What is the procedure for testing for carbon dioxide gas?

The procedure for testing for carbon dioxide gas involves passing the gas through limewater, which turns milky if carbon dioxide is present.

To test for carbon dioxide, you will need a test tube, a delivery tube, limewater, and a source of the gas you suspect to be carbon dioxide. The first step is to collect the gas in the test tube. This can be done by displacing water in a water-filled tube, or by directly collecting it if it's being produced by a chemical reaction.

Once you have the gas, you then pass it through limewater. Limewater is a solution of calcium hydroxide in water. It's a clear, colourless liquid when undisturbed. However, when carbon dioxide gas is bubbled through it, a chemical reaction occurs. The carbon dioxide reacts with the calcium hydroxide to form calcium carbonate, which is a white, insoluble solid. This causes the limewater to turn milky or cloudy.

This change in appearance is a positive test for carbon dioxide. If the limewater remains clear, then the gas is not carbon dioxide. It's important to note that this test is specific to carbon dioxide. Other gases, such as oxygen or nitrogen, will not cause the limewater to turn milky.

In a laboratory setting, you would typically use a delivery tube to connect the test tube containing the gas to the limewater. This allows you to safely and efficiently pass the gas through the limewater without losing any of it. The delivery tube should be inserted into the limewater just below the surface to ensure the gas bubbles through the liquid.

Remember to always handle chemicals with care and under the supervision of a qualified individual, as they can be hazardous if not handled correctly.