Name: Empower Yourself
Chemistry AEmpower Your Community
Date:Empower Your World
Period:
Chemical Reactions: Actual and Theoretical Yields
In this experiment you will examine the reaction between baking soda and vinegar. The baking soda is sodium bicarbonate, NaHCO3.Vinegar is a 5% solution of acetic acid, HC2H3O2, in water. The products of the reaction are water, H2O, carbon dioxide, CO2, and sodium acetate, NaC2H3O2. The reaction you are working with is shown here. You will collect the carbon dioxide gas and figure the moles of gas produced from the ideal gas equation and your data.
NaHCO3 (s) + HC2H3O2 H2O (l) + CO2 (g) + NaC2H3O2 (aq)
You will measure the amount of baking soda used. You will collect and measure the quantity of carbon dioxide formed. You will be able to calculate the % yield for the reaction by comparing the actual moles of carbon dioxide collected with the predicted moles from the mol ratio in the equation.
Please read entire procedure before you begin the experiment.
You will need to use the following.
3 Ziploc bags, 1-gallon size / Kitchen sinkEmpty 2-L soda bottle / Long pin like a hat pin or corsage pin to make hole in bag
Measuring spoon, 1 teaspoon size / Baking soda
Measuring cup, 1/2 Cup size / Plastic wrap like Saran Wrap
Large measuring cup marked in milliliters / Regular vinegar, 5% acetic acid, 2 cups
Procedure:
1. Obtain a container that is filled with water. Bring it back to your lab workstation.
2. Obtain a sheet of plastic wrap and cut it in a square that is 6 by 6 inches.
3. Measure 1 teaspoon of baking soda and place the baking soda in the center of your piece of plastic wrap. Exactly 1 teaspoon of baking soda has a mass of 5.7 grams. Fold the bottom and side edges of the plastic and wrap it loosely around the baking soda. Don’t wrap it so tight that you won’t be able to unwrap it latter.
4. Obtain a 2 L bottle with the top cut off. Find the total volume of your cut-off bottle in milliliters. Do this by measuring the water needed to fill the bottle by filling a graduated cylinder with water and calculating the amount it takes to fill the 2 L bottle. Fill your cut-off 2-L bottle to the very top. Copy this into your data table.
5. Place your palm firmly over the opening of your 2-L bottle full of water and "upend" the bottle in the tub of water. Lower your hand and the open end of the bottle into the water in the tub of water. Make sure that the bottle's opening is below the water level in the tub of water before you remove your palm. This will keep the water in the bottle. Have one table member always holding onto this bottle from this point on.
6. Measure out ½ cup of vinegar and pour it into a 1-gallon Ziploc bag. Place your loosely-wrapped packet of baking soda in the upper part of the Ziploc bag. Eliminate as much air from the bag as possible and close it with as little air in the bag as possible. Keep the vinegar and bag of baking soda as far apart as possible.
7. With permanent marker, draw a small circle on the bottom corner where you don’t have vinegar (you should have the vinegar contained in a single corner). Poke a hole inside the circle in the top layer of bag(away from the vinegar pool).
8. Grasp the corner with the hole in it and push that corner of the plastic bag up into the submerged opening in the 2-L bottle. The bag corner needs to be about 1/2 inch to 1 inch up into the bottle, but should not close up the opening in the bottle. You have to leave space for the water to exit from the bottle when the CO2 comes in.
9.Manipulate the packet of baking soda inside the Ziploc bag so that it comes open and mixes with the vinegar. The vinegar and baking soda should generate bubbles of CO2. You may want to shake or rock the bag and contents. Be sure all the baking soda comes out of the plastic wrap and gets mixed with the vinegar.
10. Your Ziploc bag may puff up with CO2 gas from the reaction. The gas is supposed to be squeezed out through the corner opening and into the 2-liter bottle.Catch the bubbles of CO2 in your 2-L bottle. As the CO2 is trapped in the bottle, it will push the water out. This is known as "displacing the water." Be sure the plastic bag is not completely blocking or covering the opening of your bottle.Force as much CO2 out of your Ziploc bag and into the bottle as you can. You want to finish the experiment with as little CO2 left in the bag as possible.
11. When you have all the CO2 out of the bag and trapped in your bottle, place your palm tightly against the opening of the bottle and turn the bottle "right-side-up". You are going to measure the volume of CO2 by finding the volume of water "missing" from the bottle.Pour the water that remained in your bottle into your large measuring cup; measure this water volume in milliliters. Subtract this number from the total volume of water your bottle will hold. This difference is the volume of CO2 that you trapped in the bottle.
Calculate the moles of carbon dioxide
1. Calculate the number of moles of NaHCO3 in 5.7 g of NaCO3. Remember, when going from grams to moles you divide by the molar mass.
2. Using the balanced equation calculate the number of moles of CO2 that will be produced from 5.7 g of NaHCO3. This is the theoretical yield of CO2
3. Change the volume of CO2 trapped in your bottle from mL to L. Then use the Ideal Gas Law (PV=nRT) to calculate the number of moles (n in the equation) of CO2 trapped in your bottle. This in the actual yield of CO2. Assume P = 1.0 atm and that T = 293 K. The gas constant, R, is 0.0821 liter-atm/mole-K. You need to calculate V.
PV = nRT
or
n=PV/RT
4. Calculate the % yield of CO2
Results
Table 1: Data from Stoichiometry Lab
Water Used to fill plastic bottle (mL)Volume of H2O left in bottle after collecting CO2 (mL)
Mass of Baking Soda Used (g)
Table 2: Calculations for Stoichiometry Lab
Moles of baking soda (NaHCO3) usedTheoretical Yield – Moles of CO2 that can be made from initial moles of NaHCO3 (mole)
Volume of CO2 Trapped in Bottle (mL)
Volume of CO2 Trapped in Bottle (L)
Actual Yield – Moles of CO2 Trapped in Bottle (mole)
Percent Yield (%)
LABS AND PROJECTS