An iron nail is left in blue copper sulphate solution. After a while the solution turns pale green and a brown coating forms on the nail. What does this show?

Copper is more reactive than iron and displaces itCorrect answerYour answerIron is more reactive than copper and displaces it from the solutionCorrect answerYour answerThe nail has rusted in the waterCorrect answerYour answerCopper sulphate has changed into iron oxideCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Fe + CuSO₄ → FeSO₄ + Cu.
The brown coating is copper metal, and the pale green colour is iron sulphate. A more reactive metal displaces a less reactive one from its salt.

Worth noting

Rust is reddish-brown too, but rust would not change the solution from blue to green.

Concept: Displacement and the reactivity series
Typical timeTypical: 90 s
Your timeYours: —

The rule this testsMetals and non-metals

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An iron nail is left in blue copper sulphate solution. After a while the solution turns pale green and a brown coating forms on the nail. What does this show?

Explanation