CO₂ and Limewater Test

Detecting carbon dioxide with calcium hydroxide

Gas Laws Beginner (Middle School) 20 min ~$5.00

Objective

Generate carbon dioxide gas from a carbonate-acid reaction and confirm its identity using the limewater test.

Background

When baking soda (sodium bicarbonate) reacts with vinegar (acetic acid), CO₂ gas is produced. Bubbling this gas through limewater (calcium hydroxide solution) produces a characteristic white milky precipitate of calcium carbonate, confirming the presence of CO₂.

Safety Warnings

  • Limewater is mildly irritating — avoid eye contact
  • CO₂ is an asphyxiant in large quantities — work in ventilated area

Required PPE

goggles

Materials

  • Baking soda (NaHCO₃) (10 g)
  • White vinegar (50 mL)
    5% acetic acid
  • Limewater (Ca(OH)₂ solution) (100 mL)
    Clear, saturated

Equipment

Erlenmeyer flask (250 mL) Rubber stopper with delivery tube Test tubes Rubber tubing

Procedure

1

Pour 100 mL of clear limewater into a test tube or small beaker.

2 min
2

Place 10 g of baking soda in the Erlenmeyer flask.

1 min
3

Add 50 mL of vinegar to the flask. Quickly insert the stopper with delivery tube.

2 min Vigorous effervescence
4

Direct the delivery tube into the limewater. Bubble the CO₂ through for 2-3 minutes.

3 min
5

Observe the limewater turning milky white as calcium carbonate precipitate forms.

2 min
6

Continue bubbling. If enough CO₂ passes through, the solution may turn clear again as soluble Ca(HCO₃)₂ forms.

5 min

Expected Results

The clear limewater turns milky white due to CaCO₃ precipitation: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. With excess CO₂, the milkiness clears: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂.

Cleanup

Neutralize remaining vinegar solution. Dispose of limewater down the drain. Rinse all equipment.

Details

Category
Gas Laws
Difficulty
Beginner (Middle School)
Duration
20 min
Est. Cost
$5.00
Steps
6
Materials
3

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Frequently Asked Questions

What is the objective of CO₂ and Limewater Test?
Generate carbon dioxide gas from a carbonate-acid reaction and confirm its identity using the limewater test.
How difficult is CO₂ and Limewater Test?
This experiment is rated as Beginner (Middle School). It takes approximately 20 minutes to complete.
What safety precautions are needed for CO₂ and Limewater Test?
Key safety precautions include: Limewater is mildly irritating — avoid eye contact; CO₂ is an asphyxiant in large quantities — work in ventilated area.
What materials are needed for CO₂ and Limewater Test?
The main materials required are: Baking soda (NaHCO₃), White vinegar, Limewater (Ca(OH)₂ solution).
What results should I expect from CO₂ and Limewater Test?
The clear limewater turns milky white due to CaCO₃ precipitation: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. With excess CO₂, the milkiness clears: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂.