How to make an airbag with baking soda and vinegar

CHEMISTRY

Engineering a Better Air Bag Investigation Manual

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ENGINEERING A BETTER AIR BAG

Table of Contents

2 Overview 2 Objectives 3 Time Requirements 3 Background 4 Materials 5 Safety 5 Preparation 6 Activity 1 7 Activity 2 8 Activity 3 10 Disposal and Cleanup

Overview This investigation is a chemical engineering challenge. The task is to investigate a less expensive and less toxic chemical air bag system for the automobile industry. An air bag restraint system will be modeled through a series of steps. First, the quantity in moles of carbon dioxide required to fill a model air bag at room temperature and pressure will be determined using the Ideal Gas Law. Second, the amounts of sodium bicarbonate and acetic acid reactants required to produce a sufficient volume of carbon dioxide to fill the model air bag without bursting it will be calcu- lated. Third, the reaction will be performed to test the inflation of the prototype model air bag with the predicted reactants. The final step involves scale-up and calculation of the reactant quantities required to produce enough carbon dioxide to fill driver-side and passenger-side air bags at room temperature and pressure.

Objectives • Determine the volume of a scale model air bag in liters. • Apply the Ideal Gas Law to calculate the moles of CO2 produced

in a reaction. • Calculate the stoichiometric amounts of reactants required to

produce a specific quantity of product. • Assess reactant amounts by mixing and observing the inflation

of the model air bag.

Key Personal protective equipment (PPE)

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Time Requirements Preparation 10 minutes Activity 1: Stoichiometry of

Reactants and Products 20 minutes Activity 2: Testing Model Air Bags 30 minutes Activity 3: Amount of CO2 for Full-

Size Air Bags 10 minutes

Background This lab illustrates how stoichiometry and the Ideal Gas Law can be used to predict the moles of gas needed to fill a model of an automo- bile air bag and how to scale up to predict the number of moles needed to fill full-size air bags.

Stoichiometry is the quantitative study of a chemical reaction and is based upon the coef- ficients of a balanced chemical equation. Coef- ficients represent the molar ratios of reactants to products. These ratios predict the number of moles of reactant needed to produce a given number of moles of product. These molar amounts can be converted into grams for solids or into liters for gases at given temperatures and pressures.

The Ideal Gas Law shows the relationship of all four variables for gases in one equation. That equation is PV = nRT, where P represents pres- sure (in atmospheres [atm]), V represents volume (in liters), n represents the number of moles, R represents the gas law constant (0.0821 L-atm/ mole·K), and T represents temperature (in degrees Kelvin).

Air bags in automobiles activate when an accel- erometer in a microchip senses an impact force equivalent to hitting a wall at a speed of 10–15 miles per hour. The accelerometer closes a switch that ignites a charge, causing a pellet of sodium azide (NaN3) to explode. This explosion releases sodium metal and harmless nitrogen gas that inflate the bag. The reaction is shown in the following equation:

2NaN3(s) ➝ 2Na(s) + 3N2(g)

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ENGINEERING A BETTER AIR BAG

Background continued The sodium metal produced is highly reactive and will react violently with water. Therefore, iron oxide (Fe2O3) is placed in the compartment along with the sodium azide. The sodium metal produced by the inflation reaction in turn reacts with the iron oxide to produce harmless sodium oxide (Na2O) and iron (Fe). Talcum powder or cornstarch is also released during the inflation. These substances keep the air bag pliable and lubricated during storage.