Metals and salt solutions
The last test is what happens when a metal is put into a salt solution of another metal.
Activity 16.7
- Add aqueous copper sulphate (CuSO4) solution to a beaker.
- Add a strip of zinc (Zn) to it.
- Record your observations.
The observation
Copper sulphate solution is blue. When the zinc strip is added, it can be observed that the intensity of the blue gradually fades and a brown powder forms.
What takes place is a single displacement reaction — the zinc displaces the copper.
Zn + CuSO4 → ZnSO4 + Cu
Now try it the other way round
Copper into zinc sulphate solution
ZnSO4 + Cu → no change
When copper (Cu) is added to a zinc sulphate (ZnSO4) solution, no reaction takes place.
This works in one direction only
Zinc can displace copper, but copper cannot displace zinc. So zinc is the more reactive of the two.
This single pair of experiments settles the order of two metals — and that is the principle of the next page.