Question

14. "Air" bags for automobiles are inflated during a collision by the explosion of sodium azide, NaN3. The equation for the decomposition is 2NaN3(s) → 2Na(s) + 3N2(g). What mass of sodium azide would be needed to inflate a 9.1-L bag to a pressure of 1.1 atm at 25°C?

Answer 1

Given:

P = 1.1 atm

V = 9.1 L

T = 25.0 oC

= (25.0+273) K

= 298 K

find number of moles using:

P * V = n*R*T

1.1 atm * 9.1 L = n * 0.08206 atm.L/mol.K * 298 K

n = 0.4091 mol

This is number of moles of N2 in reaction

2NaN3(s) → 2Na(s) + 3N2(g)

From balanced reaction above,

moles of N2 = (2/3)*moles of N2

= (2/3)*0.4091 mol

= 0.2727 mol

Molar mass of NaN3,

MM = 1*MM(Na) + 3*MM(N)

= 1*22.99 + 3*14.01

= 65.02 g/mol

mass of NaN3,

m = number of mol * molar mass

= 0.2727 mol * 65.02 g/mol

= 17.7 g

Answer: 17.7 g