Name the base formed when:
1. Sodium reacts with oxygen
2. Sodium oxide reacts with water
3. Copper oxide reacts with sulphuric acid
4. Sodium hydroxide reacts with (\H_2SO_4\)

Name the oxide of sulphur which reacts with water to give sulphuric acid.

A white amphoteric oxide reacts with sodium hydroxide to give sodium zincate and water. Name this amphoteric oxide.

A volatile acid X is formed when sodium chloride reacts with concentrated sulphuric acid. Name this volatile acid.