# How do you solve ideal gas law problems?

Mar 2, 2014

The units of Ideal gas law constant is derived from equation PV = nRT?

Where the pressure - P, is in atmospheres (atm) the volume - V, is in liters (L) the moles -n, are in moles (m) and Temperature -T is in Kelvin (K) as in all gas law calculations.

When we do the algebraic reconfiguration we end up with Pressure and Volume being decided by moles and Temperature, giving us a combined unit of
atm x L / mol x K. the constant value then becomes 0.0821 atm(L)/mol(K)

If you choose not to have your students work in standard pressure unit factor, you may also use: 8.31 kPA(L)/mol(K) or 62.4 Torr(L)/mol(K).

Temperature must always be in Kelvin (K) to avoid using 0 C and getting no solution when students divide.

There is a variation of the ideal gas law that uses the density of the gas with the equation PM = dRT

Where M is the Molar Mass in g/mol and d is the Density of the gas in g/L.

Pressure and Temperature must remain in the units atm and K and the Gas Law Constant remains R = 0.0821 (atm) L / (mol) K.