How to Remove Co2 From Water

Carbon dioxide (CO2) is a gas under standard conditions and makes up 0.04 percent of the Earth's atmosphere. Plants require carbon dioxide to perform photosynthesis and animals exhale it as a waste product during respiration. CO2 is produced by a variety of industrial processes and can also be added to water to make carbonated beverages. CO2 can also be removed from water as an elementary chemistry experiment.

Difficulty: Moderate

Instructions

Things You'll Need:

• 15cm plastic tubing
• 20 CCs CO2
• 5ml limewater
• Syringe with tubing
• Test tube

1. Pour the limewater into the test tube. Limewater is a solution calcium hydroxide [Ca(OH)2] and water. Calcium hydroxide is only soluble in water and a saturated solution contains only 1.5g of calcium hydroxide per liter of water.

2. Attach the tubing to the end of the syringe. The tubing must be able to form an airtight seal on both the syringe and the nozzle of the CO2 cylinder.

3. Remove the syringe cap and fill the syringe with CO2 gas. Push the plunger all the way in and connect its tubing to the nozzle of the CO2 cylinder to make an airtight seal. Carefully crack the valve open. The CO2 gas should enter the syringe with just enough pressure to move the plunger back to the 20 CC position.

4. Place the free end of the syringe tube over the surface of the limewater and discharge at least 10 CCs of CO2. Cover the test tube with your thumb and shake vigorously. Observe the solid calcium carbonate (CaCO3) settle to the bottom of the tube as a white precipitate.

5. Examine the reaction demonstrated by the experiment. CO2 in water is removed by adding calcium hydroxide as shown by the following equation: Ca(OH)2(aq) + CO2(g) -> CaCO3(s) + H2O(l).

References

• Creighton University

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