Question

A reddish brown metal A, when exposed to moist air, forms a green layer B. When A is heated at different temperatures in the presence of ${{{O}}_2}$, it forms two types of oxides-C (black) and D (red). Identify A, B, C, D and write the balanced equation.

Answer 1

Hint: Metals are the solid materials which are elements, compound or alloys. There is an electrostatic force of attraction between the positive metal ions and delocalized electrons. All metals combining with oxygen to form metal oxides.

Complete step by step answer:
Generally metals have the following properties:
1.Malleability-beaten into thin sheets with hammer
2.Ductility-drawn into wires
3.Good conductors of heat and electricity
4.Lustrous
5.Sonorous
6.High density
Metal works with positive valency and oxygen with valency $ - 2$. The metal in reddish brown color is copper. When copper is reacted with moist air, it gives green color at the surface of the copper metal. This is due to corrosion of copper. The moist air contains water, carbon dioxide and oxygen. The complete balanced chemical equation is given below:
${{2C}}{{{u}}_{\left( {{s}} \right)}} + {{{H}}_2}{{{O}}_{\left( {{l}} \right)}} + {{C}}{{{O}}_{2\left( {{g}} \right)}} + {{{O}}_{2\left( {{g}} \right)}} \to {{CuC}}{{{O}}_{3\left( {{s}} \right)}} + {{Cu}}{\left( {{{OH}}} \right)_{2\left( {{{aq}}} \right)}}$
The green color is due to the mixture of ${{CuC}}{{{O}}_3}$ and ${{Cu}}{\left( {{{OH}}} \right)_2}$.
Copper when reacted to ${{{O}}_2}$ cuprous oxide and cupric oxide is formed. The main difference between cuprous and cupric oxide is that cuprous oxide has oxidation state $ + 1$ and cupric oxide has oxidation state $ + 2$. The chemical formula of cuprous oxide is ${{C}}{{{u}}_2}{{O}}$ and that of cupric oxide is ${{CuO}}$. Cuprous oxide is red in color while cupric oxide is black in color.
The complete chemical balanced equation of formation of cupric oxide is given below:
${{2Cu}} + {{{O}}_2} \to 2{{CuO}}$
                          black
The complete chemical balanced equation of formation of cuprous oxide is given below:
${{4Cu}} + {{{O}}_2} \to 2{{C}}{{{u}}_2}{{O}}$
                           Red
Hence the compounds A, B, C, D are ${{Cu}},{{CuC}}{{{O}}_3},{{CuO}},{{C}}{{{u}}_2}{{O}}$ respectively.

Note: In the formation of ${{Cu}}$ to ${{CuO}}$, the electronic configuration of copper changed from $\left[ {{{Ar}}} \right]3{{{d}}^{10}}4{{{s}}^1}$ to $\left[ {{{Ar}}} \right]3{{{d}}^{10}}4{{{s}}^0}$. This is similar in the formation of ${{Cu}}$ to ${{C}}{{{u}}_2}{{O}}$. Both ${{CuO}}$ and ${{C}}{{{u}}_2}{{O}}$ are stable compounds.