Question

Give reason for the flowing:
Copper cannot displace zinc from its salt solution.

Answer 1

A displacement reaction occurs when a metal is put in a salt solution of another metal that has a lower reactivity. The reactivity of metals decreases from top to bottom in the series.

Complete answer:
Metals are typically solid elements that tend to be lustrous, ductile, malleable, and strong conductors of electricity. Metals are very reactive and tend to lose electrons to become positively charged ions. Metals are therefore referred to as electropositive elements.

The reactivity series is a list of metal elements, ordered for their reactivity, with the most reactive at the top and the least reactive at the bottom. The reactivity of metals is due to the variation in the stability of their electron configurations as atoms and ions. Since they are all metals, they can form positive ions as they react.

In the reactivity series, zinc is more reactive than copper. A more reactive metal can replace a less reactive metal, but a less reactive metal cannot replace a more reactive metal. Thus, copper cannot displace zinc from its salt solution, while zinc can displace copper from its salt solution.

For a reaction involving zinc and copper sulphate solution,

${\rm{Zn + CuS}}{{\rm{O}}_{\rm{4}}} \to {\rm{Cu + ZnS}}{{\rm{O}}_{\rm{4}}}$

The zinc displaces the copper from its compound.

Note: The reactivity series shows how ready the different metals are to interact with other materials to form compounds. The elements at the top are much more ready-to-form compounds than the ones at the bottom. This means that a metal higher up the series will "steal" other elements from a metal lower down, leaving it as an uncombined element.