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Question
A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black-colored compound formed.
Solution 1
X’ is copper (Cu) and the black-coloured compound formed is copper oxide (CuO). The equation of the reaction involved on heating copper is given below.
\[\ce{2Cu + O2 ->[Heat] 2CuO}\]
Solution 2
The shiny brown-colored element is the copper metal (Cu). When the metal is heated in the air, it reacts with the atmospheric oxygen to form copper oxide. Hence, the black-colored compound is copper oxide, (CuO).
\[\ce{2Cu_{(s)} + O2_{(g)} ->[\Delta] 2CuO_{(s)}}\]
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