Types Of Chemical Reactions

MATERIALS REQUIRED

Apparatus: Test tubes, test tube holder, bunsen burner, tripod stand.

Chemical Compound: Ferrous sulphate crystals, blue litmus paper.

THEORY

1. The crystals of ferrous sulphate are green in colour, due to the presence of water of crystallisation.

2. When these crystals are heated, the colour of the crystal changes from light green to brown colour

3. The following reaction takes place

In this reaction, a single reactant breaks down to give simple products. Therefore, this is a decomposition reaction.

4. The ferrous sulphate on heating decomposes to ferric oxide (Fe₂O₃), sulphur dioxide (SO₂) and sulphur trioxide (SO₃). Ferric oxide is solid while SO₂ and SO₃ are gases.

5. SO₂ and SO₃ turn the moist blue litmus paper red since these gases are acidic in nature.

6. Sulphur dioxide evolved during the reaction can be used to reduce an acidified solution of potassium dichromate. This reaction can be utilized to confirm the presence of sulphur dioxide.

PROCEDURE

1. Take about 2 g crystals of ferrous sulphate in a dry test tube and note the colour of crystals.

2. Using the bunsen burner, heat the test tube containing ferrous sulphate.

3. Bring a moist blue litmus paper in contact with the evolved gases from the test tube.

4. Soak a strip of filter paper in an acidified solution of potassium dichromate and place it above the mouth of the test tube.
5. Note the observation in the observation table.

OBSERVATION TABLE

The experimental procedure is described in the table:

RESULT

On heating, ferrous sulphate crystals, they decompose to give ferric oxide, sulphur dioxide, and sulphur trioxide. Hence, it is a decomposition reaction.

PRECAUTIONS

1. Use heating test tube for heating ferrous sulphate.

2. Always use the test-tube holder for holding the test tube during heating.

3. The gases SO₂ and SO₃ are very harmful, so do not take a deep breath of these gases.

A chemical reaction is a chemical transformation or change in which two or more compounds combine to one or more different substance called the products.

The reactivity of metals depends upon the tendency to lose electrons. The more the tendency of a metal to lose an electron, the more will be its reactivity.

The reactivity of non – metal depends upon tendency to gain an electron. The more the tendency to gain an electron, the more reactive is the non-metal.

In Double displacement reaction, ion of two compound switch there places to form two new compounds.

NaCl(aq)+ AgNO₃→NaNO₃ (aq)+AgCL(s)

In single displacement reaction in which more reactive element takes up the place of another element in a compound.

Zn (s)+CuSO₄ (aq) →ZnSO₄ (aq)+ Cu(s)

The decomposition reaction is that reaction in which a single reactant breaks down to give simple products.

2 FeSO₄ (s) → Fe₂ O₃+ SO₂ (g)+ SO₃ (g)

The ferric oxide is solid while SO₂ and SO₃ are gases. These gases are acidic hence will turn blue litmus red thus have a pH < 7 in ph scale.

The ferrous sulphate (FeSO₄.7H₂O) consists of 7 molecules of water. During crystal formation, this water molecule is called as water the of crystallization, the color of the crystal is due to this water molecule in crystal form. When we heat the crystal this, water et evaporated out from the crystal structure, thus changing the color of the crystal.

The iron ions (Fe²⁺) being at a higher order in reactivity series displaces the copper ions (Cu²⁺), and a new compound Ferrous sulphate is formed.

Fe(s) + CuSO₄ (aq) → FeSO₄ (aq) + Cu(s)

The iron nail being reactive get oxidized due to the oxygen present in the air to form a protective layer of ferric oxide. This protective layer is necessary to be removed to make fresh iron to easily converted in ion when kept in the solution, and This process also increases the speed of the reaction.

No change is observed because Ag being less reactive than Cu is unable to displace it from its solution.

A white precipitate of PbCL₂ will be obtained.

The chemical reaction is given below:
CH₃(COO) �₂Pb (aq) + 2HCl (aq) → 2CH₃COOH (aq) + PbCl₂ (s)

Calcium carbonate get decomposed to calcium oxide and carbon dioxide gas.

Na₂ CO₃+2 HCL(aq) →2 NaCL(s)+H₂ O(aq)+CO₂

The combustion of hydrogen is a combination reaction:

2 H₂ (g)+O₂ (g)→2H₂ O(l)

In Burning of Mg ribbionTwo element combine to form a more complex compound, therefore, the reaction is called as combination reaction.

2 Mg+O₂→2 MgO

In Heating of ferrous sulphate crystal single compounds break down into simpler compounds, so it is a decomposition reaction.

2 FeSO₄ (s)→Fe₂ O₃ (s)+SO₂(g)+SO₃ (g

when barium chloride and sodium sulphate led to the formation of white precipitate due to the formation of BaSO₄.

1.Green/ Pale green : FeSO₄

2. Blue: CuSO₄

3. White crystalline solid: Na₂SO₄ and BaCl₂

Calcium oxide when dissolved in water forms Calcium hydroxide. The reaction is given below:

CaO + H₂O ⇒ Ca(OH)₂

Displacement reactions occur due to the difference between the chemical reactivities of elements. A more reactive element displaces a less reactive element from its salt solution.

i. The chemical reactions that absorb heat are called as endothermic reactions.
Example:
Photosynthesis is an endothermic reaction as plants absorb sun light energy to prepare their food.

ii. The chemical reactions that release heat are called as exothermic reactions.

