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 O₂, it forms two types of oxides-C (black) and D (red). Identify A, B, C, D and write the balanced equation.

In this scenario, we are dealing with copper, which is the reddish-brown metal referred to as A. When copper is exposed to moist air, it reacts with oxygen and moisture to form a green layer known as copper carbonate, which is B.

Identifying the Components

• A: Copper (Cu)
• B: Copper carbonate (CuCO₃)
• C: Copper(I) oxide (Cu₂O) - black oxide
• D: Copper(II) oxide (CuO) - red oxide

Balanced Chemical Equations

The reactions can be represented by the following balanced equations:

Formation of Copper Carbonate (B)

When copper reacts with carbon dioxide and water:

2 Cu + CO₂ + H₂O → Cu₂CO₃(OH)₂

Formation of Copper(I) Oxide (C)

When copper is heated in the presence of limited oxygen:

4 Cu + O₂ → 2 Cu₂O

Formation of Copper(II) Oxide (D)

When copper is heated in excess oxygen:

2 Cu + O₂ → 2 CuO

These equations illustrate the transformations of copper under different conditions, showcasing its chemical behavior and the products formed.