Your lab work this semester has spanned topics as diverse as calorimetry and stoichiometry. This lab will require you to synthesize many of the practical and computational skills that you have acquired during your lab tenure. You will generate your own procedure and data collection and will work in competition with the other lab groups in your section. You will submit this lab as a handwritten lab report today and will write your second formal report on your lab findings for submission as a signature project at a future date. In addition to your handwritten report, your airbag, calculations, and engineering will be judged in class. Some of the questions that will be asked in an interview are:
The chemistry process and calculations that you use in creation of an airbag supersede the performance of the airbag itself.
How does an Airbag Work?
An automobile airbag must both inflate quickly and produce inert, non-flammable products to be both safe and useful. Modern air bags accomplish both through a sodium azide (NaN3(s)) reaction, which inflates an airbag in less than 0.3 seconds. An open bag design ‘softens’ the large airbag, which is designed to both reduce acceleration and distribute force over a greater area than a steering wheel or car interior, reducing injuries. The chemistry involved is both elegant and precise. Stoichiometric masses of reactants must be used to ensure a complete reaction toward the inert nitrogen gas and silicon dioxide (glass) products according to the following reactions. The first of which is the electrical ignition of the sodium azide explosive when a sensor communicates a collision.
2NaN3(s) à 2Na(s) + 3N2(g) Reaction 1
The highly reactive sodium metal produced in reaction one is further reacted with solid potassium nitrate in a second reaction to produce a less reactive oxide and still more nitrogen gas.
10 Na(s) + 2 KNO3(s) à K2O(s) + 5 Na2O(s) + N2(g) Reaction 2
Reactions one and two can be summed to the following reaction.
10 NaN3(s) + 2 KNO3(s) à 5 Na2O(s) + K2O(s) + 16 N2(g) Reaction 3
The solid products are then combined with solid silicon dioxide in a fourth reaction to produce a safe and inflammable product, glass.
K2O(s) + Na2O(s) + SiO2(s) à glass Reaction 4
Some elements of the sodium azide detonation can be reproduced in lab. Using an explosive in a lab setting that allows for trials is unsafe. You can, however, safely produce an inert gas in a more controlled (slow) manner. Like the sodium azide detonation, you should consider that all the products of your reaction will be present after a collision.
Objective:
Safety:
Waste/Housekeeping:
Materials:
Procedure/Data Collection/Analysis: