Question

If you have 39 g of sodium azide in an air bag [2nan3 (s) -> 2na (s) + 2n2 (g)], then how many molecules of nitrogen gas will it make at stp?

Answer 1

2nan3  -->2na  +3h2
calculate  the  moles   of   nan3  =39/65=0.6 moles
the   reacting  ratio  of   nan3  to  h2  is  2:3  therefore   the  mole  of   h2  formed  is ( 0.6  x3 )/2=0.9 moles
using  the  avogadros  law
1   mole=6.02  x   10^23,   what  about  0.9  moles
=0.9  x ( 6.02  x10^23)=5.418  x 10^23

Answer 2

Sodium Azide in an air bag = 39g 
Converting the given grams in to moles, that is 1 mole = 65 grams 
Sodium Azide in moles = 0.6 
From the equation there are 2 moles of Sodium Azide and there are 3 moles of N 
Calculating the N2 in moles = (3 x 0.6)/2 = 0.9 moles of N2 
Calculating the molecular mass of N = 0.90 x 6.022 x 10^23 = 5.42 x 10^23.