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Ideal Gas Law Formula

The gas in which every molecule behaves autonomous of every individual molecule and has no excluded volume is called an ideal gas. Ideal Gas Law Formula is arithmetically articulated as:


from which simpler gas laws such as Amonton’s, Avogadro’s, Charles’s and Boyle’s law were derived.

One must highlight that this gas law is based on ideal situation. As chemists, instructors, and scholars, we from time to time need to comprehend the concepts in advance before we can use them, and to suppose, unaffected by real world conditions, the gases are in an ideal state; it will help us better comprehend the behavior the gases. Gas’ behavior must follow the Kinetic-Molecular Theory to be ideal, whereas the Non-Ideal Gases will deviate from this theory due to real world situations.


Ideal Gas Law Problems

Solved Examples

Problem 1: What is the temperature of One mole of CH4 gas that occupies 20.0L at 1.00atm pressure in Kelvin?


Answer the ideal gas law for T and put in the given values.

T = fracPVnR

T = fracPVn times frac1R

T = frac[1.00atm][20.0L]1.00mol times fracmol.K0.0821L.atm

T = 244K

Remember that under these conditions we computed the temperature for 1.00 mol of CH4 gas. The solution would be similar for 1.00 mol of NH3, N2, CO2 or any other gas underneath these settings.


Problem 2: What is the gas pressure within a cylinder if there is 5.0g of CO2 gas in a 10 L cylinder at 25oC inside it.


The measure of CO2 has been presented in grams but to apply the ideal gas law, we must convert the quantity into moles. For that reason, one must initially convert grams of CO2 to moles, and then use this value in the ideal gas law.

To convert into moles from grams we use 1 mol CO2 = 44g as the conversion factor.

5.0g CO2 times frac1molCO244gCO2 = 0.11 mol CO2

To solve for the pressure of the gas, we now use this value in the ideal gas equation.

Ideal Gas Law Formula

P = fracnRTV

P = frac[0.11molCO2][298K]10L times frac0.0821L.atmmol. K

P = 0.27atm