Question

When an airbag explodes, there are 3 different types of reactions that occur. Sodium azide produces nitrogen gas but there is a bi-product of Na. Na is very reactive and must be neutralized. For this, potassium nitrate is used. This creates two further compounds, sodium oxide and potassium oxide, which must be neutralized by silicon dioxide.

Chemical reactions:

1. Sodium Azide is ignited. Nitrogen gas fills nylon bag at 150-250 miles/hr

NaN₃ ? N₂ + Na

2. Reaction with potassium nitrate (1st stage to eliminating dangerous by-products)

Na + KNO₃ ? N₂ + Na₂O + K₂O

3. Reaction with sodium and potassium oxide to form silicate glass (2nd stage to eliminating dangerous by-products)

K₂O + SiO₂ ? K₄SiO₄ Na₂O + SiO₂ ? Na₄SiO₄

A typical 60L airbag requires 5.82 moles of nitrogen gas to fill it up. A manufacturer puts 65.0 g of SiO₂ in an airbag. Using stoichiometry, we are going to find out how many grams of SiO₂ is required to completely neutralize the dangerous by-products of the airbag reaction & conclude whether 65.0 g is enough.

PART A:

1. Use stoichiometry to calculate the number of moles of sodium produced by the first reaction if 378.3g of NaN₃ is used. SHOW ALL YOUR WORK & BE NEAT!! Use significant figures where appropriate.

NaN₃? N₂+Na

PART B:

2. Sodium is very reactive and must be neutralized. Using the number of moles of Na produced from the first reaction, calculate using stoichiometry. SHOW ALL YOUR WORK & BE NEAT!! Use significant figures where appropriate.

Na + KNO3 ? N2 + Na2O + K2O

2a) how many moles of Na2O are created?

2b) how many moles of K2O are created?

PART 3 ; SHOW ALL YOUR WORK AND BE NEAT.

The products Na₂O + K₂O are also dangerous, and must further be neutralized by SiO₂ to produce K₄SiO₄ and Na₄SiO₄

3a) What mass of SiO₂ would be required in order to fully react with all of the of K₂O from question (2)?

K₂O + SiO2 ? K₄SiO₄

3b) What mass of SiO₂ would be required in order to fully react with all of the of Na₂O from question (2)

Na2O + SiO2 ? Na₄SiO₄

4. How much SiO₂ is needed in total? Was 65 g of SiO₂ enough?

Answer 1

1. The balanced reaction is : 2 NaN₃ = 2 Na + 3 N₂

Molar mass of NaN₃ = 65 g/ mole

So, 378.3g of NaN₃ contains (378.3 g/ 65 g/ mole) = 5.82 moles of NaN₃

From the reaction stoichiometry, we get: Moles of Na produced/ Moles of NaN₃ reacted = 2/2

So, Moles of Na produced = Moles of NaN₃ reacted = 5.82 mole

2. The balanced equation is : 2 Na + 2 KNO₃ = Na₂O + K₂O + 2 NO₂

(a) From the stoiciometry we get:

Moles of Na₂O produced/ Moles of Na reacted = 1/2

So, Moles of Na2O produced in the reaction = (1/2) * Moles of Na reacted = (1/2) * 5.82 mole = 2.91 mole

(b) From the stoiciometry we get:

Moles of K₂O produced/ Moles of Na reacted = 1/2

So, Moles of K₂O produced in the reaction = (1/2) * Moles of Na reacted = (1/2) * 5.82 mole = 2.91 mole

3.

(a) The balanced reaction is : 2 K₂O + SiO2 = K₄SiO₄

Moles of SiO₂ reacted / Moles of K₂O reacted = 1/2

So, Moles of SiO₂ reacted = (1/2) * Moles of K₂O reacted = (1/2) * 2.91 mole = 1.455 mole

Mass of SiO2 needed = moles of SiO₂ * Molar mass of SiO₂ = 1.455 mole * 60.08 g/ mole = 87.41 g

(b) The balanced reaction is : 2 Na₂O + SiO2 = K₄SiO₄

Moles of SiO₂ reacted / Moles of _Na2O reacted = 1/2

So, Moles of SiO₂ reacted = (1/2) * Moles of na₂O reacted = (1/2) * 2.91 mole = 1.455 mole

Mass of SiO2 needed = moles of SiO₂ * Molar mass of SiO₂ = 1.455 mole * 60.08 g/ mole = 87.41 g

4. Total SiO₂ needed = 87.41 g + 87.41 g = 174.82 g

So, 65 g of SiO₂ is not sufficient.