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Excess dilute sulfuric acid is added to a solid sample of a copper compound - Edexcel - GCSE Chemistry - Question 4 - 2017 - Paper 1
Question 4
Excess dilute sulfuric acid is added to a solid sample of a copper compound. A gas is given off and a blue solution is formed. (i) The gas turns limewater cloudy. ... show full transcript
Worked Solution & Example Answer:Excess dilute sulfuric acid is added to a solid sample of a copper compound - Edexcel - GCSE Chemistry - Question 4 - 2017 - Paper 1
Step 1
Explain how this result is used to identify the anion in the copper compound.
Answer
The gas produced when dilute sulfuric acid reacts with the copper compound is most likely carbon dioxide (CO₂). When CO₂ is bubbled through limewater (a dilute solution of calcium hydroxide), it reacts with calcium hydroxide to form calcium carbonate, which is insoluble and causes the limewater to turn cloudy. This cloudiness indicates the presence of carbonate ions (CO₃²⁻) in the copper compound.
Step 2
Step 3
Write the ionic equation, including state symbols, for this reaction.
Answer
The ionic equation for the reaction between barium chloride and the blue solution containing sulfate ions is:
ightarrow ext{BaSO}_4(s)$$ This indicates that barium ions (Ba²⁺) react with sulfate ions (SO₄²⁻) to form barium sulfate, which precipitates out of solution as a solid.