Non-metal oxides act like acids

The idea

Non-metallic oxides react with bases to give a salt and water, like an acid does, so non-metallic oxides are acidic in nature.

Milky lime water

Lime water, calcium hydroxide, is a base. When carbon dioxide is passed through it, it turns milky because a white solid forms.

What kind of reaction gives a salt and water with a base?

• An acid reacting with it
• A metal reacting with it
• Heating it

Gas meets base

The gas from a carbonate meets lime water.

Now compare it with an acid meeting the same base.

The oxide is the acid’s twin

Non-metallic oxides react with bases to give a salt and water, like an acid does. So non-metallic oxides are acidic in nature.

Metal oxides are basic. Non-metal oxides are acidic.

• Reactants | Products
• Acid + base | 2HCl + Ca(OH)₂ | CaCl₂ + 2H₂O
• Non-metal oxide + base | CO₂ + Ca(OH)₂ | CaCO₃ + H₂O

Notes

Non-metallic oxides react with bases to give a salt and water, like an acid does, so non-metallic oxides are acidic in nature.

Check yourself

CO₂ meets lime water. What forms?

Non-metal oxide + Base → ?

Why are non-metallic oxides called acidic?

Match: which oxides are basic?

• A salt (CaCO₃) and water — correct. Yes! Just as an acid gives with a base.
• Hydrogen gas. No metal is involved here, so no hydrogen.
• Nothing forms. The lime water turns milky: a white salt forms.
• Salt + hydrogen. That is metal + acid.
• Salt + water — correct. Yes!
• Metal + water. No metal forms. A salt and water do.
• They are always sour. We never taste chemicals. The idea is how they react with a base.
• They react with acids. Metal oxides react with acids. Non-metal oxides react with bases.
• They react with bases to give salt and water, as an acid does — correct. Yes!
• Metallic oxides — correct. Yes! Non-metallic oxides are acidic.
• Non-metallic oxides. These are the acidic oxides.
• All oxides. Metal oxides are basic and non-metal oxides are acidic.