Example:
Combustion is an exothermic reaction as lot of heat energy is released.

The chemical formula for quicklime is CaO. The chemical name is calcium oxide.

The reactivity series of metal is given below:

MATERIALS REQUIRED

Calcium oxide, water, beaker, glass rod, dropper, red litmus paper, test tube, filter paper, funnel.

THEORY

1. Quick lime is (CaO). It is a white, caustic, alkaline, crystalline solid at room temperature.

Quicklime reacts with water to form calcium hydroxide. As in this reaction two substances – quicklime and water combine to form a new substance. Therefore, this reaction is called a combination reaction. This chemical change can be represented by the given chemical
equation :

During this chemical change, heat is also released. Therefore, this is an exothermic reaction.

PROCEDURE

1. Take some calcium oxide (quicklime) in the beaker and pour some water over quicklime slowly.
2. Stir the solution well with a clean glass rod and touch the outer surface of the beaker.

3. Take a clean dropper and put a drop of liquid solution a red litmus paper.

4. Filter the mixture of the beaker and take about 5 ml of filtrate in a test tube and blow air through the liquid.

OBSERVATION TABLE

The experimental procedure is described in the table :

RESULT

When quicklime and water combine to form calcium hydroxide and heat is released. Therefore this is an exothermic combination reaction.

PRECAUTIONS

1. Quicklime can cause severe burns. Therefore, it should be handled with a spatula.

2. Since the reaction is exothermic, water should be poured over quicklime slowly.

3. The filtrate collected should be removed.

MATERIALS REQUIRED

Apparatus: Test tubes, test tube stand, sandpaper, iron nails, and thread.

Chemical compound: Copper sulphate solution

THEORY

1. On immersion iron nail inside the copper sulphate solution, iron being more reactive displaces the copper from its salt solution.

2. The initial colour of the copper sulphate solution changes from blue which after adding iron nail changes to light green.

3. Iron (Fe²⁺) ions replace the copper ions (Cu²⁺) from the solution and form iron sulphate. Hence it is called a Displacement reaction.

The chemical reaction for the above chemical change is given as follow:

PROCEDURE

1. Take two iron nails and remove the iron oxide layer using sandpaper formed due to oxidation of iron with oxygen in the air.

2. Take two clean, dry test tubes and mark them as ‘A’ and ‘B’ using a marker.

3. In each test tube pour 10 ml of freshly prepared copper sulphate solution.

4. Tie one iron nail using a thread and immerse it in the copper sulphate solution in test tube A in the rest state for 30 minutes and keep aside the second nail to measure the change in the first iron nail.

5. After 30 minutes elapsed, take out the immersed iron nail from the copper sulphate solution and compare the colour of copper sulphate solutions in the test tubes ‘A’ and ‘B’ Also compare the colour of iron nail with one kept aside for testing purpose.

OBSERVATIONS

The primary colour of copper sulphate solution is blue which after immersing iron nails get changed to light green.

After immersing nail into copper sulphate solution, a brown coat develops over the surface of the iron nail. Because of this coat of copper oxide on the surface of iron nail clour get changed to brown colour.

RESULT

On Immersing the iron nails into the copper sulphate solution, displacement reaction takes place.

Iron being more reactive than copper displaces the copper ions from its salt solution, and two new products ferrous sulphate and the pure copper in solid is formed as the product of the given chemical reaction.

PRECAUTIONS

1. The iron nails should be cleaned using sandpaper.

2. The iron nail must be completely immersed in the copper sulphate solution.

3. Do not touch copper sulphate or the iron nail dipped in that solution as it can disturb the reaction.

MATERIALS REQUIRED

Apparatus: Test tubes, beaker.

Chemical compound: Sodium sulphate solution, barium chloride solution

THEORY

1. Sodium sulphate and barium chloride being initially colourless.
2. On mixing two solutions, a white coloured compound barium sulphate is found.
3. Barium sulphate being insoluble in water get precipitated on the surface of the solution

4. In this reaction, both the reactants, i.e., sodium sulfate and barium chloride exchange ions. Hence, this type of exchange of ion called as a double displacement reaction.

The chemical reaction can be given as follow :

PROCEDURE

1. Take 10 ml of sodium sulphate and barium chloride solution in a clean, dry test tube and mark it as ‘A' and ‘B.’

2. Empty the solutions of test tubes ‘A’ and ‘B’ inside a beaker.

3. With the help of a glass rod, stir the mixture kept in a beaker.

4. Record your observation.

OBSERVATIONS

The reaction of sodium sulphate with barium chloride gives a white precipitate of barium sulphate, and sodium chloride is formed as a product of the reaction.

RESULT

On intermixing the solutions of sodium sulphate and barium chloride, a double displacement, reaction occur. In this reaction sodium sulphate reacts with barium chloride to form new products, barium sulphate (white ppt) and sodium chloride are formed.

PRECAUTIONS

1. Clean the apparatus properly before using them.

2. Test tubes, beaker and glass rod should be rinsed properly before use.

3. An equal amount of sodium sulphate and barium chloride solutions should be used.