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Apparatus and chemicals

• Conical flask with side arm, thistle funnel, delivery tube
• 3 gas jars with lids (or test tubes with stoppers)
• Basin/trough of water
• Test-tube rack
• Calcium carbonate small pieces 3 g
• 50 cm³ of hydrochloric acid 1 mol/dm³
• Wooden Splint
• Limewater 5 cm³
• Universal indicator solution

Method

1. Carefully place the calcium carbonate into the conical flask.
2. Collect 50 cm³ of hydrochloric acid in a small beaker.
3. Connect the delivery tube and thistle funnel to the conical flask with the delivery tube in a basin of water.
4. Have three gas jars/test tubes filled with water also inverted in the basin of water.
5. Carefully pour the hydrochloric acid into the thistle funnel, wait 5 s then carefully place the first water filled gas jar/test tube over the end of the delivery tube. Allow the gas jar/test tube to fill with gas (when all of the water has been displaced).
6. Leave the gas jar/test tube inverted in the water to retain the gas.
7. Repeat step 5 until three gas jars/test tubes of gas have been collected.
8. Remove each gas jars/test tube from the water as required for the following tests.

Testing the gas

1. To the first gas jar/test tube insert a lit splint – record your observations.
2. To the second gas jar/test tube add 1 cm³ of limewater, stopper and shake – record your observations.
3. To the third gas jar/test tube add 5 drops of universal indicator, stopper and shake – record your observations. Add a little deionised water if no change observed and shake again.