Properties of Gases

Increasing the temperature allows a gas to absorb thermal energy and convert into kinetic energy. Kinetic energy allows the gas to move and the speed at which it moves gives us the root mean square speed

Root Mean Square Speed & Kinetic Energy

Concept: Understanding kinetic energy & Root Mean Square Speed


Example: A 1.56 x 1013 pg gaseous particle travels at 6.21 . Determine its kinetic energy. 


The kinetic energy (in J or kJ) of a gas molecule is directly proportional to its absolute temperature in Kelvins. 

Problem: Calculate the molar mass, in g/mol, of a gaseous compound with an average root mean velocity of 652 m/s at a temperature of 30 degrees Celsius.


Remember that using the root mean square speed equation deals with molar mass in g/mol, so further conversion may sometimes be needed. 

Graham's Law of Effusion

Effusion is the rate at which a gas escapes a container with an opening in it. 

Concept: Understanding Graham's Law of Effusion


When comparing the rate or speed of two gases then we must use Graham’s Law of Effusion

Example: Calculate the ratio of the effusion rates of helium and methane (CH4). 


The gas named first will represent gas 1 and the second gas will represent gas 2. Once that is established we simply use Graham’s Law of Effusion. 

Example: Rank the following in order of increasing rate of effusion: 

O2                    AlF5                  CO2                 Xe