air bags actived when a severe impact causes a steel ball to compress a spring and electrically ignite a detonator cap. this causes NaN3 to decompose explosively according to the following reaction:

2NaN3(s)=2Na(s)+3N2(g)

what mas of NaN3 must be reacted to inflate an air bag to 70.0L at 0C & 1.00 atm?

is this correct:

n(N2): PV/RT
n=1.00 atm x 70.0L/0.0821(L*atm/mol*K) x273K = 3.12 mol N2

mass NaN3 reacted:

(3.12 mol N2) x (2mol NaN3/3molN2)x (65.02gNaN3/1molNaN3)= 135g NaN3

please let me know if I'm doing this correct and where can I find more examples to practice more, have my test tomorrow...thankx. :)