When an iron nail is placed in a blue copper sulphate solution, the blue colour gradually fades because the concentration of which ion decreases?
Answer and explanation
Correct answer: Copper(II) ion
The blue colour of copper sulphate solution is due to copper(II) ions. Since iron is more reactive than copper, it displaces copper(II) ions from the solution to form copper metal: \(\mathrm{Fe + CuSO_4 \rightarrow FeSO_4 + Cu}\). Thus, the concentration of copper(II) ions decreases and the blue colour fades. Iron(II) ions are formed, but they are not the ions whose decrease causes the fading.
Frequently asked questions
What is the correct answer to this question?
Copper(II) ion
Why is this the correct answer?
The blue colour of copper sulphate solution is due to copper(II) ions. Since iron is more reactive than copper, it displaces copper(II) ions from the solution to form copper metal: \(\mathrm{Fe + CuSO_4 \rightarrow FeSO_4 + Cu}\). Thus, the concentration of copper(II) ions decreases and the blue colour fades. Iron(II) ions are formed, but they are not the ions whose decrease causes the fading.
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.
