1.8 Tests for Gases

Question 1

Chlorine test

Answer 1

Chlorine bleaches damp blue litmus paper, turning it white. (It may turn red for a moment first though - that’s because the chlorine dissolves in the water on the damp paper and forms hydrochloric acid, which is acidic)

Question 2

Oxygen test

Answer 2

If you put a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint.

Question 3

Carbon Dioxide test

Answer 3

Bubbling carbon dioxide through (or shaking carbon dioxide with) an aqueous solution of calcium hydroxide (known as limewater) makes the solution turn cloudy. (This happens as the Carbon Dioxide reacts with the calcium hydroxide to make calcium carbonate and water - the tiny calcium carbonate particles make it appear cloudy)

Question 4

Hydrogen test

Answer 4

If you hold a little splint at the open of a test tube containing hydrogen, you get a “squeaky pop”. (The noise comes from the hydrogen burning quickly with the oxygen in the air to form H20.)

Question 5

What safety precautions are required for testing chlorine gas?

Answer 5

• Wear a gas mask
• Do the experiment in a fume cupboard