Reactivity Of Metals

MATERIALS REQUIRED

Apparatus: Test tubes, test stand,

Chemical Compounds: Metals-Zn granules, Fe filings, Cu turnings, Al foil and aqueous solutions of zinc sulphate, ferrous sulphate, copper sulphate, and aluminium sulphate.

THEORY

Metals are elements which are good conductors of heat and electricity. Most metals lose electrons in chemical reactions to become electropositive. The alkali metal comprises group 1 of the periodic table.

1. The metals have been arranged in the decreasing order of reactivity in a series. This series is known as the reactivity or activity series.

2. The reactivity series of metals is used for predicting the products of displacement reactions and the reactivity of metals in other reactions. Potassium is the most reactive metal, while platinum is the least reactive.

3. A more reactive metal can displace less reactive metals from its salt solution or compounds If 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.

4. Displacement reactions are prevalent in metals due to the relative strength of metal to displace other metals from their salt solution. In a displacement reaction, a more reactive metal can displace a less reactive metal from its salt solution. The reaction is often known as metal displacement reaction.

When zinc granules are immersed in the copper sulphate solution, the initial colour of copper sulphate from blue starts get changed to colourless with reddish brown particles of pure copper settle at the bottom of the test tube. This chemical change for the following reaction :

Some other displacement reactions using zinc and iron are as follows :

Colour of solutions and metals

PROCEDURE

1. Take four clean, dry test tubes and label them as 'A', 'B'_, 'C' and 'D'.

2. Pour 10 ml of the given aqueous solution into their respective test tubes.

3. Add a small piece of Aluminum foil to each of these test tubes.

4. Observe the changes and record your observations.

5. Repeat the above steps using :

(a) Copper turnings with ZnSO₄, FeSO₄, CuSO_4, and Al₂(SO₄)₃ solutions.

(b) Iron filings with ZnSO₄, FeSO₄, CuSO_4, and Al₂(SO₄)₃ solutions.

(c) Zinc granules with ZnSO₄, FeSO₄, CuSO_4, and Al₂(SO₄)₃ solutions.

6. Record your observations in the following table :

OBSERVATIONS :

1. When aluminium foil (Al) is added to all the 4 test tubes:

2. When copper turnings (Cu) are added to all the 4 test tubes:

3. When iron fillings are added in all the 4 test tubes:

4. When Zinc granules are added in all the 4 test tubes:

RESULT

1. Aluminium can displace Fe, Cu, and Zn from their salt solutions. Therefore Aluminum is most reactive among them.

2. Copper is unable to displace any metal among Al, Fe, and Zn from their salt solutions. Therefore Cu is the least reactive element among them.

3. Iron being less reactive than zinc is unable to displace Zn from its salt solution, whereas Zn can displace Fe from its salt solution. Therefore Zn is more reactive than Fe.

4. The decreasing order of reactivity for metals are as follows :

PRECAUTIONS

1. Handle the chemicals with care.

2. Clean each metal using sandpaper to remove the oxide layer.

3. Observe the changes patiently as few reactions may occur slowly.

4. Never taste the chemicals.

5. Rinse the test tube properly with water before use.

The basic principle involved in this experiment is that displacement reaction taking place due to the reactivity series of metals.

All metals differ in the number of valence electrons and number of valence shell. Due to this, they have different tendency to lose electrons and thus have a difference in reactivities.

Displacement reaction is used to determine relative reactivities of metals.

Displacement Reaction: A single displacement reaction is also called a substitution reaction. In these reactions, a free element displaces another element from its compound, producing a new compound. The basic format of the reaction can be written as:

A + BX → AX + B

Potassium (K) is the most reactive metal, and gold (Au) is the least reactive metal.

Zinc is more reactive than copper. During the reaction of Zinc with Copper sulphate solution, zinc displaces copper from the solution making a blue solution of copper sulphate colorless.
The reaction is below:

Reactivity series of metals indicate that the metals that are high in reactivity series displace metals that are low in reactivity series. This series helps us to know which metal displaces which metal and helps in electrolysis and many more reactions to get the final product.

When an iron nail is dipped in copper sulphate solution, as iron is higher in reactivity series it will displace copper from its salt. This will make the change in color of copper sulphate from blue to pale green. The reaction looks like:

Fe²⁺(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu²⁺(s)

Gold and silver are very less reactive. Due to which they can last longer without being affected by air and moisture and thus retains their luster.

No, we can not store ZnSO₄ solution in Al vessel.

Reason: Al being more reactive than zinc will displace zinc from the solution and the vessel will be distorted.

Reaction Involved:

Al³⁺(s) + Zn²⁺(aq) → Al³⁺(aq) + Zn²⁺(s)

(i) Copper Sulphate - Blue

(ii) Ferrous Sulphate – Pale Green

(iii) Zinc Sulphate – Colourless

(iv) Aluminum Sulphate – Colourless

(i) Zinc – Silvery White (Greyish)

(ii) Iron – Blackish Grey

(iii) Copper – Reddish Brown

(iv) Aluminum – White

The reactivities of metals are:

Hence,

Al > Zn > Fe > Cu

We will use Ferrous Sulphate solution (FeSO₄) and Aluminium foil for comparing the reactivities of zinc and iron.

Reaction:

An ionic compound which contains a cation(+ve) and anion(-ve) other than (H⁺) and (OH^-1) is called a salt. The commonly used salts are:
i. Common Salt - NaCl

ii. Baking Soda – NaHCO₃

Salts are ionic compounds and thus follow single displacement reaction with metals. Due to which a metal can displace other metals from its salt.

Reaction:

A + BX → AX + B

Where A is metal and BX is a salt of B(metal). After the reaction, A displaces B from its salt and AX is formed leaving behind B.

No solution will take place.

Reason: As the less reactive metal could not displace the high reactive metal, no reaction will take place.

Metals may contain some impurities prior to experiment. These impurities can cause hindrance during reaction so to get proper observation metals are cleaned with sandpaper.

i. Cu + Al₂(SO4)₃ ⇒ No change observed
Explanation: Because copper (Cu) is less reactive than aluminium (Al), it cannot displace Al from its salt solution. Hence, no change observed.

ii. Cu + CuSO₄ ⇒ No change observed
Explanation: A metal cannot displace itself from its salt solution. Hence, no change is observed.

iii. Zn + FeSO₄⇒ Because Zn is more reactive than Iron (Fe), hence Zn displaces Fe from its salt solution. The original pale green solution FeSO₄ becomes colourless.

No, copper cannot displace hydrogen from acids and water. This is because, all the metal which lie below the position of “hydrogen” in the reactivity series, are less reactive than hydrogen, hence, these metals cannot displace hydrogen from acids & water.

The complete reaction is Zn + H₂O → Zn(OH)₂ + H₂

Zn is more reactive than hydrogen, as it lies above hydrogen in the reactivity series. Hence, Zn displaces H from water and forms zinc hydroxide i.e. Zn(OH)₂