These notes were written for the old IB syllabus (2009). The new IB syllabus for first examinations 2016 can be accessed by clicking the link below.

IB syllabus for first examinations 2016

Universal gas constant R

This depends on the units of the measurements used in the ideal gas equation PV=nRT

R then equals PV/nT

If n equals one (for one mole of gas) then

R = PV/T

Using SI units

pressure is measured in Nm-2 and the value at atmospheric pressure is 1.01 x 105

temperature is measured in Kelvin = 273 at STP

volume in SI units 22.41 dm3 = 2.241 x 10-5 m3

R = PV/T = (1.01 x 105 x 2.241 x 10-5) /273

R = 0.00829

When P is measured in atimospheres, and V is measured in dm3

R = PV/T

R = 1 x 22.41 / 273

R = 0.0821