Fading of the blue colour of copper sulphate is related to which ionic change?
Answer and explanation
Correct answer: Number of copper ions decreases
The blue colour of copper sulphate solution is mainly associated with hydrated Cu²⁺ ions. When an iron nail is placed in the solution, iron displaces copper: Fe + Cu²⁺ → Fe²⁺ + Cu. Copper ions are removed from the solution and deposited as copper metal, while the pale-green Fe²⁺ solution forms. Consequently, the blue colour fades because the number of Cu²⁺ ions decreases, so A is correct.
Frequently asked questions
What is the correct answer to this question?
Number of copper ions decreases
Why is this the correct answer?
The blue colour of copper sulphate solution is mainly associated with hydrated Cu²⁺ ions. When an iron nail is placed in the solution, iron displaces copper: Fe + Cu²⁺ → Fe²⁺ + Cu. Copper ions are removed from the solution and deposited as copper metal, while the pale-green Fe²⁺ solution forms. Consequently, the blue colour fades because the number of Cu²⁺ ions decreases, so A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
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