CBSE Class 10 Physics Different Types of Chemical Eeactions Worksheet Set A

 

Different types of chemical reactions

Experiment No: ……1(a)                                       Date: ………..

Combination reaction

Objectives: To study the Combination reaction of Quick lime (CaO) in water

Requirements: CaO, water, beaker, thermometer, stirrer, etc.

Points to remember:

1. CaO is a white powder

2. It reacts with water to form slaked lime [Ca(OH)₂]

3. This process is called slaking of lime

4. Slaked lime is a suspension of Ca(OH)₂ in water.

5. Clear solution of Ca(OH)₂ in water is known as lime water

6. Slaking of lime is an exothermic reaction releasing a lot of heat energy.

7. CaO(s) + H₂O_(l) Ca(OH)₂(s/aq)

• Procedure:

1. Take about 50 ml of water is a beaker and note its temperature and record as T₁ ⁰ C

2. Add 2 spatula of CaO to it.

3. Stir well

4. Note the temperature again and record the same as T ₂⁰C

5. Compare the temperature. (Which is greater? T₁ or T₂?)

• Observations:

1. Initial temperature: T ₁⁰ C = …………. ⁰ C

2. Final Temperature: T ₂⁰ C = ………… ⁰ C

• Result: Reaction between CaO and water is an example of combination reaction and it is an exothermic combination reaction.

• Preacautions:

1. Water used may boil due to chemical reaction and hence touching the hot beaker with bare hand should be avoided.

2. Use goggles and lab coat

3. Hg thermometer should be handled with care.

• Answer the following questions:

1. What is meant by combination reaction?

2. What is the colour of CaO or quick lime?

3. How do you know that dissolution of CaO in water is exothermic?

4. What are exothermic reactions?

5. Does this reaction belong to REDOX type? (Ans: No. No electron exchange takes place)

 Decomposition reaction       

Experiment No: ……1 (b)                               Date: ………..             

• Objectives: To study the decomposition reaction of FeSO₄

• Requirements: Iron sulphate hepta hydrate (FeSO₄.7H₂O), test tube, spatula, Bunsen burner, etc.

• Points to remember:

1. Ferrous sulphate hepta hydrate crystals are light green (pale green) in colour.

2. On heating iron sulphate undergoes decomposition to form solid iron oxide and sulphur dioxide and sulphur trioxide gases. (2FeSO₄.7H₂O Fe₂O₃ + SO₂ + SO₃ + 14H₂O)

3. The gases formed has smell of burning sulphur

4. Iron sulphide is brown in colour.

5. The sulphur oxide gases produced are acidic and can be tested using moist blue litmus paper.

6. Both SO₂ and SO₃ are soluble in water

7. SO₂ + H₂O H2SO₃ (Sulphurous acid)

8. SO₃ + H₂O H2SO₄ (Sulphuric acid)

9. SO₂ will dissolve in water and can be tested using acidified potassium dichromate solution (Yellow solution turns green)

10. The seven water molecules present in the crystal are known as water of crystallisation.

• Procedure:

1. Take a few crystals of iron sulphate hepta hydrate in a clean dry test tube.

2. Heat the test tube strongly on a Bunsen burner.

3. Introduce a moist blue litmus paper near the mouth of the test tube

• Observations:

1. Green colour of the substance gradually changes to brown

2. The white fuming kind of gas released has smell of burning sulphur

3. Blue litmus paper turns to red.

• Result: Light green iron sulphate undergoes decomposition to form brown iron oxide and acidic SO₂ and SO₃ gases. It also loses its water of crystallisation.

• Precautions:

1. Do not inhale the gases that are released.

2. Avoid your eyes getting exposed to the gases.

3. Wear goggle and lab coat.

• Answer the following questions:

1. What are decomposition reactions?

2. What is the colour of hydrated FeSO₄?

3. What is the colour of the residue formed after the experiment? What is it chemically?

4. The gases emitted are ……….. oxides.

Displacement reaction          

Experiment No: …1 (c)                   Date: ………..                                              

• Objectives: To study the Displacement reaction of iron in copper sulphate   

• Requirements: Iron nails, thread, test tubes, copper sulphate, distilled water, spatula, TT stand, sand paper, etc.

• Points to remember:

1. Colour of pure iron is greyish

2. Colour of pure copper is brownish.

3. Aqueous solution of copper sulphate is blue due to the presence of Cu²⁺ ions and ferrous sulphate is light green due to the presence of Fe²⁺ ions.

4. Fe is more reactive than Cu. Due to their difference in reactivity, copper gets deposited on iron when iron is kept in a solution of copper sulphate and metallic iron dissolves in water to form iron sulphate.

5. Due to the above mentioned reactions, the colour of the solution gradually changes from blue to light green.

6. Fe_(s) + Cu²⁺_(aq) Fe²⁺_(aq) + Cu_(s).

7. This is an example of a single displacement reaction. (Fe²⁺ ions displace Cu²⁺ ions)

• Procedure:

1. Take 10 ml each of copper sulphate solution in two test tubes and keep on a TT stand.

2. Take two iron nails and clean them using a sand paper to remove any rust.

3. Put one iron nail in one of the test tubes.

4. After 15 minutes, take out the iron nail keep it on a filter paper next to the clean iron nail and compare them. Compare also the solutions in both the test tubes.

5. Record your observation in the following table.

Conclusions:

Fe displaces Cu from CuSO₄ and forms FeSO₄ in the solution hence the colour of the solution changes from light blue to pale green. The displaced copper gets deposited on iron nail. It appears as brown coating on iron nail.

1. Iron nail should be clean; otherwise impurity such as rust will cause interference to the expected reaction.

2. During the experiment the test tube should not be disturbed. (The deposit of copper might fall off)

3. More the time taken better will be the result.

Questions:

1. What is meant by displacement reaction? (Ans: A stronger element displaces a weaker element from its compound)

2. Which is more reactive? Copper or iron and why? (Ans: Fe is more reactive as it displaces Cu from its compounds)

3. Name the reaction that takes place, when an iron nail is kept in copper sulphate solution. (Sin gle displacement or REDOX)

4. What happens when (write also the chemical equations involved):

a. Zn strip is kept in copper sulphate solution? (Blue solution becomes colourless and brown deposit of Cu)

b. Copper wire is kept in ferrous sulphate solution? (No visible change as Cu cannot displace Fe)

c. Copper wire is kept in silver nitrate solution? (Black deposit of Ag and colourless solution becomes blue)

d. Copper sulphate solution is stored in iron vessel? (Hole will be formed on Fe vessel as Fe displaces Cu from Copper sulphate. Precious copper sulphate solution will be lost)

5. What is the colour of copper sulphate solution before the experiment? (Blue/Peacock blue)

6. Which out of the following get coated on iron nail? What is its colour?

(Copper oxide, copper sulphate, copper sulphide, copper metal) [Reddish brown copper metal)

7. What is the type of reaction that takes place in this experiment? (Chemical displacement)

 

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