Question

Copper on reaction with moist air gives:

• A. Copper carbonate
• B. Copper oxide
• C. Basic copper carbonate
• D. Copper sulfate

Hint:

When copper reacts with moist air, it forms basic copper carbonate, which is responsible for the characteristic greenish layer (patina) on copper surfaces exposed to the elements over time.

Answer 1

The Correct Option is C

Step 1: Reaction of copper with air
When copper reacts with moist air (i.e., air containing water vapor and carbon dioxide), it undergoes a reaction to form basic copper carbonate. The reaction proceeds as follows: \[ \text{2Cu} + \text{O}_2 + \text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{Cu}_2\text{CO}_3\cdot\text{Cu(OH)}_2 \] This product is known as basic copper carbonate, which is a greenish-blue compound, commonly referred to as patina when it forms on copper surfaces over time. Step 2: Analyzing the other options

• Copper carbonate (CuCO₃) – This is not the direct product of copper's reaction with moist air but forms under different conditions with excess CO₂.
• Copper oxide (CuO) – This forms when copper reacts with oxygen in dry air or oxygen-rich environments.
• Copper sulfate (CuSO₄) – This is formed when copper reacts with sulfuric acid, not with moist air.

Step 3: Conclusion
The correct compound formed is basic copper carbonate, hence the correct answer is: \[ \boxed{\text{Basic copper carbonate (Cu}_2\text{CO}_3\cdot\text{Cu(OH)}_2)} \]