Air bag and sodium azide

[sarahswaheli]

Hi,
I am having problems with this one....

Air bags are activated when a severe impact causes a steel ball to compress a spring and electrically ignite a detonator cap. This causes sodium azide (NaN3) to decompose explosively according to the following reaction...
2NaN3 -----> 2Na + 3N2

What mass of NaN3 must be reacted to inflate an air bag to 70.0 L @ STP?

Any ideas??
Thanks.

[RobJim]

First, you use the ideal gas law to figure out how many moles of gas would inflate the airbag to that volume under those conditions. Then, figure out how many moles of NaN3 would need to decompose in order to produce that many moles of gas.