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 16.3 g NaN3 reacts completely at 1.00 atm and 22 ∘ C. w=

Respuesta :

Answer : The value of work done for the system is, 922.8 J

Explanation :

First we have to calculate the moles of [tex]NaN_3[/tex]

[tex]\text{Moles of }NaN_3=\frac{\text{Mass of }NaN_3}{\text{Molar mass of }NaN_3}[/tex]

Molar mass of [tex]NaN_3[/tex] = 65.01 g/mole

[tex]\text{Moles of }NaN_3=\frac{16.3g}{65.01g/mole}=0.251mole[/tex]

Now we have to calculate the moles of nitrogen gas.

The balanced chemical reaction is,

[tex]2NaN_3(s)\rightarrow 2Na(s)+3N_2(g)[/tex]

From the balanced reaction we conclude that

As, 2 mole of [tex]NaN_3[/tex] react to give 3 mole of [tex]N_2[/tex]

So, 0.251 moles of [tex]NaN_3[/tex] react to give [tex]\frac{0.251}{2}\times 3=0.376[/tex] moles of [tex]N_2[/tex]

Now we have to calculate the volume of nitrogen gas.

Using ideal gas equation:

[tex]PV=nRT[/tex]

where,

P = Pressure of [tex]N_2[/tex] gas = 1.00 atm

V = Volume of [tex]N_2[/tex] gas = ?

n = number of moles [tex]N_2[/tex] = 0.376 mole

R = Gas constant = [tex]0.0821L.atm/mol.K[/tex]

T = Temperature of [tex]N_2[/tex] gas = [tex]22^oC=273+22=295K[/tex]

Putting values in above equation, we get:

[tex]1.00atm\times V=0.376mole\times (0.0821L.atm/mol.K)\times 295K[/tex]

[tex]V=9.11L[/tex]

As initially no nitrogen was present. So,

Volume expanded = Volume of nitrogen evolved

Thus,

Expansion work = Pressure × Volume

Expansion work = 1.00 atm × 9.11 L

Expansion work = 9.11 L.atm

Conversion used : (1 L.atm = 101.3 J)

Expansion work = 9.11 × 101.3 = 922.8 J

Therefore, the value of work done for the system is, 922.8 J