Question

Give reason: blue colour of copper sulphate solution is destroyed when iron filings are added to it.

Answer 1

the blue colour changes to green as it transfer to the iron nails
the iron nails turn pinkish brown.

Answer 2

Explanation:

The ‘blue colour’ of the “copper sulphate solution” is destroyed while the iron filings have been added to the “copper sulphate solution”, because iron has displaced copper from the copper sulphate solution.

The ‘blue color’ of the copper sulphate solution is because of the presence of copper ions and upon displacement of copper ions, the blue color is destroyed. Iron is more electropositive and so displaces “copper from copper sulphate” solution and forms ferrous sulphate which is green in color. The displaced copper is in its elemental form and hence turns reddish brown in color. This reaction is a displacement and exothermic reaction.

$\mathrm{Fe}+\mathrm{CuSO}_{4} \rightarrow \mathrm{FeSO}_{4}+\mathrm{Cu}$

The elemental copper formed gets deposited on the iron filings.