Observing the action of Zn, Fe, Cu and Al metals on the following salt solutions :
(a) ZnSO4(aq.)
(b) FeSO4(aq.)
(c) CuSO4(aq.)
(d) Al2(SO4)3(aq.)
(ii) Arranging Zn, Fe, Cu and Al (metals) in the decreasing order of reactivity based on the above result.
MATERIALS REQUIRED
Test tubes, test stand, metals-Zn granules, Fe filings, Cu turnings, Al foil and aqueous solutions of zinc sulphate, ferrous sulphate, copper sulphate and aluminium sulphate.
THEORY
In a displacement reaction an ion or an atom in a compound is replaced by an ion or an atom of zinc sulphate element. It may be denoted as
X + YZ → XZ + Y
The displacement reactions are based on the reactivity series, where a more reactive metal displaces a less reactive metal from its salt solution.
For three different metals A, B, C if metal A replaces metal B from its aqueous solution then metal A is more reactive than metal B.
It metal C displaces metal B from its salt solution, but metal A displaces metal C from its salt solution it follows that the increasing order of reactivity is :
B < C < A.
When pieces of Zn are dipped in copper sulphate solution, the blue colour of copper sulphate starts fading and reddish brown particles of copper settle at the bottom. This occurs because of the following reaction :
Some other examples of displacement reactions are as follows :
Colour of solutions and metals
Name |
Formula |
Colour |
Aluminium Iron Copper Zinc Aluminium sulphate Ferrous sulphate Zinc sulphate Copper sulphate |
Al Fe Cu Zn Al2(SO4)3 FeSO4 ZnSO4 CuSO4 |
White Balckish grey Reddish brown Silvery white (greyish) Colourless Pale green Colourless Blue |
PROCEDURE
1. Take four test tubes and label them as ZnSO4, FeSO4 and Al2(SO4)3.
2. Pour equal amount of their aqueous solution into the respective test tubes.
3. Add a small strip of Al foil to each of the test tubes.
4. Observe the change and record your observations.
5. Repeat similar procedure using :
(a) Cu turnings with ZnSO4, FeSO4, CuSO4 and Al2(SO4)3 solutions
(b) Fe filings with ZnSO4, FeSO4, CuSO4 and Al2(SO4)3 solutions
(c) Zn granules with ZnSO4, FeSO4, CuSO4 and Al2(SO4)3 solutions
Record your observations in the following table :
OBSERVATIONS
S. No. |
Metal |
Salt solution In which added |
Observation |
Inference |
1. |
Al |
Al2(SO4)3 |
No change observed |
Metal cannot displace itself from its salt solution. |
Al |
FeSO4 |
Pale green colour of the solution disappears and it becomes colourless. Deposits on Al metal are seen. |
Al displaces iron from the salt solution. Therefore, Al is more reactive than Fe. |
|
Al |
ZnSO4 |
No change in colour of the solution, but a new coating is een on Al. |
Al displaces Zn from the salt solution, therefore Al is more reactive than Zn. |
|
Al |
CuSO4 |
Blue colour of the solution disappears and it becomes colourless. Reddish brown deposits are seen on Al. |
Al displaces Cu from the salt solution, therefore Al is more reactive than Cu. |
|
2. |
Fe |
Al2(SO4)3 |
No change observed Fe(s) + Al2(SO4)3(aq) → No Reaction. |
Fe cannot displace Al from the salt solution, therefore, Fe is less reactive than Al. |
Fe |
FeSO4 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
Fe |
ZnSO4 |
No change observed Fe(s) + ZnSO4(aq) → No Reaction |
Fe cannot displace Zn from the salt solution, therefore, Fe is less reactive than Zn. |
|
Fe |
CuSO4 |
Blue solution changes to pale green, reddish brown Cu gets deposited on Fe filings. |
Fe displaces Cu from the salt solution, therefore, Fe is more reactive than Cu. |
|
3. |
Cu |
Al2(SO4)3 |
No change observed Cu(s) + Al2(SO4)3(aq) →No Reaction |
Cu cannot displace Al from salt solution, therefore, Cu is less reactive than Al. |
Cu |
FeSO4 |
No change observed Cu(s) + FeSO4(aq) → No Reaction |
Cu cannot displace Fe from salt solution, therefore, Cu is less reactive than Fe. |
|
Cu |
ZnSO4 |
No change observed Cu(s) + ZnSO4(aq) → No Reaction |
Cu cannot displace Zn from salt solution, therefore, Cu is less reactive than Zn. |
|
Cu |
CuSO4 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
4. |
Zn |
Al2(SO4)3 |
No change observed Zn(s) + Al2(SO4)3(aq) → No Reaction |
Zn cannot displace Al from salt solution, therefore, Zn is less reactive than Al. |
Zn |
FeSO4 |
Pale green solution becomes colourless, Fe gets deposited on Zn granules. |
Zn displace Fe from salt solution, therefore, Zn is more reactive than Fe. |
|
Zn |
ZnSO4 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
Zn |
CuSO4 |
Blue solution becomes colourless, reddish brown Cu gets deposited on Zn granules. |
