Question

Automobile airbags contain solid sodium azide, NaN3, that reacts to produce nitrogen gas when heated, thus inflating the bag. 2NaN3(s)⟶2Na(s)+3N2(g) Calculate the value of work, w, for the system if 24.0 g NaN3 reacts completely at 1.00 atm and 22 °C.

W=?J

Answer 1

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

= 1*22.99 + 3*14.01

= 65.02 g/mol

mass of NaN3 = 24.0 g

mol of NaN3 = (mass)/(molar mass)

= 24.0/65.02

= 0.3691 mol

From balanced chemical reaction, we see that

when 2 mol of NaN3 reacts, 3 mol of N2 is formed

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

= (3/2)*0.3691

= 0.5537 mol

we have:

P = 1.0 atm

n = 0.5537 mol

T = 22.0 oC

= (22.0+273) K

= 295 K

we have below equation to be used:

P * V = n*R*T

1 atm * V = 0.5537 mol* 0.0821 atm.L/mol.K * 295 K

V = 13.41 L

W = -Pext(Vf-Vi)

P = 1.0atm

Vi = 0.0 L

Vf = 13.41 L

put values in above expression

W = -Pext(Vf-Vi)

W = -1.0atm (13.41L - 0.0L)

W = -13.41 atm.L

W = -13.41 *101.33 J

W = -1359 J

Answer: -1359 J