Question

When a black metal compound XO is heated with a colourless gas Y₂, then metal X and another compound Y₂O are formed. Metal X is red-brown in colour which does not react with dilute acids at all. Gas Y₂ can be prepared by the action of a dilute acid on any active metal. The compound Y₂O is a liquid at room temperature which can turn anhydrous copper sulphate blue.

1. What do you think is metal X?
2. What could be gas Y₂?
3. What is compound XO?
4. What is compound Y₂O?
5. Write the chemical equation of the reaction which takes place on heating XO with Y₂.
6. What type of chemical reaction is illustrated in the above equation?

Answer 1

1. Metal X is copper. It is a red-brown metal that is less reactive than hydrogen and does not react with dilute acids.
2. Gas Y₂ is hydrogen (H₂). It is a colourless gas produced by reacting active metals (such as zinc) with dilute acids.
3. The compound XO is copper(II) oxide (CuO). It is a black copper compound.
4. The compound Y₂O is water (H₂O). Water is a liquid at room temperature that turns white anhydrous copper sulphate blue (due to hydration).
5. \[\ce{CuO + H2 -> Cu + H2O}\]
6. This is a redox reaction or a displacement reaction. Hydrogen reduces copper(II) oxide to copper while itself getting oxidised to water.