How to claculate value of universal gas constant?

1 Answer
Jan 8, 2017

Answer:

You must do an experiment in which you measure the values of #P, V, n#, and #T#.

Explanation:

The Ideal Gas Law is

#color(blue)(bar(ul(|color(white)(a/a) PV = nRTcolor(white)(a/a)|)))" "#

where

#P# = the pressure
#V# = the volume
#n# = the number of moles
#R# = the Universal Gas Constant
#T# = the temperature

We can rearrange the Ideal Gas Law to get

#R = (PV)/(nT)#

If you do an experiment in which you measure the values of #P, V, n#, and #T#, you can insert these values into the equation and calculate #R#.

For example, repeated experiments show that at standard temperature and pressure (273.15 K and 1 bar), 1 mol of gas occupies 22.711 L.

You can use this information to evaluate #R#.

#R = (PV)/(nT) = ("1 bar" × "22.711 L")/("1 mol × 273.15 K") = "0.083 145 L·atm·K"^"-1""mol"^"-1"#

If you use strictly SI units, then pressure is measured in pascals and volume is measured in cubic metres.

#R = (PV)/(nT) = (1.013 25 × 10^5 color(white)(l)"Pa" × 22.414× 10^"-3"color(white)(l) "m"^3)/"1 mol × 273.15 K" = "8.3145 Pa·m"^3"K"^"-1""mol"^"-1"#

Always make sure that you use the value of #R# corresponding to the units that you are using for #P# and #V#.