# Tesla Airbag Summative

## Finding Volume

In order to create our airbag for Tesla, we needed to figure out the volume of the airbag so that we could make sure we had enough to fill the entire bag. This would help us determine the amount of vinegar and sodium carbonate that we would need to use. In order to do this, we filled our bag with water. We filled it as full as possible without having any water spilling out. Next, we poured the water from the bag into a beaker and then from the beaker into a graduated cylinder. Using this method, we determined the volume of our bag to be 270.0mL, or 0.27L. This told us how much CO2 we would need to produce in order to completely fill the airbag so that it could function properly and keep a person safe in an accident.

## Calculating the Needed Reactants

• Once we knew that we needed out reaction to yield 0.27L of CO2, we could find the correct proportions of Na2CO3 which would lead us to that amount. To do this, we first converted 0.27L to moles using PV=nRT. We used a probe to determine that the pressure was 0.81atm, and the temperature was 19.8 degrees C or 292.8K. So this got us (0.81atm)(0.27L) = n(0.0821)(292.8K). Solving this problem, we found that 0.27L of CO2 is 0.0090977616 moles.
• Next, we balanced the chemical equation to Na2CO3 + 2HC2H3O2 ---> CO2 + 2NaC2H3O2 + H2O
• To find the amount, in grams, of Na2CO3 we would need, we knew that there would be 1 mole of Na2CO3 for every 1 mole of CO2, which means that, for 0.0090977616moles of CO2, there needs to be 0.0090977616moles of Na2CO3. So we converted 0.0090977616moles into grams by multiplying it by the molar mass of Na2CO3, which is 105.988g. This told us that we would need 0.96g of Na2CO3.
• To find the amount, in mL, of HC2H3O2 that we would need, we first recognized that there are 2 moles of HC2H3O2 for every 1 mole of CO2. So, for 0.0090977616 moles of CO2, there needs to be 0.0181955232 moles of HC2H3O2. We converted this to mL by using the formula M=mol/L. This gave us 3.0M = 0.0181955232mol/L. When we did this, we got 0.00607L, or 6.07mL of HC2H3O2.

## Procedure

• First, we gathered the materials. We used a plastic bag, two plastic disposable pipets, vinegar, sodium carbonate, a graduated cylinder, a beaker, and a balance.
• We took two disposable plastic pipets and cut the long, thin part off of the end. Then we cut the remaining part of each pipet in half, disposing of the two halves that had holes in them.
• Then, we measured out 0.96g of Na2CO3 by putting an empty beaker on the balance and zeroing it out. Next, we added the Na2CO3 gradually until the balance reached 0.96g.
• Carefully, we poured the measured amount of Na2CO3 into one of the halves of the pipet. We then pushed the other half of the pipet into the half which is holding the Na2CO3, with the round part going in first, creating a capsule. We made sure that the two pieces were together tightly enough that they would not disconnect when shaken.
• Next, we poured the HC3H3O2 into the graduated cylinder until it measured 6.07mL and pourd this measured amount into the empty plastic bag.
• When it was time to test the bag, we placed the plastic capsule gently into the bag and closed it securely.
• To make the air bag go off, we simply separated the two halves of the capsule and shook the bag until it inflated.

## Questions

The theoretical volume of CO2 which should have been created in our prototype is 0.27L. When we ran our prototype, the bag was about 90% full. Because 90% of 0.27L is 0.24L, the estimated volume of CO2 we ended up creating was 0.24L. So, our percent error was 90%. Because we did not have any white powder left in our airbag after testing it, most likely the Na2CO3 was our limiting reactant because all of it was used up. This could have made it so that our airbag did not fully inflate.

Some errors that could have caused our airbag not to fill up all the way are errors in measurement. Measuring the vinegar was difficult and it was probably not at exactly 6.07 due to having to pour the vinegar into a beaker and then into the graduated cylinder. When we measured the sodium carbonate, it is possible that the balance was off. There is also the fact that transferring the sodium carbonate to the pipet and the vinegar into the bag may not have gone perfectly- some could have gotten dropped or may not have made it in.

Overall, our airbag worked pretty well. However, this airbag should not be used by Tesla as it does not fully inflate and it also does not inflate fast enough. However, with some improvements, the idea of the capsule inside the airbag could definitely be useful in creating an efficient airbag.