1. Classify oxides as either acidic or basic, related to the metallic and non-metallic character of the other element in the oxide.

Oxides are compounds of metals or non-metals with oxygen.

Most metal oxides are basic oxides. Examples include calcium oxide, zinc oxide and magnesium oxide.

  • Basic oxides react with acids to form a salt and water (the basic neutralisation reaction).

Basic oxide + acid —–> salt + water

calcium oxide (basic oxide) + hydrochloric acid (acid) —> calcium chloride (salt) + water

  • Basic oxides do not react with alkalis
  • Many basic oxides do not react with water. However, those from the group I and group II in the periodic table react with water to form a metal hydroxide. An alkaline solution is formed.

Basic oxide + water ——-> metal hydroxide

barium oxide (basic oxide) + water —–> barium hydroxide (metal hydroxide)


Most non-metal oxides are acidic oxides. Examples include sulfur dioxide, carbon dioxide and silicon dioxide.

  • Acidic oxides react with alkalis to form salt and water (neutralisation again)

Acidic oxide + alkali —–> salt + water

carbon dioxide (acidic oxide) + sodium hydroxide (alkali) —> sodium carbonate (salt) + water

  • Some acidic oxides react with bases such as metal oxides when heated.

Acidic oxide + base —heat—> salt

SIlicon(IV)oxide (acidic oxide) + calcium oxide (base)  —heat—-> calcium silicate (salt)

  • Many acidic oxides react with water to form acidic solutions.

Acidic oxide + water—–> acid

sulfur trioxide (acidic oxide) + water —-> sulfuric acid (acid)


  1. Further classify some other oxides as neutral, given relevant information.

Some oxides are neither basic or acidic- they are neutral oxides. They don’t react with acids or bases. Examples of neutral oxides include nitrous oxide (N2O) and carbon monoxide (CO).



Notes submitted by Lintha

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2 thoughts on “C8.2 – Types of Oxides

  1. We did not finish learning/studying this unit in school before study leave. However, after reading the notes posted above, I understand practically everything (necessary)about the unit! I just wanted to say thank you so much for the notes, this website is truly amazing and an exam saver for students, I am very grateful. Thank you once again 🙂


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