Question

What happens when copper vessel is exposed to moist air for long time?

Answer 1

Corrosion:

• The surface of some metals, such as iron, is corroded when they are exposed to moist air for a long period of time.
• This phenomenon is known as corrosion.

Exposure to copper with moist air

• When a copper $\left(\mathrm{Cu}\right)$ vessel is exposed to moist air for a long time, it forms a green deposit on its surface that is generally a combination of copper carbonate $\left({\mathrm{CuCO}}_3\right)$ and copper hydroxide $\left(\mathrm{Cu}{\left(\mathrm{OH}\right)}_2\right)$.
• This is referred to as copper corrosion.
• Copper corrodes due to oxidation, which occurs when oxygen in the air reacts with copper to generate oxide.
• When copper oxide combines with carbon dioxide $\left({\mathrm{CO}}_2\right)$, it becomes copper carbonate, which has a green color.

Balanced chemical reaction

• The reaction is as follows:

$\underset{\left(\mathrm{Copper}\right)}{2\mathrm{Cu}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{carbon}\mathrm{dioxide}\right)}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\left(\mathrm{Copper}\mathrm{hydroxide}\right)}{\mathrm{Cu}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Copper}\mathrm{carbonate}\right)}{{\mathrm{CuCO}}_3\left(\mathrm{s}\right)}$