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Scan_Doc0110 - forms hydrazoic acid(HN3 a toxic and...

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202 Chapter Five Gases TheChemistry of Air Bags Most experts agree that air bags represent a very important advance in automobile safety. These bags, which are stored in the auto's steering wheel or dash, are designed to inflate rapidly (within about 40 ms) in the event of a crash, cushioning the front-seat occupants against impact. The bags then deflate immediately to allow vision and movement after the crash. Air bags are activated when a severe deceleration (an impact) causes a steel ball to compress aspring and electrically ignite adetonator cap, which, in turn, causes sodium azide (NaN3) to decompose explosively, forming sodium and nitrogen gas: 2NaN3(S) ---+ 2Na(s) + 3N 2 (g) This system works very well and requires a relatively small amount of sodium azide (100 g yields 56 L N 2 (g) at 25°C and 1.0 atm). When a vehicle containing air bags reaches the end of its useful life, the sodium azide present inthe activators must be given proper disposal. Sodium azide, besides being explosive, has a toxicity roughly equal to that of sodium
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Unformatted text preview: 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. Inflated air bags. Therefore, we can represent the mole fraction in terms of pressures: III ~ nl PI(V/RT) Xl = ~~ = --------~OTAL PI(V/RT) + PiV/RT) + P 3 (V/RT) + ... '-----v-------' '-----v-------' '-----v-------' III 112 IlJ (V/RT)P I (V/RT)(P I + P 2 + P 3 + :. .) PI PI PI + P 2 + P 3 + ... P TOTAL In fact, the mole fraction of each component in a mixture of ideal gases is directly related to its partial pressure: n2 P 2 X2=~~=---nTOTAL P TOTAL EXAMPLE 5.16 The partial pressure of oxygen was observed to be 156 torr in air with a total atmospheric pressure of 743 torr. Calculate the mole fraction of O 2 present. Solution Where are we going? • To determine the mole fraction of O 2...
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