The reaction of metal oxide:
Metal oxide is a compound that contains metal chemically combined with oxygen. These compounds are basic in nature.
Therefore, when a metal oxide reacts with an acid, it forms a salt with water. This reaction is known as a neutralisation reaction.
Let us now see the reaction of metallic oxide with acids with the help of an experiment:  
Activity 1:
Step 1: Take a small amount of copper oxide \(CuO\) in a beaker.
Step 2: Add dilute hydrochloric acid \(HCl\) slowly while stirring.
Step 3:  Note the colour of the solution and observe the change.
Observation: The copper oxide gets dissolved and forms a blue-green solution.
Result: The blue-green colour indicates the formation of copper (II) chloride \(CuCl_2\) in the reaction between a metal oxide and acid.
The chemical reaction can be written as follows:
\(CuO + 2HCl \rightarrow CuCl_2+ H_2O\)
Therefore, the general reaction can be written as
\(Metal oxide + Acid \rightarrow Salt + Water\)
With the help of this reaction, we can conclude that metal oxide is basic in nature and, when reacted with acids, forms salt and water as in the case of a neutralisation reaction. This is the reason that metal oxide does not react with the base.
The reaction of Non-metallic oxide:
Non-metallic oxides are acidic in nature, so they react with bases the most. This reaction is similar to that of neutralisation reaction as they form salt and water.
We have seen the reaction of carbon dioxide with calcium hydroxide in the activity for acid and base on reaction with metal carbonates and metal hydrogen carbonates.
The reaction (carbon dioxide) through the lime water is as follows:
\(Ca(OH)_2 + CO_2 \rightarrow  CaCO_3 +  H_2O\)
Thus, the limewater turns milky due to the formation of calcium carbonate\(CaCO_3\).
In the above reaction, the non-metallic oxide is carbon dioxide, and the base is calcium hydroxide or lime water.
The overall reaction can be written as,
\(Calcium hydroxide + Carbon dioxide \rightarrow  Salt +  Water\)
Here in the above reaction, we know that the non-metallic oxide is acidic in nature which reacts with a base, forming salt and water as in the case of a neutralisation reaction. This is the reason that non-metal oxide does not react with acid.