8.3 Tests for Gases

• What is the purpose of today's video?

  To show how to test for four gases: chlorine, oxygen, hydrogen, and carbon dioxide
• What is the first step in testing for chlorine?

  Fill a test tube with the sample gas suspected to contain chlorine
• What should you do with the blue litmus paper when testing for chlorine?

  Dampen it before inserting it into the test tube
• What happens to the blue litmus paper if chlorine is present?

  It turns from blue to white
• Why might the blue litmus paper briefly turn red before turning white?

  Chlorine dissolves in water on the damp paper, forming hydrochloric acid
• What safety precaution should be taken when testing for chlorine?

  Wear a mask or conduct the experiment in a fume cupboard
• What is used to test for oxygen?

  A glowing splint
• What happens to a glowing splint when it is placed in oxygen?

  It relights
• What is the test for hydrogen?

  A burning splint produces a squeaky pop when near hydrogen
• What is the reaction that occurs when hydrogen burns?

  Hydrogen burns with oxygen to form water
• What is used to test for carbon dioxide?

  An aqueous solution of calcium hydroxide, also known as lime water
• What happens when carbon dioxide is bubbled through lime water?

  The solution goes cloudy
• Why does lime water go cloudy when carbon dioxide is present?

  Calcium carbonate is formed, which is a solid
• What are the tests for the four gases: chlorine, oxygen, hydrogen, and carbon dioxide?

  • Chlorine: Blue litmus paper turns white
  • Oxygen: Glowing splint relights
  • Hydrogen: Squeaky pop with a lit splint
  • Carbon dioxide: Lime water goes cloudy
• What is the chemical reaction that occurs when carbon dioxide reacts with calcium hydroxide?

  Carbon dioxide reacts with calcium hydroxide to form calcium carbonate and water
• What is the appearance of calcium carbonate in solution?

  It appears cloudy
• What is the final recap of the tests for the four gases?

  Chlorine turns litmus paper white, oxygen relights a glowing splint, hydrogen gives a squeaky pop, and carbon dioxide makes lime water cloudy