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.
- Avogadro’s law states that the volume of a gas is proportional to the amount of the gas (at constant temperature and pressure.
- 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).
The combination of these three laws is:
This law can be rearranged to:
The proportional relationship can be written as equation: , where R is a proportional constant termed the gas constant. The value of R (in SI unit) is:
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 in an automobile air-bag safety system. This reaction utilizes the rapid decomposition of sodium azide.
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.
Which statement regarding the above chemical reaction is true: