The ideal gas equation
Edited BY: Shadi Asakle
Edit Date: 2016-10-08 11:34:31

The simple gas laws describe the relationships involving the pressure, volume, temperature, and amount of an ideal gas. 

  • Boyle’s law states that for a fixed amount of gas at a constant temperature, the gas volume is inversely proportional to the gas pressure. Vpropto frac{1}{p}
  • Avogadro’s law states that the volume of a gas is proportional to the amount of the gas (at constant temperature and pressure. Vpropto n
  • Charles law (also called Charles-Gay Lussac’s law) states that the volume of a fixed amount of gas at constant pressure is directly proportional to its temperature (in Kelvin).Vpropto T

The combination of these three laws is: Vpropto frac{nT}{P}

This law can be rearranged to:PVpropto nT

The proportional relationship can be written as equation: PV = nRT , where R is a proportional constant termed the gas constant.  The value of R (in SI unit) is:

R = 8.3145Jmol^{-1}K^{-1}


One well known characteristic of gases in that the expand to fill their containers and assume the shape of their containers.  A practical application of these characteristics is the reaction that forms N2(g)  in an automobile air-bag safety system. This reaction utilizes the rapid decomposition of sodium azide.

2NaN_{3}(s)overset{Delta }{
ightarrow}2Na(1) + 3N_{2}(g)


Here is a simulation that simulates gas behavior:

Gas Properties

The essential components of the system are an ignition device and a pellet containing sodium azide.  When activated, the system inflates and air bag in a very short time (milliseconds range).  Note: the liquid sodium is converted to harmless solid sodium due to special additives that are also present initially.

Picture credit:


Which statement regarding the above chemical reaction is true:

Question Created By: Shadi Asakle
Creation Date: 2016-10-07 13:11:42
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