Question

When copper powder is heated it gets coated with:
A.Black copper oxide
B.Yellow copper oxide
C.Red copper oxide
D.None of these

Answer 1

Hint: We know that copper is a metal with atomic symbol $Cu$. When any metal is heated in oxygen then they form their oxides. Like when copper is heated in air then it forms copper oxide which is black in color.

Complete step by step answer:
Oxides: Those compounds which react with oxygen (in air) then the formed molecule is known as oxides. Generally, all the metals form oxides. For example: when magnesium is heated in air (oxygen) then it forms an oxide known as magnesium oxide. Similarly when aluminium is heated in air (oxygen) then it forms an oxide known as aluminium oxide. In the same way when copper is heated in air (oxygen) it will form an oxide known as copper oxide. Now the copper oxides are of two types. The one which is red in color and the another which is black in color. Copper oxides which are red in color are those copper oxides in which the copper is in $(I)$ state. And copper oxide which are black in color are those copper oxides in which the copper is in $(II)$ state. These differ in states because of the environment given to the reaction. For example: if we heat copper in air at $300 - {800^ \circ }C$ then $CuO$ is formed which is black in color and in this oxide copper is in $(II)$oxidation state. And when this copper oxide is further heated then it forms $C{u_2}O$ which is red in color and in this oxide copper is in $(I)$ oxidation state.
Hence when copper is heated in air then black color copper oxide is formed.
So option A is correct.

Note:
Copper oxides differ in colors based on the molecular formula. As copper oxides are of two colors. One is black color if copper oxide is copper $(II)$ oxide which is $CuO$ and other is red in color when copper oxide is copper $(I)$ oxide which is $C{u_2}O$.