Experiment 13 Gas laws and Air bags Airbags in cars are devices that inflate ver

Question

Experiment 13 Gas laws and Air bags

Airbags in cars are devices that inflate very rapidly (in about 30 milliseconds) when there is a collision, creating a cushion that deflates slowly and reduces the impact of the collision on the driver or the passenger. The bag is inflacted by a gas, which is generated by the heating of sodium azide (NaN_3) to about 300 degree C, causing it to decompose into sodium metal and nitrogen gas. Complete and balance the equation for this reaction, indicating the states of the reactant (NaN_3(s)) and products (Na(s) and N_2(g)). Enough nitrogen must be generated in the bag to create a total pressure of 3.10 atm, which then drops as the bag slowly deflates. Assuming the volume of the bag is 58.0 L and the temperature in the car is 25 degree C, calculate the molar quantity of N_2 that must be generated. What molar quantity of sodium azide is required to generate this much nitrogen? What mass of sodium azide is required? The sodium metal produced in the reaction is highly reactive and potentially explosive, so it is removed in a reaction with excess KNO_3(s) that produces K_2O(s) and Na_2O(s) and additional nitrogen. Write a balanced equation for this process, showing the states of the reactants and products.

Explanation / Answer

a) the balanced reaction is

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

we know that

for ideal gas

PV = nRT

given

P = 3.1

V = 58

T = 25 C = 298 K

using these values

3.1 x 58 = n x 0.0821 x 298

n = 7.35

so

7.35 moles of N2 must be generated

now

consider the reaction

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

we can see that

moles of N2 produced = 1.5 x moles of NaN3

so

7.35 = 1.5 x moles of NaN3

moles of NaN3 = 4.9

so

4.9 moles of sodium azide is required

now

mass = moles x molar mass

so

mass of NaN3 = 4.9 x 65

mass of NaN3 = 318.5

so

318.5 grams of NaN3 is required

the reaction is

10 Na + 2 KN03 --> K20 + 5 Na20 + N2

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