Grade 9 · CAPS

Grade 9 Acids and Base Reactions

Natural Sciences and Technology practice questions with answers

Grade 9 Acids and Base Reactions is part of the CAPS Natural Sciences and Technology curriculum, covering practical investigations into how acids react with bases and with metal carbonates. Learners work through experiments such as adding a base to an acid while monitoring pH, and reacting an acid with a metal carbonate to produce a salt, carbon dioxide and water, including how to test for and explain each observation. The practice questions below are drawn from ReClass's own question bank, based on real Grade 9 CAPS assessments, giving learners a chance to work through acid-base investigation questions in the same style they will meet in a test.

Worked example

8.2 The picture below shows an example of a situation in everyday life where neutralisation reactions are useful. The person in the picture has indigestion. 8.2.1 What, do you think, caused the indigestion?

Answer & explanation

The person could have heartburn because of eating unhealthy food or drinking fizzy cool drinks. OR Indigestion is a result of the production of too much hydrochloric acid in the stomach.

You'll also practise

  • 8.1 It was Friday the 13th and Vincent had had an unlucky day. He was stung twice by insects. At first, he was stung by a wasp, so he put some vinegar on the sting. Later he was stung by a bee, so he mixed bicarbonate of soda with water and applied it to the sting. The lucky part of the story is that Vincent was an attentive chemistry student, so he knew how to neutralise the stings. Determine which sting is acidic and which sting is basic.
  • A group of learners add sodium hydroxide solution (a base) slowly into dilute hydrochloric acid mixed with an indicator, to investigate how the pH changes. What was the aim of this investigation?
  • In an acid-base investigation, why should the apparatus and chemicals be handled with care?
  • In an investigation, sodium hydroxide solution (base) is slowly added to dilute hydrochloric acid (acid). Identify the acid and the base used.
  • What is the nature (acidic, basic or neutral) of metal carbonates?
  • Explain the general equation: acid + metal carbonate → salt + carbon dioxide + water.
  • Give the chemical formula for lime water.
  • What is observed when carbon dioxide gas is bubbled through clear lime water?
  • Sodium bicarbonate (pH 8) reacts with hydrochloric acid, producing a gas. From the values pH 1, pH 6, pH 7, pH 8 and pH 13, which pH value would you expect hydrochloric acid to have?
  • Explain why drinking sodium bicarbonate helps to relieve indigestion.
  • In the reaction between sodium bicarbonate and hydrochloric acid, identify the name of the gas that is released.
  • Describe how you would test for the gas released when sodium bicarbonate reacts with hydrochloric acid.
  • Sodium bicarbonate (NaHCO3) reacts with hydrochloric acid (HCl) to produce sodium chloride, water and carbon dioxide. Write the balanced chemical equation for this reaction.

Common mistakes

  • Forgetting that reacting an acid with a metal carbonate produces THREE products: a salt, water and carbon dioxide.
  • Not being able to explain why sodium bicarbonate (a base) relieves the effects of excess stomach acid.
  • Mixing up the acid and the base when identifying which substance is which in an investigation.

Aligned to CAPS Grade 9 Natural Sciences and Technology — Acids and Base Reactions.

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