The baking soda and vinegar reaction is a classic school project because it is safe, visible, and easy to measure. Baking soda contains sodium bicarbonate, and vinegar contains acetic acid, which react to form carbon dioxide gas. The fizzing, bubbling, and balloon inflation show that a gas is being produced.
By changing one variable at a time, students can turn a fun demonstration into a controlled experiment.
Key Facts
- Balanced reaction: NaHCO3 + CH3COOH -> CH3COONa + H2O + CO2
- 1 mole of NaHCO3 reacts with 1 mole of CH3COOH to produce 1 mole of CO2.
- Moles of baking soda: n = mass / molar mass, with molar mass NaHCO3 = 84.01 g/mol.
- Moles of acetic acid in vinegar: n = M x V, where V is in liters.
- At room temperature and 1 atm, gas volume can be estimated with V = nRT / P.
- The limiting reactant controls the maximum amount of CO2 produced.
Vocabulary
- Reactant
- A starting substance that is used up during a chemical reaction.
- Product
- A substance formed by a chemical reaction.
- Limiting reactant
- The reactant that runs out first and limits how much product can form.
- Stoichiometry
- The use of balanced chemical equations to relate amounts of reactants and products.
- Controlled variable
- A factor kept the same so that a fair comparison can be made between trials.
Common Mistakes to Avoid
- Changing more than one variable at a time makes the results hard to interpret because you cannot tell which change caused the effect.
- Using balloon size as the only measurement can be misleading because balloons stretch differently and may leak gas.
- Adding extra baking soda after the vinegar is used up will not keep increasing CO2 because the acetic acid becomes the limiting reactant.
- Comparing vinegar volumes without considering concentration is incorrect because different vinegars may contain different amounts of acetic acid.
Practice Questions
- 1 A student reacts 4.20 g of NaHCO3 with excess vinegar. How many moles of CO2 can form if NaHCO3 has a molar mass of 84.01 g/mol?
- 2 A trial uses 50.0 mL of 0.83 M acetic acid. How many moles of acetic acid are present, and what is the maximum moles of CO2 that can form if baking soda is in excess?
- 3 A class tests vinegar at 10°C, 25°C, and 40°C while keeping the same amounts of reactants. Explain how temperature could affect the reaction rate and why it should not be confused with changing the total possible amount of CO2.