A student sets up the apparatus in the figure to test the gas given off when a solid reacts with a dilute acid.
Figure: Apparatus a student set up to test the gas given off when a solid reacts with a dilute acid

Give the name of the solution used in this apparatus to identify carbon dioxide.
The limewater does not change during the reaction. Explain why. Use the figure.
Give one change the student should make to the apparatus so that the test works.
40 exam-style questions on AQA GCSE Chemistry 8.2 Identification of common gases, covering 8.2.1 Test for hydrogen, 8.2.2 Test for oxygen, 8.2.3 Test for carbon dioxide, and 8.2.4 Test for chlorine. Each one has a worked solution and a mark scheme showing where the marks go.