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. Explain how this result is used to identify the anion in the copper compound. (ii) When sodium hydroxide solution is added to the blue solution, a pale blue precipitate is formed. Give the name or the formula of the pale blue precipitate. (iii) The blue solution contains sulfate ions. Barium chloride solution is added to this solution. A white precipitate of barium sulfate forms. Write the ionic equation, including state symbols, for this reaction.

GCSE Edexcel Chemistry Negative ions- Sulphate test: Excess dilute sulfuric acid is a

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. E... 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.

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Answer

When the gas produced is carbon dioxide (CO₂), it reacts with limewater (a saturated solution of calcium hydroxide) to form calcium carbonate. This reaction is indicated by the limewater turning cloudy, which confirms the presence of carbonate ions (CO₃²⁻) in the copper compound. Therefore, the formation of a cloudy solution of limewater serves as a test for the presence of carbonate anions.

Step 2

Give the name or the formula of the pale blue precipitate.

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Answer

The pale blue precipitate formed when sodium hydroxide is added to the blue solution is copper(II) hydroxide, which has the formula Cu(OH)₂.

Step 3

Write the ionic equation, including state symbols, for this reaction.

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Answer

The ionic equation for the reaction between barium chloride and sulfate ions is:

ext{Ba}^{2+}(aq) + ext{SO}_4^{2-}(aq) ightarrow ext{BaSO}_4(s)

In this equation, barium ions ( ext{Ba}^{2+}) and sulfate ions ( ext{SO}_4^{2-}) are in aqueous solution (aq), and barium sulfate (BaSO₄) is a solid precipitate (s).

Excess dilute sulfuric acid is added to a solid sample of a copper compound - Edexcel - GCSE Chemistry - Question 4 - 2017 - Paper 1

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

Explain how this result is used to identify the anion in the copper compound.

Give the name or the formula of the pale blue precipitate.

Write the ionic equation, including state symbols, for this reaction.

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