[agg241]

Hi and thanks for reading.
I have this problem that really takes some night's sleep from me! I believe this IS simple, but I don't trust my calculations! 
So here it goes:
I have oxygen (O₂). n1 = 0,0137 moles. P1 = 1,381 atm. V1 = 0,2392 L. T1 = 293,65 K (And of cource R = 0,0821 L atm moles^-1 K^-1)
I am supposed to use the ideal gas law to calculate it's volume at STP (0°C and 1 atm).
So there I have that n2 = 0,0137 moles. P2 = 1 atm. V2 = X (to be found!;)) and T2 = 273 K.
As PV=nRT, and here n and R are constants, I get nR=(PV)/T. So (P1V1)/T1=(P2V2)/T2. => Isolated for the V2, the volume of the gas at STP I get V2=(P1V1T2)/(T1P2).
So that: V2 = (1,381 atm * 0,2392 L * 273 K)/(293,65 K * 1 atm) so V2 = 0,3071 L. (Which ~equals n*22,4, which gives 0,30688).
Then of course molar volume: 1 mol of gas = 22,4 L. And 1/0,0137 = 72,9927 (which you have to multiple the nr. of moles I have to get 1 mole..) and if I multiply the volume of 0,0137 moles with that 'factor', I get 22,42 L..

This all seems to be correct to me, but however I've got some bad feeling about this... Please share your thoughts, I know I might be completely wrong!

Best regards,
AGG

[Fluoroantimonicacid]

You don't really need this pressure etc. to find its volume in STP. What is the volume of one mole gas in STP?

[billnotgatez]

google can be your friend

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/idegas.html
One mole of an ideal gas at STP occupies 22.4 liters

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure
The molar volume of any ideal gas may be calculated at various standard reference conditions as shown below:

V/n = 8.3145 × 273.15 / 101.325 = 22.414 m3/kmol at 0 °C and 101.325 kPa
V/n = 8.3145 × 273.15 / 100.000 = 22.711 m3/kmol at 0 °C and 100 kPa
V/n = 8.3145 × 298.15 / 101.325 = 24.466 m3/kmol at 25 °C and 101.325 kPa
V/n = 8.3145 × 298.15 / 100.000 = 24.790 m3/kmol at 25 °C and 100 kPa
V/n = 10.7316 × 519.67 / 14.696 = 379.48 ft3/lbmol at 60 °F and 14.696 psi (or about 0.8366 ft3/gram mole)
V/n = 10.7316 × 519.67 / 14.730 = 378.61 ft3/lbmol at 60 °F and 14.73 psi

[Borek]

Then of course molar volume: 1 mol of gas = 22,4 L. And 1/0,0137 = 72,9927 (which you have to multiple the nr. of moles I have to get 1 mole..) and if I multiply the volume of 0,0137 moles with that 'factor', I get 22,42 L..

22.4 is a volume of 1 mole of gas, you don't have to multiply it by anything else but 0.0137. Note that multiplying by 1/0.0137*0.0137 is effectively mutiplying by 1, as 0.0137 cancels out.

I got 0.3071L which is almost the same. Source of the difference is most likely R value, I used 0.082057 instead of 0.0821.