AQA GCSE Chemistry

Revision Notes

8.3.3 Carbonates

Test for Carbonates

  • Carbonates all contain the carbonate ion, CO32-
  • The test for this ion involves adding dilute acid and testing the gas released
  • If a carbonate compound is present then effervescence should be seen and the gas produced is CO2 which forms a white precipitate of calcium carbonate when bubbled through limewater:

CO32- (aq) + 2H+ (aq) → CO2 (g) + H2O (l)

CO2 (g) + Ca(OH)2 (aq) → CaCO3(s) + H2O(l)

Test for Carbon Dioxide, IGCSE & GCSE Chemistry revision notes

Limewater turns milky in the presence of CO2 caused by formation of insoluble calcium carbonate

Exam Tip

You’ll need to connect the test tube of the suspected ion to the test tube of limewater quickly so none of the CO2 escapes.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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