Describe what is observed when dilute hydrochloric acid is added to sodium carbonate, and state two other types of substance that react with acids in a similar way to sodium carbonate.

Cambridge International IGCSE Chemistry (0620) — 7.1 The characteristic properties of acids and bases · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Effervescence (bubbles) is seen when dilute HCl is added to Na₂CO₃.
The reaction produces carbon dioxide gas.
Other substances that react with acids in the same way are metal oxides (e.g. CaO) and metals (e.g. Zn).

Examiner tips

  • Use the word ‘effervescence’ or ‘bubbles’ to show you know the observation. Show the reaction produces CO₂. Give two examples that match the mark scheme: a metal oxide and a metal. Keep the answer concise – 4 marks only.
  • common_mistakes
  • :
  • Writing ‘fizzing’ instead of ‘effervescence’. Omitting the CO₂ gas. Listing only one type of substance (e.g. only metals) instead of two. Using vague terms like ‘reactive substances’ without specifying metal oxides or metals.

Mark scheme (4 marks)

  1. Effervescence / bubbles / fizzing is observed
  2. Carbon dioxide gas is produced
  3. Metal oxides (or metal hydroxides) also react with acids
  4. Metals also react with acids

Key terms in this question

acid · carbonate

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