Objective
Show that metallic oxides are basic in nature
Materials required:
- Mg ribbon
- Red & blue litmus paper
- Test tubes
- Dropper
- Test tube holder
Procedure:
- Take about 5 cm of magnesium ribbon
- Hold magnesium ribbon with the help of a pair of tongs on the top of test tube
- Bring the free end of magnesium ribbon near the flame of the spirit lamp and let it burn
- Collect the powdery ash (formed on burning of magnesium ribbon) in the test tube
- Add small amount of water to the ash and stir it.
- Dip one by one blue and red litmus papers in the solution and observe the change in colour of litmus papers
Findings:
- There is no change in colour of blue litmus paper
- The red litmus paper turns blue
Conclusions:
- The magnesium oxide after dissolving in water shows basic character. On burning, magnesium forms magnesium oxide (ash), when this is dissolved in water it forms magnesium hydroxide (basic in nature)
- Magnesium + Oxygen (air) → Magnesium oxide
- Magnesium oxide + Water → Magnesium hydroxide
Theory:
- The oxidation or combustion of magnesium in air has long been used as a source of intense light in photography and for other photochemical reactions. The energy released in this combustion occurs as the magnesium reacts with oxygen in the air according to the equation: 2 Mg (s) + O2 (g) → 2 MgO (s) The heat of formation of magnesium oxide is -601.83 kJ/mol. When magnesium burns, approximately 10% of the energy of combustion occurs as light, a value unapproached among known transformations of energy used in the production of light.