Where did the ideal gas law come from?

The ideal gas law formula is originally attributed to Emile Clapeyron, who was supposedly the first to write it down, essentially combines the three laws of Robert Boyle, J.A.C. Charles, and Amedeo Avogadro:

Boyles Law - states volume is inversely proportional to pressure

Charles' Law - States that volume is proportional to temperature

Avogadro's Law - States that volume is proportional to number of moles

For even more applications, the ideal gas law can also be rearranged to solve for density and molar mass by substituting the number of moles for the equivalent mass/molar mass and substituting mass/volume with density.

n = mass/molar mass

d = mass/volume

The Ideal gas law can conveniently be rearranged to solve for any variable. Also, you can set up a proportion to determine the change in one variable before and after a reaction if you know how how the other variables change.The subscripts 1 and 2 refer to initial and final conditions.

Always getting the wrong answer?

The #1 mistake students make when plugging values into the ideal gas law formula is not converting the units of their known values into units that are used for the value of R, this way they'll all cancel out except for the units of the answer. Volume should always be in liters (L), pressure in atmospheres (atm), and Temperature in Kelvin (K): These are the standard ideal gas law units.

Remember to add 273 to your given Temperature in Celcius to get the Temperature in Kelvin. (Eg. 25C is 298K) before plugging it into PivNert.



P = Pressure

V = Volume

n = number of moles

R = 0.0821L*atm/(mol*K) 

T = Temperature

Definition of the ideal gas law:

We define ideal gas law as the relationship among pressure, volume, temperature, and number of moles of an ideal gas, that is, a hypothetical gas that exhibits a linear relationship at every condition and every molecular collision is perfectly elastic. We can use this equation in the sciences to approximate very simple gases.

  • When using 0.0821Latm/molK for R, try to convert all your given values into liters, atm, and Kelvin. These should all cancel and leave your answer with the correct unit.

  • If you think you are missing a value for the Ideal Gas Law Equation, remember that 1 mole of any at standard temperature and pressure has a volume of 22.4L. STP is given below: