Question

Sonali was performing a experiment in which metal X which was of reddish brown colour, when heated in the presence of oxygen it forms a black coloured compound Y which was basic in nature. When this is again heated in the presence of hydrogen gas it gives back the substance X. Identify the X and Y?

• A. X and y are Ca and Ca(OH)₂ respectively
• B. X and y are Mg and Mg(OH)₂ respectively
• C. X and y are Cu and CuO respectively
• D. None of these.

Answer 1

The correct option is C X and y are Cu and CuO respectively

Oxygen reacts with copper to form copper oxides which has black colour.
$2Cu\left(s\right)+O_2\left(g\right)\to 2CuO\left(s\right)\left(Air\right)BlackCuO+H_2\left(g\right)\to Cu+H_{2}O$
The copper (II) oxide is losing oxygen and is being reduced. The hydrogen is gaining oxygen and is being oxidized.
Here, X and are Cu and CuO respectively.