Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: mycotheologist on April 23, 2012, 06:36:16 PM
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On the wiki page theres a table of values for different units. I don't understand what they mean though. For example, the value for litre torr per mol kelvin is 62.36367(11). What does the (11) mean? In this tutorial:
http://www.mikeblaber.org/oldwine/chm1045/notes/Gases/Density/Gases05.htm
they use 6236 as the value for that gas constant in those units. I'm lost.
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you typed (omitting the decimal point)
6236
The mikeblaber.org page is different from what you have typed -- it is
62.36 L torr/mol K
Do you see the similarity to
litre torr per mol kelvin is 62.36367(11)
The various units are measured in absolute values. So, for instance. you would use K (kelvin) for temperature and not C (centigrade).
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There are the only two R values you need:
R = 8.314472 J mol^-1 K^-1
Note the units contain J, hence use for energy calculations -nFE° = ΔG = ΔH – TΔS = -RTln K;
rate = Aexp-(Ea/RT) because your energies are in J mol^-1 convert kJ→J, g→mol; and T in K.
R = 0.0820574 L atm mol^-1
For the Ideal Gas Eqn PV = nRT
Note units of L atm mol^-1
So get your Pressure into atm (eg ÷ torr by 760) and V in L (÷ mL by 1000) K; g→mol;
once again T in K = T°C + 273.2 n in mol
The (11) is the standard deviation in the last two numbers; it gives an indication of the experimental
uncertainty in R.
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It's a degree of accuracy