CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry
A student adds an excess of aqueous sodium carbonate to an aqueous solution of copper(II) sulfate. A pale blue precipitate of copper(II) carbonate forms and the mixture becomes colourless.
Explain how the ionic equation for this reaction is obtained, and give the ionic equation, including state symbols.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.