Solution A contains the compound [Cu(H₂O)₄]Cl₂ - AQA - A-Level Chemistry - Question 7 - 2017 - Paper 1
Question 7
Solution A contains the compound [Cu(H₂O)₄]Cl₂.
1. State the type of bonding between the oxygen and hydrogen in this compound.
2. State why the chloride ions in th... show full transcript
Worked Solution & Example Answer:Solution A contains the compound [Cu(H₂O)₄]Cl₂ - AQA - A-Level Chemistry - Question 7 - 2017 - Paper 1
Step 1
State the type of bonding between the oxygen and hydrogen in this compound.
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Answer
The bonding between the oxygen and hydrogen in the compound [Cu(H₂O)₄]Cl₂ is covalent. This is because the oxygen atom shares its electron with the hydrogen atom, forming a bond without the complete transfer of electrons.
Step 2
State why the chloride ions in this compound are not considered to be ligands.
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Answer
The chloride ions (Cl⁻) in the compound are not considered ligands because they do not donate a lone pair of electrons to the central metal ion (Cu²⁺) to form a coordinate bond. Instead, they are simply anionic spectators.
Step 3
Write an ionic equation for the reaction that occurs when solution A is converted into solution B and state the colour of solution B.
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Colour:
The colour of solution B is deep blue, indicating the formation of the tetraamminecopper(II) complex.
Step 4
Identify the blue-green solid C.
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Answer
The blue-green solid C formed when sodium carbonate is added to solution A is copper(II) carbonate, CuCO₃.
Step 5
Identify reagent D and write an ionic equation for the reaction that occurs when the yellow-green solution is formed from solution A.
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Answer
Identify of reagent D:
Reagent D is hydrochloric acid (HCl).
Equation:
[Cu(H2O)4]2++4Cl−→[CuCl4]2−+4H2O
Step 6
Explain why colorimetry cannot be used to determine the concentration of solutions containing [CuCl₂].
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Answer
Colorimetry cannot be used to determine the concentration of solutions containing [CuCl₂] because the copper(II) ion does not absorb light in visible wavelengths. Consequently, the colorimetry method would not yield accurate measurements as there would be no significant change in light absorption for the quantification.
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