Ideal Gas Airbags Lab

 

Ideal Gas Airbags Lab (Home Version and Alternative Assignment)

Airbags were mandated as a piece of safety equipment for all vehicles in 1998. All cars and trucks are required to have airbags on both driver and passenger sides. Many vehicles today include side passenger airbags. To date, the National Highway Traffic Safety Administration, NHSA, calculates that using a seatbelt and having an airbag reduces the risk of death by 61 percent. Automobile airbags are simply gas-inflated cushions. The gas that fills the bag is the result of a series of rapid chemical reactions triggered by impact. In this activity, you will simulate the process of generating the gas using a different but similar chemical reaction inside a resealable plastic sandwich bag. If you do not have the materials to do this lab and cannot obtain them, please do the alternative assignment described at the end of this document. You can use the internet to do the research /summary paragraph without needing to do the actual lab.

Purpose: 

Your mission is to generate enough gas to just fill a small resealable plastic sandwich bag with gas from the reaction between acetic acid, otherwise known as vinegar (CH3COOH) and baking soda (NaHCO3). The ideal airbag will be filled to plumpness yet not over or underinflated. Since we did not make it to our last gas law, the Ideal Gas Law. After the experiment, answer the post-lab questions. 

Materials:

White Vinegar (CH3COOH)

Baking Soda (NaHCO3)

Ziploc sandwich Bag

Something to keep the Vinegar and Baking Soda separate (balloon, Easter egg, tissue, etc.)

Measuring tools (teaspoon and cup)

Equation:

NaHCO3(s) + CH3COOH(aq)  —-> CO2(g) + H2O(l) + NaCH3CO2(aq)

Calculations: 

How much baking soda do we need to fill up the baggie? 

The Ideal Gas Law is PV = nRT, we can insert many of these values! 

P = Pressure in kPa (use STP)

V = volume in liters, so, volume of the sandwich baggie in liters. (average sandwich bag is about  V = .75 L)

T = temperature in Kelvins  (use home thermostat and convert) 

R = gas constant

n = moles of the gas, we dont know this yet but with all our other variables, we can find out! 

Calculate for the moles of gas needed to fill the sandwich bag using the ideal gas law

Convert Moles to Grams of Baking soda needed (use molar mass!)

Now that we have moles of the gas, we can calculate grams of baking soda! Basically, use the 2 teaspoons as directed in #3 of the procedure 

Procedure:

1. Go outside or at least do this in the kitchen sink.
2. Add 1/2 cup of vinegar to the bag.
3. Put 2 teaspoons of baking soda into the middle of the tissue
4. Add the baking soda to the bag without contacting the vinegar until you close the bag! Suggestions include to strategically fold the bag to keep contents separated, wrap the baking soda up in the tissue by folding the tissue around it and then add it (you can also use an Easter egg, a balloon, or whatever else you can think of to keep the baking soda and vinegar apart until the bag is sealed.)
5. You will have to work fast now partially zip the bag closed but leave enough space to add the baking soda packet. Put the tissue with the baking soda into the bag and quickly zip the bag completely closed.
6. Feel the reaction temperature trough the bag and then place the bag in the sink or down on the ground (outside) and step back. The bag will start to expand, and expand
7. Given supplies, try this experiment a couple times, adjusting the amount of baking soda you put in until you can get as close to a  perfectly full bag as possible. 
8. If you like, take a photo of your results and attach it to your paragraph submission online! 
9. Post lab Questions
10. Was this reaction exothermic or endothermic?  How do you know?
11. What was the limiting reagent in your experiment? Justify your answer with data and calculations.
12. Sketch the system of the inflated plastic bag after the reaction has finished. Label all of the species present in the bag.
13. The reaction in this activity is only a simulation for that in a real automobile airbag. Write the series of balanced chemical equations for the reaction that actually takes place in an automobile airbag. You may need to do some research, and many online resources are available. 
14. The average volume for the driver airbag has remained an average volume of 56 L over the years. Consider only the first step in the reaction written in question 4 and calculate the mass of the reactant needed to produce this volume of gas. 

Summary Paragraph/Alternative Assignment:

Research the history and chemistry of the modern airbag. Your completed work should be at least one full page and include:

1. History of the first airbag development (how they work, year of first airbag, has the chemical reactions used changed?)
2. The chemical reactions most commonly used today in airbags.
3. Similarities and differences between your airbag and a car air bag. If you didnt make an airbag, by reading the procedure you could still come up with some similarities and differences!
4. All writing in your own words!
5. Include at least two sources MLA cited.