Here's why:
* Copper is a relatively unreactive metal. It sits below hydrogen in the reactivity series, meaning it is less reactive than hydrogen and will not readily displace hydrogen from acids.
* Alkaline solutions contain hydroxide ions (OH-). While hydroxide ions can act as oxidizing agents, they are not strong enough to oxidize copper significantly at room temperature.
However, there are some exceptions:
* Strong oxidizing agents in alkaline solutions can react with copper. For example, a solution of potassium permanganate (KMnO4) in a strong base can oxidize copper to form copper(II) oxide.
* In the presence of oxygen, copper can slowly react with alkaline solutions. This reaction is catalyzed by the presence of certain salts like sodium chloride (NaCl) and is known as atmospheric corrosion. The reaction forms a green patina on the copper surface, which is a mixture of copper(II) hydroxide and copper(II) carbonate.
* At high temperatures, copper can react with strong alkalis. For example, copper can react with molten sodium hydroxide (NaOH) to form sodium cuprate (Na2CuO2).
In summary, while copper is generally unreactive with alkaline solutions at room temperature, it can react under specific conditions involving strong oxidizing agents, oxygen, or high temperatures.
