Testing for carbonates (CO3^2-)
2 marks · NormalState the substance you would add to a sample to test for carbonate ions, and describe what you would observe if carbonate ions are present.
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Also accept: dilute hydrochloric acid; dilute sulfuric acid; dilute nitric acid; bubbles of gas; effervescence
Common mistakes: Refers to incorrect acid; Does not mention the observable change
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Marking points
M1 · 1 mark · States adding a dilute acid (e.g. hydrochloric, sulfuric, or nitric acid).
A1 · 1 mark · Describes fizzing, bubbles, or effervescence if carbonate ions are present.
Worked solution
Add a few drops of dilute hydrochloric acid to the sample. If carbonate ions are present, you will observe fizzing or bubbles of gas given off.