Question

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:

NaN₃ ----> Na_(s) + N_2(g)

What mass of sodium azide must be reacted to inflate an airbag to 70.0 L at STP?

Answer 1

Molar volume of gas at STP is 22.4 L

So,

number of mol of N2 required = volume / molar volume

= 70.0/22.4

= 3.125 mol

the balanced reaction is:

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

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

= (2/3)*3.125 mol

= 2.083 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

= 2.083 mol * 65.02 g/mol

= 135 g

Answer: 135 g