Four test tubes A, B, C and D are taken. In test tube A iron nail is d

1.	Four test tubes A, B, C and D are taken. In test tube A iron nail is dipped in copper sulphate solution. In test tube B copper wire is dipped in ferrous sulphate solution. In test tube C zinc metal is dipped in ferrous sulphate solution and in test tube D iron nail is dipped in zinc sulphate solution. The reactivity order has been found to be zn > Fe > Cu. In which test tubes was the colour change observed ?(a) A and C(b) A and B(c) B and C(d) B and D
Answer» Correct answer is (a) A and C A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal. ∵ The reactivity order has been found to be zn > fe > cu Therefore, In test tube A \(\longrightarrow\) Iron can replace Cu metal from CuSO₄ solution. \(\underset{\text{blue color}}{CuSO_4(aq)} + Fe(s)\) \(\longrightarrow\) \(Cu(s) + \underset{\text{pale green}}{FeSO_4(aq)}\) In test tube B - Copper can not replace Fe metal from FeSO₄ solution. There will no reaction between copper metal and FeSO₄ solution. Therefore, no change in colour. In test tube C - Zinc can replace, Fe metal from FeSO₄ solution. \(\underset{\text{Pale green}}{FeSO_4(aq)} + Zn(s)\) \(\longrightarrow\) \(\underset{\text{colorless}}{ZnSO_4(aq)} + Fe(s)\) In test tube D - Iron cannot replace, Zn metal from ZnSO₄ solution. There will no reaction between Iron nail and ZnSO₄ solution. Therefore, no change in colour.

Four test tubes A, B, C and D are taken. In test tube A iron nail is dipped in copper sulphate solution. In test tube B copper wire is dipped in ferrous sulphate solution. In test tube C zinc metal is dipped in ferrous sulphate solution and in test tube D iron nail is dipped in zinc sulphate solution. The reactivity order has been found to be zn > Fe > Cu. In which test tubes was the colour change observed ?(a) A and C(b) A and B(c) B and C(d) B and D

Answer»

Correct answer is (a) A and C

A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal.

∵ The reactivity order has been found to be zn > fe > cu

Therefore,

In test tube A \(\longrightarrow\) Iron can replace Cu metal from CuSO₄ solution.

\(\underset{\text{blue color}}{CuSO_4(aq)} + Fe(s)\) \(\longrightarrow\) \(Cu(s) + \underset{\text{pale green}}{FeSO_4(aq)}\)

In test tube B - Copper can not replace Fe metal from FeSO₄ solution.

There will no reaction between copper metal and FeSO₄ solution.

Therefore, no change in colour.

In test tube C - Zinc can replace, Fe metal from FeSO₄ solution.

\(\underset{\text{Pale green}}{FeSO_4(aq)} + Zn(s)\) \(\longrightarrow\) \(\underset{\text{colorless}}{ZnSO_4(aq)} + Fe(s)\)

In test tube D - Iron cannot replace, Zn metal from ZnSO₄ solution.

There will no reaction between Iron nail and ZnSO₄ solution.

Therefore, no change in colour.