Reacting acids with carbonates
4 marks · NormalWrite the ionic equation for the reaction between carbonate ions and hydrogen ions.
Explain why water is formed in this reaction.
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(a) CO3^{2-}(aq) + 2H^+(aq) -> CO2(g) + H2O(l)
(b) The two hydrogen ions from the acid combine with the oxygen atom in the carbonate ion to form water.
Common mistakes: Not balancing the ionic equation; Incorrect explanation for water formation
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Marking points
A1 (a) · 2 marks · Correct ionic equation: \ce{CO3^{2-}(aq) + 2H^+(aq) -> CO2(g) + H2O(l)}
M1 (b) · 1 mark · States that H+ ions combine with O in carbonate
M2 (b) · 1 mark · Explains that this forms a molecule of water (H2O)
Worked solution
a) The ionic equation is:
b) The two hydrogen ions from the acid react with an oxygen atom in the carbonate ion to make water (H2O), with the remaining carbon and oxygen atoms forming carbon dioxide (CO2).