Question

Give reason for the following: 

(a) Aluminium oxide is considered as an amphoteric oxide. 

(b) Ionic compounds conduct electricity in molten state.

Answer 1

(a) Aluminium oxide reacts with both acidic and basic substances to give neutralization reaction and hence cannot be called a true acid as well as base. Hence it is called Amphoteric oxide. 

Al₂ O₃ + 6HCl → 2AlCl₃ + 3H₂O ≫ Neutralisation Reaction with hydrochloric acid (behaves like a base) 

Al₂ O₃ + 2NaOH → 2NaAlO₂ + H₂O ≫ Neutralisation reaction with Sodium hydro oxide (behaves like an acid) 

(b) Ionic compounds are bound to each other with strong attraction force. Hence they are in solid form and their ions are not mobile. When in molten state the ions become mobile and act as carriers for charge and hence conduct electricity.