TOPIC: ATMOSPHERE AND COMBUSTION

SUBTOPIC:

 

TEST FOR OXYGEN

When a glowing splint is placed in a jar containing Oxygen the glowing splint relights

USES OF OXYGEN

  • Used in respiration in living organisms
  • Oxygen is used in manufacture of steel
  • Liquid oxygen is used as fuel in space rockets
  • The mixture of acetylene (ethyne) and oxygen burn to produce a very hot flame used in welding and metal cutting

     

    PHYSICAL PROPERTIES OF OXYGEN

  • It is colourless, odourless and tasteless gas
  • Slightly soluble in cold water
  • Neutral to litmus

     

    CHEMICAL PROPERTIES OF OXYGEN

  1. Reaction with metals

    Reaction of oxygen with metals form oxides, most of them are basic in character. The solutions of these oxides in water will be alkaline (Turn Red litmus paper blue), thus have a PH greater than 7.

     

  2. Reaction of oxygen with sodium
  • Sodium burns in Oxygen with a bright yellow flame forming a yellow solid of sodium peroxide

     

    2Na(s) + O2(g) Na2O2(s)

     

When the product (sodium peroxide) is added to water and shaken, it dissolves with effervescence of a colourless gas (Oxygen) forming a colourless solution of sodium hydroxide. The solution turns red litmus paper blue implying sodium burns to form a white solid of sodium oxide.

    2Na2O2(s) + 2H2O(l) 4NaOH(aq) + O2(g)

 

  • However in limited oxygen supply, sodium burns to form a white solid of sodium oxide.

     

    4Na(S) + O2(g) 2Na2O(s)

  1. Sodium metal was burnt in excess oxygen.

    a(i) State what was observed

    (ii) Write the equation for the reaction that took place

    b) The product formed from (a) above was dissolved in water.

    1. State what was observed
    2. Write equation for the reaction that took place between the product from 1a) and water
    3. The solution formed was

     

  2. When water was added to solid Y, a gas that relights a glowing splint was given off.

    a(i) Name solid Y

    (ii) Write the equation for the reaction that took place.

    b(i) State what would be observed if some red litmus were dropped in the resulting solution in a(ii) above.

    (ii) State any three uses of oxygen gas


     

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