Zn displace Cu from the salt solution, therefore, Zn is more reactive than Cu. |
RESULT
1. Al is able to displace Fe, Cu and Zn from their salt solutions, therefore Al is most reactive.
2. Cu is unable to displace any metal among Al, Fe and Zn from their salt solutions, therefore Cu is least reactive.
3. Fe is unable to displace Zn from its salt solution, whereas Zn is able to displace Fe from its salt solution, therefore Zn is more reactive than Fe.
4. The decreasing order of reactivity for these metals follow the order :
Al > Zn > Fe > Cu.
PRECAUTIONS
1. Handle the chemicals carefully.
2. Clean each metal with sand paper.
3. Observe the changes carefully as few reactions may occur slowly.
4. Do not taste the chemicals.
5. Wash your hands properly after the experiment.
|
S. No. |
Metal |
Salt solution In which added |
Observation |
Inference |
|
1. |
Al |
Al2(SO4)3 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
Al |
FeSO4 |
Pale green colour of the solution disappears and it becomes colourless. Deposits on Al metal are seen. 2Al(s) + 3FeSO(aq) → Al(SO) + Fe(s) |
Al displaces iron from the salt solution. Therefore, Al is more reactive than Fe. |
|
|
Al |
ZnSO4 |
No change in colour of the solution, but a new coating is een on Al. |
Al displaces Zn from the salt solution, therefore Al is more reactive than Zn. |
|
|
Al |
CuSO4 |
Blue colour of the solution disappears and it becomes colourless. Reddish brown deposits are seen on Al. |
Al displaces Cu from the salt solution, therefore Al is more reactive than Cu. |
|
|
2. |
Fe |
Al2(SO4)3 |
No change observed Fe(s) + Al2(SO4)3(aq) → No Reaction. |
Fe cannot displace Al from the salt solution, therefore, Fe is less reactive than Al. |
|
Fe |
FeSO4 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
|
Fe |
ZnSO4 |
No change observed Fe(s) + ZnSO4(aq) → No Reaction |
Fe cannot displace Zn from the salt solution, therefore, Fe is less reactive than Zn. |
|
|
Fe |
CuSO4 |
Blue solution changes to pale green, reddish brown Cu gets deposited on Fe filings. |
Fe displaces Cu from the salt solution, therefore, Fe is more reactive than Cu. |
|
|
3. |
Cu |
Al2(SO4)3 |
No change observed Cu(s) + Al2(SO4)3(aq) →No Reaction |
Cu cannot displace Al from salt solution, therefore, Cu is less reactive than Al. |
|
Cu |
FeSO4 |
No change observed Cu(s) + FeSO4(aq) → No Reaction |
Cu cannot displace Fe from salt solution, therefore, Cu is less reactive than Fe. |
|
|
Cu |
ZnSO4 |
No change observed Cu(s) + ZnSO4(aq) → No Reaction |
Cu cannot displace Zn from salt solution, therefore, Cu is less reactive than Zn. |
|
|
Cu |
CuSO4 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
|
4. |
Zn |
Al2(SO4)3 |
No change observed Zn(s) + Al2(SO4)3(aq) → No Reaction |
Zn cannot displace Al from salt solution, therefore, Zn is less reactive than Al. |
|
Zn |
FeSO4 |
Pale green solution becomes colourless, Fe gets deposited on Zn granules. |
Zn displace Fe from salt solution, therefore, Zn is more reactive than Fe. |
|
|
Zn |
ZnSO4 |
No change observed |
Metal cannot displace itself from its salt solution. |
|
|
Zn |
CuSO4 |
Blue solution becomes colourless, reddish brown Cu gets deposited on Zn granules. |
Zn displace Cu from the salt solution, therefore, Zn is more reactive than Cu. |
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