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Amphoteric Oxide

An amphoteric oxide is an oxide that reacts with both acids and bases.

In one line: Two-sided reaction means amphoteric nature.

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Understand it

Amphoteric oxides show a special nature because they can behave as acidic or basic oxides depending on the substance they react with. Zinc oxide and aluminium oxide are important examples. This property is often tested using reaction comparison questions.

Example

Zinc oxide reacts with both hydrochloric acid and sodium hydroxide.

Rule to remember

Rule: amphoteric oxides react with acids as well as bases; common examples are ZnO and Al2O3.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

If zinc oxide reacts with dilute HCl to form zinc chloride and also reacts with NaOH to form sodium zincate, the oxide is amphoteric.

Method you can reuse

  1. 1Check whether the oxide reacts with acid.
  2. 2Check whether it also reacts with base.
  3. 3If both happen, write amphoteric.
  4. 4Quote one example such as ZnO or Al2O3.

Visual tip

A two-arrow comparison diagram showing one oxide reacting with acid and base is enough for quick revision.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

A white oxide dissolves in both dilute hydrochloric acid and sodium hydroxide solution. What type of oxide is it?

Think first, then show answer
It is amphoteric, because it reacts with both acids and bases.

Common wrong answer

Basic oxide is the common wrong answer because many students remember only the metal-oxide rule and forget exceptions.

Don't mix this up

Students often call every metal oxide basic, but some oxides like zinc oxide and aluminium oxide are amphoteric.

Exam tip

If an oxide reacts with both acid and base, amphoteric is the correct idea.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Exam questions may ask for the nature of zinc oxide or aluminium oxide, or ask why they are different from ordinary basic oxides.
  1. 1

    Enough for 1 mark

    An amphoteric oxide is an oxide that reacts with both acids and bases.

  2. 2

    Add for 2 marks

    Example: Zinc oxide reacts with both hydrochloric acid and sodium hydroxide.

  3. 3

    Add for 3 marks

    Amphoteric oxides show a special nature because they can behave as acidic or basic oxides depending on the substance they react with.

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