Lesson 5 The laboratory preparation of Oxygen

• Hydrogen peroxide dissolved in water makes a colourless solution. Hydrogen peroxide slowly decomposes to make water and the colourless gas oxygen.

  This reaction can be made much faster by adding the black solid compound, Manganese (IV) Oxide.
• Word equation for laboratory preparation of Oxygen:

  Hydrogen peroxide → water + oxygen
• Method of Preparation of Oxygen:

  1. The apparatus is set up as in the diagram with some hydrogen peroxide in the flask
  2. A spatula full of manganese (IV) oxide is added to the hydrogen peroxide.
  3. The gas is collected over water.
  4. After collecting the gas hold a glowing splint in it and note down the result.
• What is the colour of oxygen gas?

  colourless
• What is the symbol for oxygen?

  O
• What is the formula of oxygen gas?

  O2
• Oxygen gas exists as diatomic molecules. What does this mean?

  Two atoms chemically bonded together in one molecule
• Which gas forms the major part of the air?

  Nitrogen
• This gas (nitrogen) is inert. What does this mean?

  Does not react with other chemicals.
• Which gas in the air is used up when substances burn?

  Oxygen
• What three are needed for a fire?

  Fuel , Oxygen and Heat
• What is the test for:

  Carbon dioxide: will turn limewater milky white

  Oxygen: will relight a splint

  Nitrogen: it does neither of the above