What happens when (Write the balanced equation involved) –
(i) Copper is heated in air?
(ii) Aluminium oxide is reacted with hydrochloric acid?
(iii) Potassium reacts with water?
(iv) Cinnabar is heated in air?
(v) Aluminium oxide reacts with sodium hydroxide?
Answers
Answer:
1. Heated copper metal reacts with oxygen to form the black copper oxide. The copper oxide can then react with the hydrogen gas to form the copper metal and water. When the funnel is removed from the hydrogen stream, the copper was still be warm enough to be oxidized by the air again.
2. Aluminium oxide is amphoteric. ... Reaction with acids: Aluminum oxide contains oxide ions, and thus reacts with acids in the same way sodium or magnesium oxides do. Aluminum oxide reacts with hot dilute hydrochloric acid to give aluminum chloride solution.
3. When potassium is added to water, the metal melts and floats. It moves around very quickly on the surface of the water. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame.
4. cinnebar is reduced to mercury and sulpher di-oxide gas is formed.
5. Aluminum oxide react with sodium hydroxide to produce sodium aluminate and water. This reaction takes place at a temperature of 900-1100°C.