Chemistry
Chapter 12: Stoichiometry
Lab 14: Fizzy Drink Stoichiometry
Objectives:
Students will be able to:
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Determine molar masses, given the formula for citric acid and sodium bicarbonate.
Balance the chemical equation, given the products of a reaction between citric acid and
sodium bicarbonate.
 Calculate the moles or mass of another compound used and/or formed, given a specific
mass of a reactant.
 Determine which reactant is limiting, given initial amounts of the reactants.
 Identify common misconceptions about mass, moles, and volume, given alternative
positions.
Background:
The first man-made non-alcoholic carbonated beverage is attributed to Joseph Priestley who
accomplished the feat in 1767 (Priestly, 1772). He used chalk (calcium carbonate) and sulfuric
acid to produce carbon dioxide which was bubbled into water. Carbonated beverages had been
produced before this time, but the process used sugar and yeast to yield carbon dioxide and
alcohol through fermentation. Many different non-alcoholic carbonated beverages have been
created since including colas, phosphates, root beers, ginger ales, tonic waters, seltzer waters,
and others.
This activity uses citric acid and baking soda to produce the fizz in a beverage. Citric acid,
H3C6H5O7, is a triprotic acid with pKa values ranging from 3 to 6.4. It is highly soluble and
often used in beverages to enhance flavor and add a pleasant sour fruity taste. Baking soda
(NaHCO3) is a white powder also known as sodium bicarbonate, bicarbonate of soda, sodium
hydrogen carbonate, or sodium acid carbonate. The chemical and physical properties of baking
soda afford it a wide range of applications, including cleaning, deodorizing, buffering, and fire
extinguishing. A mole of baking soda will react with an acid to produce a mole of carbon
dioxide. In this experiment, the following reaction occurs when baking soda combines with
citric acid: H3C6H5O7 + 3NaHCO3  Na3C6H5O7 + 3H2O + 3CO2
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Chemistry
The citric acid molecule: note the three
acidic hydrogens
Materials:
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Kool-Aid® – unsweetened
Sugar
Citric Acid
Baking Soda
1 Plastic spoon
Paper baking cups (weigh boats)
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4 paper cups (3 oz)
1 Plastic Cups (16 oz)
Balances
Pitchers (2 qt)
Student worksheet
Safety:
 Sodium bicarbonate is slightly toxic if ingested in mass quantities so limit consumption.
 Dust may be irritating to the respiratory system.
 Citric acid is a severe eye irritant and may cause moderate skin irritation.
Pre-Lab Question:
What is the molar mass of citric acid, H3C6H5O7?
Molar mass of H3C6H5O7 = ____________________________
Procedures:
1. Pour approximately 1 oz. of Kool-Aid® into 4 3oz. paper cups (about 1/3 full).
Part 1:
Trial 1: Plain Kool-Aid® (Control)
2. Observe the general characteristics and taste the mixture of the first cup of Kool-Aid®.
3. Label the first cup “Control”.
4. Record observations in Data Table 1 on the student worksheet.
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Chemistry
Trial 2: Kool-Aid® and Citric Acid
5. Add 0.5g of citric acid to the second 3oz. cup of Kool-Aid® prior to making observations
and tasting.
6. Label the second cup “Citric Acid”
Trial 3: Kool-Aid® and Baking Soda
7. Add 0.5g of baking soda to the third 3oz. cup of Kool-Aid® prior to making observation
and tasting.
8. Label the third cup “Baking Soda”.
Part 2:
9. With your group, brainstorm to determine the best formula for a good tasting fizzy drink.
10. Record your tentative formula, including masses of each ingredient, in Data Table 2 on
the Student Worksheet.
11. Create the fizzy drink in the fourth cup of Kool-Aid®.
12. Taste and record observations in Data Table 2.
Part 3:
13. Calculate your recipe based on the chemical equation.
14. Fill a Dixie cup with Kool-Aid® (approximately 3oz). Pour the Kool-Aid® from the
Dixie cup into a larger cup (to prevent bubble-over of mixture).
15. Calculate the amount needed for 3oz. of water.
16. Now add your calculated amounts of citric acid (H3C6H5O7) and baking soda (NaHCO3)
in the recipe to the Kool-Aid®.
17. Mix and taste.
18. Record your recipe, with amounts, in the ingredients section of Data Table 3.
19. Record observations on Data Table 3.
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