Designing an Airbag

Purpose

Your goal is to evaluate the reaction of sodium bicarbonate with acetic acid as a potential replacement for automobile airbags. Using your stoichiometry skills, design an airbag that will effectively fill will gas. You are to minimize the amount of excess reagents and cannot explode the bag. Important steps you will need to do include:

  • Determine the stoichiometric reagent quantities to produce the desired amount of gas
  • Engineer a mechanism to avoid initiating the reaction until you want the bag to inflate
  • Analyze your experimental airbag to improve your design for the final airbag

HC2H3O2(aq) + NaHCO3(s)  H2O(l) + CO2(g) + NaC2H3O2(aq)

Available Materials

  • Sodium bicarbonate (30 grams per group)
  • Acetic acid (300 mL per group)
  • 3 Ziploc 1 Quart bags
  • Graduated cylinders
  • Scoopula
  • Electronic balance
  • Weigh boat
  • If you need any other materials – check in with Ms. Fair

Safety Information

You must wear goggles and aprons.

Procedure

Each group will design their own procedure. To keep it simples, find the least amount of sodium bicarbonate required to react with the least amount of acetic acid so that the maximum inflation occurs. Increase or decrease the sodium bicarbonate by 0.1 gram increments at a time, and increase or decrease the acetic acid by 5 mL increments at a time.

  1. Before you begin, some things to consider:
  • What is the gas being produced when sodium bicarbonate and acetic acid combine?
  • How will you determine the approximate volume of the Ziploc bag before beginning the experiment
  • How will you get both reagents inside the bag without losing the produced gas, and keeping air out?
  • How will you determine how inflated the bag is to compare the results from one trial to the next?
  • How can you determine if more sodium bicarbonate can be reacted in the bag?
  • How can you determine if more acetic acid can be reacted in the bag?
  • Why is it important to only change one variable at a time in an experiment?
  1. Hypothesize (calculate) the mass of sodium bicarbonate needed in order to fill the bag. Hypothesize (calculate) the volume in milliliters of acetic acid needed to react with the sodium bicarbonate. We are using vinegar which contains 5% acetic acid. There are 0.833 mol of acetic acid in 1.00 L of vinegar solution.
  1. Create a procedure, materials list, and data table that will be used to test your hypothesis and have it check by Ms. Fair before beginning the experiment. Be sure to include step-by-step directions, including how you will deliver each reactant to the bag, how you will measure bag inflation, how you will alter your quantities from trial to trial to get the best airbag. Your materials list must include every tool and piece of materials list as you make changes to your design. Your data table should include the trial number, the quantities of sodium bicarbonate used, the quantities of vinegar used, the degree of inflation of the bag, and any other pertinent remarks.
  1. Once you have determined the correct ratio of reactants that completely fill the bag without bursting, write a final report that includes your hypothesis, detailed procedure, discussion of the modifications you made throughout your trials, and results. (See rubric for grading guidelines).