Question

Sodium azide,NaN3,is made for use in car airbags.when this compound is heated to 300C.it rapidly decomposes into its elements.which volume of gas at room temperature and pressure,would be produced by the decomposition of one mole of sodium azide
a)24 dm3. b)36 dm3. c)48dm3. D)72 dm3

The answer is b ,but how to solve it

Answer 1

The decomposition reaction would produce solid sodium and gaseous nitrogen by the following reaction:

\[2NaN_3 \rightarrow 2Na + 3N_2\]
We can assume SATP conditions here (room temperature and ~atmospheric pressure). We start with 1 mole of NaN3, and from the chemical reaction above we can see that for however much NaN3 we start with, 1.5 times as many moles of gas (N2) are produced. Since we have 1 mole of NaN3 to start with, we end with 1.5 moles of gas. 1 mole of gas occupies 24.8 dm^3 at SATP, so 1.5 moles would occupy 24.8*1.5=37.2 dm^3 which makes B the best answer!