Test for Carbon Dioxide

To identify the presence of carbon dioxide gas in a sample, you can perform a simple experiment using limewater. Here’s what you’ll need to do:

1. Prepare two test tubes, one containing the sample gas and the other containing limewater.

  • Limewater is an aqueous solution of calcium hydroxide, which is calcium oxide dissolved in water.

2. Bubble the gas sample into the limewater solution.

3. Observe the limewater solution. If the limewater turns cloudy, this indicates that the sample gas contains carbon dioxide.

The limewater turns cloudy because the carbon dioxide and calcium hydroxide react to form calcium carbonate. Calcium carbonate is an insoluble white precipitate, so all the little particles make the solution appear cloudy.

A diagram showing two test tubes. On the left, carbon dioxide gas is introduced into a test tube containing colourless limewater. An arrow points from the left tube to the right one, indicating the reaction's progression. The test tube on the right displays limewater that has turned cloudy due to the reaction with carbon dioxide gas. Both test tubes are sealed with cork stoppers and have bent glass tubes leading out from them.

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