As we know that when the exhaled air rich in carbon dioxide is blown from mouth into test tube. The lime water turns milky on passing CO₂ gas into it due to formation of insoluble calcium carbonate (CaCO3). As it ...

Copper gets a green coating due to the formation of a mixture of copper carbonate (CuCO₃) and copper hydroxide when it reacts with carbon dioxide gas and the moisture present in air. This is called tarnishing of copper.