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 following system if 32.8 g of NaN3 reacts completely at 1.00 atm and 22 °C.

Answer 1

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

no of moles of NaN3 = W/G.M.Wt

                                   = 32.8/65    = 0.505moles

2 moles of NaN3 decomposes to gives 3 moles of N2

0.505 moles of NaN3 decomposed to gives = 3*0.505/2   = 0.7575 moles of N2

PV = nRT

T = 22+273 = 295K

P = 1atm

V   = nRT/P

      =0.7575*0.0821*295/1   = 18.35L

W = -PV

      = -1*18.35 = -18.35L-atm

[ 1L-atm = 101.3J]

      = -18.35*101.3   = -1858.855J