Question

Five 100ml beakers were taken and labelled a, b, c, d,and e about 50 ml of water was taken in each of the beaker and following substances were added to each of them, left undisturbed for sometime and observations where recorded:

Beaker A :CuSo4+Zn

Beaker B :CuSo4+Fe

Beaker C :ZnSo4+Cu

Beaker D :FeSo4+Cu

Beaker E :ZnSo4+Fe

Write also the relevant chemical equation.

Answer 1

In beaker ‘A’ zinc (Zn) replaces copper (Cu) from copper sulphate (CuSO4). That is why the blue colour of copper sulphate disappears and a powdery red mass of copper is deposited at the bottom of the beaker. The reaction can be represented as follows:

Copper Sulphate (CuSO₄) + Zinc (Zn)

. (Blue)

→ Zinc Sulphate (ZnSO₄) + Copper (Cu)

. (Colourless) . (Red)

Beaker B:-
CuSO4 + Fe- FeSO4+ Cu

There could have been displacement of zinc by copper in beaker ‘C’ and by iron in beaker ‘E’. Similarly iron could be displaced by copper in beaker ‘D’.

Since we do not see any change in beaker C, we can infer that copper is not able to replace zinc from zinc sulphate

And the rule here is that zinc is more reactive than copper and iron. A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal. Now you can understand why there are no displacement reactions in beakers D and E also.