Question

Automobile air bags inflate during a crash or sudden stop by the rapid generation of nitrogen gas from sodium azide, according to the reaction:

2NaN3(s) --> 2Na(s) + 3N2(g)

How many grams of sodium azide are needed to provide sufficient nitrogen gas to fill a 45.0 × 45.0 × 25.0 cm bag to a pressure of 1.15 atm at 25.0 °C?

Answer 1

1. volume = 45.0*45.0*25.0 cm^3

   = 50625 cm^3

   = 50625 mL

   = 50.625 L

   we have:

   P = 1.15 atm

   V = 50.625 L

   T = 25.0 oC

   = (25.0+273) K

   = 298 K

   find number of moles using:

   P * V = n*R*T

   1.15 atm * 50.625 L = n * 0.08206 atm.L/mol.K * 298 K

   n = 2.381 mol

   from reaction,

   moles of NaN3 reacted = (2/3)*moles of N2 formed

   = (2/3)*2.381 mol

   = 1.587 mol

   Molar mass of NaN3 = 1*MM(Na) + 3*MM(N)

   = 1*22.99 + 3*14.01

   = 65.02 g/mol

   we have below equation to be used:

   mass of NaN3,

   m = number of mol * molar mass

   = 1.587 mol * 65.02 g/mol

   = 103 g

   Answer: 103 g