Explain the universal gas law?

1 Answer
Mar 13, 2017


The universal gas law, or “Ideal Gas Law” shows the interaction of pressure, volume and temperature on a gaseous substance.


The “Ideal Gas Law” developed over time from the experiments and formulas derived by several separate chemists. It was first stated by Émile Clapeyron in 1834 as a combination of the empirical Boyle's law, Charles' law and Avogadro's Law. The simplest complete form is the combined law form, or Ideal Gas Law.
#((PV)/T)_1 = ((PV)/T)_2# is applicable in all situations.

However, it is “Ideal”, meaning that no inter-molecular interactions are ‘allowed’. In real life, different molecular compositions show different amounts of inter-molecular attraction or repulsion that will affect the final state of a gas. This factor is called the fugacity , and it can affect the conditions of some gases markedly (e.g. carbon dioxide).

Therefore, care (and corrections) must be used when calculating values with this equation whenever “non-ideal” gases are used beyond fairly dilute concentrations.

It was derived by combining the relationships of each of the other general laws (Boyles Law (1627-1691), Charles' Law (1746-1823), Guy-Lussacs Law (1778-1850). The related Dalton’s Law (1766-1844) describes partial pressures.

The other primary one to remember is the relationship to moles:
PV = nRT (Avogadro’s Law (1776-1856)). Here you need to be careful to use the correct “gas constant”, R, which has different values for different dimensions.