28, 2007, 01:24:20 PM »
I have a question on my homework that's gotten me stumped. The question reads:

If 64.2 grams of Oxygen gas occupies a volume of 100 L at a particular temperature and pressure, what volume will 5.00 grams of Oxygen gas occupy under the same conditions?

So far, the only thing I came up with was converting my grams of oxygen to moles.

64.2g O2 = 2.01 mol
5.00g O2 = .16 mol

I think this may be a problem pertaining to Dalton's Law but I'm a bit stuck here. Any help is appreciated!

Offline Yggdrasil

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Re: Help - Gas Laws - Dalton's Law (?)
« Reply #1 on: May 28, 2007, 01:40:20 PM »
So, you know the ideal gas law is PV = nRT.  In this problem, P and T are fixed.  So, it is useful to move all of the constant terms to one side of the equation and move all of the non-constant terms to the other side of the equation.  After some rearranging, you get:

V/n = RT/P = C

Since RT/P is constant (C), that means that:

Vinitial/ninitial = C

and


Vfinal/nfinal = C

or

Vinitial/ninitial = Vfinal/nfinal

Using this approach, you can also derive some to the other simplified ideal gas laws, like Charles' law (V1/T1 = V2/T2) or Boyle's law (P1V1 = P2V2).

Offline Borek

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Re: Help - Gas Laws - Dalton's Law (?)
« Reply #2 on: May 28, 2007, 01:42:02 PM »
pV=nRT

V = (RT/p) n

For given pressure and temperature RT/p = const, thus

V = k n

Edit: Ygg beat me :(
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