How do you calculate the ideal gas law constant?

The is PV = nRT, where R is the Universal Gas Constant or Ideal Gas Constant.

We can rearrange this to get R = PV/nT

To calculate R, you must do an experiment in which you measure the values of P, V, n, and T. You then insert these values into the equation. The units of R depend on the units you use for P and V.

For example, repeated experiments show that at standard temperature (273.15 K) and pressure (1 atm), 1 mol of gas occupies 22.414 L. You can use this information to evaluate R. R = PV/nT = 1 atm ×22.414 L/(1 mol × 273.15 K) = 0.082 057 L•atm•K⁻¹mol⁻¹

If the pressure is measured in kilopascals (1 atm = 101.325 kPa), you calculate R = PV/nT = 101.325 kPa × 22.414 L/(1 mol × 273.15 K) = 8.3145 kPa•L•K⁻¹mol⁻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 × 10⁵ Pa × 22.414× 10⁻³ m³//(1 mol × 273.15 K) = 8.3145 Pa•m³K⁻¹mol⁻¹

The most common values of R are R = 0.082 057 L•atm•K⁻¹mol⁻¹ R = 8.3145 kPa•L•K⁻¹mol⁻¹ R = 8.3145 Pa•m³K⁻¹mol⁻¹ R = 8.3145 J•K⁻¹mol⁻¹

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