The hedgehog and the fox pdf

Sodium azide is very toxic. The fate of this compound when it is left in junked cars is a significant environmental concern. Because of sodium azide’s potential to harm the environ- ment, manufacturers are searching for safer, “greener” reactant chemicals for air bag infla- tion. This lab investigates the nontoxic reac- tion of sodium bicarbonate and acetic acid to produce carbon dioxide gas and a harmless salt, sodium acetate.

Materials Included in the materials kit:

6 Resealable plastic bags, 6 × 9 in

Needed from chemical kit 1:

Vinegar, white distilled, 1 pt

Baking soda (sodium bicarbonate), 15 g

Reorder Information: Replacement supplies for the Engineering a Better Air Bag investigation can be ordered from Carolina Biological Supply Company, kit 580308.

Call 800-334-5551 to order.

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Needed from the equipment kit:

Graduated cylinder, 50 mL

Electronic balance

Weighing boat

Plastic spoon

Beaker, 250 mL Thermometer

Safety Wear your safety goggles, chemical apron, and gloves at all times while conducting this investigation.

Read all the instructions for this laboratory activity before beginning. Follow the instructions closely and observe established laboratory safety practices, including the use of appropriate personal protective equipment (PPE) described in the Safety and Procedure sections.

The vinegar and baking soda are not suitable for household consumption or use. They should be considered chemicals and kept away from children and pets.

Do not eat, drink, or chew gum while performing this activity. Wash your hands with soap and water before and after performing the activity. Clean up the work area with soap and water after completing the investigation. Keep pets and children away from lab materials and equip- ment.

Preparation 1. Read the procedure. 2. Obtain all materials. 3. Select a clean work area.

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ACTIVITY

ACTIVITY 1

A Stoichiometry of Reactants and Products

Simulate air bag deployment by mixing reactants to fill a resealable plastic bag with carbon dioxide gas. The goal is to determine the exact stoichiometric amounts of sodium bicarbonate and acetic acid that will react to completely fill a sealed bag without bursting it.

1. The volume of each 6 × 9-inch resealable bag is 1.20 liters.

2. The current air pressure in inches of mercury can be found on local weather reports or by an internet search using the keywords, “air pressure for XXXXX” (where XXXXX is the local zip code).

3. Convert the air pressure from inches of mercury to the nearest 0.01 atmospheres using the following conversion (and record in Data Table 1):

4. Measure the room temperature in °C with a thermometer. Convert to Kelvin by adding 273, and record in Data Table 1 as Kelvin temperature.

5. Use the Ideal Gas Law to calculate the number of moles (n) of carbon dioxide required to fill a 6 × 9-inch bag. Record the number of moles (n) in Data Table 1.

6. Examine the reaction of the weak base, sodium bicarbonate (NaHCO3), and the weak acid found in vinegar, acetic acid (CH3COOH). The products are the aqueous

salt, sodium acetate (CH3COONa), and carbonic acid (H2CO3), an intermediate compound. This quickly breaks down into water and carbon dioxide, as shown in the following equation in bold print:

1. NaHCO3(s) + CH3COOH(aq) ➝ 2. H2CO3(aq) + CH3COONa(aq) ➝ 3. H2O(l) + CO2(g) + CH3COONa(aq)

7. In Data Table 1, write a balanced equation for only the reactants and products in bold print shown above in lines 1 and 3. Line 1 are the reactants and line 3 are the products.

8. Beginning with the moles of carbon dioxide determined in step 5 and the balanced chemical equation, calculate the grams of sodium bicarbonate reactant [MW = 84.0 g/ mol] needed to produce this number of moles of carbon dioxide. Record your results in Data Table 1.

9. The source of acetic acid is a solution of vinegar, which is 0.833 M acetic acid. Beginning with the number of moles of carbon dioxide determined in step 5 and the balanced chemical equation, calculate the volume of vinegar solution required. Record your results in Data Table 1.

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Data Table 1: Model Air Bag

Activity Data and Calculations

Volume of 6 × 9-inch bag 1.2 Liters

Room pressure in atm

Room temperature in Kelvin

Moles of CO2 required to inflate bag at room temperature and pressure

Balanced equation for the reaction of NaHCO3 and CH3COOH to produce CO2

Mass of NaHCO3 needed for the reaction (84.0 g/mol)

Volume of vinegar required (0.833 M acetic acid)

ACTIVITY 2

A Testing Model Air Bags 1. Using the balance and a weigh boat, weigh

the grams of sodium bicarbonate that was calculated in step 8 of Ac