posted by Anonymous .
I got some questions about air bags. Can someone please help me out? Thamks in advance for giving me any information about that.
1. Which starting material used in the air bag inflator is least important for the proper inflation of the air bag? Would it be necessary to have it present in a precise stoichiometric ratio? Why or why not?
2. What is the correct stoichiometric ratio between NaN3 and KNO3 to ensure no sodium is unreacted? What would be the consequences of an excess of KNO3 to the operation of an air bag?
I knew the balanced equations that undergo these reactions...
I hope this can help...
I think talcum powder or cornstarch is used as a lubricant. Perhaps that is what is referred to in #1. The amount of powder need not be precise.
For #2, if you will multiply equation 1 by 5 and add it to equation 2 as is, you will come out with
10NaN3 + 2 KNO3 ==>16N2 + K2O + 5Na2O.
Check that to make sure it is correct. The correct ratio of NaN3 to KNO3 is 10 to 2 or 5:1. I will let you mull over the KNO3 in excess part.
According to my book, I think it only mentions about NaN3, KNO3 and SiO2 as starting materials.
Among the three, which one is least important? Would it be necessary to have it present in a precise stoichiometric ratio? Why or why not?
Thanks for your help.
The SiO2 is not necessary in a precise amount. You can see from the equations you wrote that the SiO2 is not involved in the production of the N2 gas. The SiO2 is involved in cleaning up the products of the reaction other than N2 gas. So a little more SiO2 would give some excess SiO2 which would not be harmful. A little less SiO2 and you might be left with some K2O and Na2O. K2O and Na2O could be harmful if either came in contact with moisture(for example the eyes) but of the three, the SiO2 is the least necessary for a precise stoichiometric ratio. It would be better to have a little more than to have a little less.
Will an excess of KNO3 produce more K2O, 5Na2O and N2 or not?
No. If NaN3 is the limiting reagent (which is the case if KNO3 is in excess), then no more N2 will be produced by using an excess of KNO3.
A possible reaction for KNO3, under increased temperature is
2KNO3 + heat ==> 2KNO2 + O2
So if KNO3 is in excess and it's just popped out of the inflated bag and nothing else happens, then I don't think the KNO3 would have a damaging effect. However, as we all know, in accidents, many things can happen. IF the temperature goes up(for example, a fire starts (not all that unusual), then the KNO3 could produce oxygen and we certainly don't want any excess oxygen around with a fire.
what is the correct stoichiometric ratio between NaN3 and KNO3 to insure no sodium is reacted.
what is the consequences of excess of KNO3 to the operation of an air bag?
Thanks for the help! I'mm doing a C^3 assignment and DrBob222 really helped! Thanks again!