The Chemistry of Air Bags

This system works very well and requires only a relatively small amount of sodium azide (100 g yields 56 L of N2(g) at 25°C and 1 atm). 

When a vehicle containing air bags reaches the end of its useful life, the sodium azide present in the activators must be given proper disposal. Sodium azide, besides being explosive, has a toxicity roughly equal to that of sodium cyanide. It also forms hydrazoic acid (HN3), a toxic and explosive liquid, when treated with acid. 

The air bag represents an application of chemistry that has already saved thousands of lives.  

This important result indicates some fundamental characteristics of an ideal gas. The fact that the pressure exerted by an ideal gas is not affected by the identity (structure) of the gas particles reveals two things about ideal gases (1) the volume of the individual gas particle must not be important and (2) the forces among the particles must not be important. If these factors were important, the pressure exerted by the gas would depend on the nature of the individual particles. These observations will strongly influence the model that we will eventually construct to explain ideal gas behavior. 

At this point we need to define the mole fraction the ratio of the number of moles of a given component in a mixture to the total number of moles in the mixture. The Greek letter chi (x) is used to symbolize the mole fraction. For a given component in a mixture, the mole fraction (Xi) is 

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One of the problems with air bags (see Figure 12.15 on the next page) is that they can harm a child or small adult because too much gas is produced. To find out what volume of nitrogen gas in an air bag is safe for a child, go to the web site above. Go to Science Resources, then to Chemistry 11 to find out where to go next. Use the volume you find to calculate the mass of NaN3(s> that is needed to produce this volume at 22.0°C and 105 kPa. 

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