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Ideal Gas Law

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heathermm:
OK so I am doing my lab in chemistry and now i have to do my lab write up and calculations I have to use the ideal gas law
PV=nRT  
I am so confused on how to find R????
and for n am i suppose to use g/MM????
Please if anyone can help me I need it!!! thanks

Demotivator:
R is a constant that is usually given. R = .08206  if pressure is in  atmospheres, volume in liters and temp in Kelvin.

n = grams of gas/Molecular weight

AWK:
R you may always calculate from ideal gas law for 1 mole of gas at STP for any units of volume, pressure and mass. Only temperature should be in Kelvins.
R=pV/T for 1 mole of gas in STP

jdurg:
At STP, one mole of gas occupies 22.4 Liters.  So to calculate R, you can just take 22.4/273.15 and that will give you a close approximation.

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