The choice of chemical ingredients in airbags significantly influences their effectiveness. According to the passage, there are several factors to consider:
1. Volume of gas produced: The chemical that produces the greatest volume of gas will inflate the airbag the most effectively. For example, the decomposition of nitroglycerin produces nearly 5 times the moles of gas as sodium azide or ammonium nitrate for the same mass of starting material.
Data:
Nitroglycerin: Nearly 5 times moles of gas, 4 moles of liquid starting material
Sodium azide: Generates solid sodium and nitrogen gas
Ammonium nitrate: Generates dinitrogen monoxide (N2O) and water vapor (H2O); requires half the amount of solid starting material to produce the same 3 total moles of gas.
2. Rate of gas production: The chemical that produces gas the fastest will inflate the airbag quickest, ideally deflating before the occupant impacts the bag. According to the passage, sodium azide decomposition ignites the charge and inflates the airbag at about 200 mph, taking 1/25 of a second.
Data:
Sodium azide decomposition: Inflates airbag at 200 mph in 1/25 sec
3. Non-toxic and stable products: The chemical decomposition should produce harmless, non-explosive products that do not pose risks to vehicle occupants. Sodium azide and ammonium nitrate are preferred over nitroglycerin which is too shock-sensitive. Potassium nitrate and silicon dioxide are added to sodium azide to convert the sodium metal product to harmless compounds.
Data:
Sodium azide decomposition: Produces sodium metal which is reactive and explosive; requires additional compounds to convert to harmless products.
Ammonium nitrate decomposition: Produces dinitrogen monoxide (N2O) and water vapor (H2O) which are non-toxic.
Nitroglycerin decomposition: Produces explosive products; too shock-sensitive and difficult to control.
In summary, the effectiveness of airbag chemicals depends on producing the greatest volume of gas the fastest while yielding only non-toxic, stable products. Sodium azide and ammonium nitrate are preferred over nitroglycerin due to these factors. Potassium nitrate and silicon dioxide are added to sodium azide to manage the reactivity of its products. The data clearly shows how each chemical's properties influence its effectiveness for inflating airbags.
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