Question

A shiny brown coloured metal ‘X’ on heating in air becomes black in colour. The element 'X' and black coloured compound are ___ and ___ respectively.

• A. copper, copper oxide
• B. silver, silver oxide
• C. magnesium, magnesium oxide
• D. iron, iron oxide
  

Answer 1

The correct option is A copper, copper oxide

The colour of copper element is shiny brown. When copper is heated in air it turns black due to the formation of copper oxide layer on it.
$2\text{Cu}\text{(s)}+{\text{O}}_2\text{(g)}\to 2\text{CuO}\text{(s)}$
Hence, element 'X' is copper and the black coloured compound is copper oxide.