RBSE Class 10 Science Chapter 1 Activity 1.5 Solution- Chemical Reactions and Equations

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Activity 1.5 helps students understand the effect of heat on ferrous sulphate crystals. When ferrous sulphate crystals are heated, the colour of crystals changes. This activity demonstrates both thermal decomposition and the concept of water of crystallization which are important topics.

RBSE Class 10 Science Chapter 1 Activity 1.5 Solution-

 

Activity 1.5 Class10 Science

 

Objective

To observe the effect of heat on ferrous sulphate crystals and identify the changes in the colour due to the chemical reaction.

Material Required

  1. Boiling tube
  2. Ferrous sulphate crystals
  3. Tongues
  4. Spirit lamp or burner

Procedure

RBSE Class 10 Science Chapter 1 Activity 1.5 Solution- Chemical Reactions and Equations

 

  • Take about 2g of ferrous sulphate crystals in a dry boiling tube.
  • Hold the boiling tube with the help of tongs.
  • Heat the boiling over the flame of a spirit lamp or burner.
  • Observe the colour changes and any gases evolved during heating.

Observation

  •  Initially ferrous sulphate crystals are light green in colour.
  • On heating the crystals lose their green colour and become white.
  • On further heating, the residue turns brown.
  • A pungent smell is produced due to the evolution of Sulphur dioxide and Sulphur trioxide gases.

 

Chemical Reactions

 

FeSO4.7H2O(s)    →   FeSO4(s) + 7H2O(g)

2FeSO4(s)     →   Fe2O3(s) +     SO2(g)    +SO3(g)

Explanation

Ferrous sulphate crystals are hydrated salts containing water of crystallization which is responsible for green colour of crystals.

When ferrous sulphate crystals are heated, they lose water of crystallization and become anhydrous ferrous sulphate which is white in colour

On further heating of anhydrous ferrous sulphate produces ferric oxide, Sulphur dioxide and Sulphur trioxide.

 

Type of Chemical Reaction

Thermal Decomposition Reaction

A reaction in which a compound breaks down into simpler substances on heating is called a thermal decomposition reaction.

 

Conclusion

The activity shows the loss of water of crystallization and decomposition reaction of ferrous sulphate that produces ferric oxide (dark brown), SO2 and SO3 gases with pungent smell.

 

Precautions

  • Do not point the mouth of the boiling tube towards yourself or others.
  • Use tongs while heating the boiling tube.
  • Perform the activity under the supervision of a teacher.
  • Avoid inhaling the gases evolved during the reaction.
  • Handle hot apparatus carefully.

 

Viva Questions and Answers

 

Q1. What is the colour of ferrous crystals?

Answer

 Light green

Q2. Why are ferrous sulphate crystals green in colour?

Answer

 The green colour is due the presence of water of crystallization.

Q3. What happens when ferrous sulphate crystals are heated?

Answer

They lose water of crystallization and later decompose into ferric oxide, sulphur dioxide and sulphur trioxide.

Q4. What is the colour of anhydrous ferrous sulphate?

Answer

White

Q5. What is the colour of ferric oxide?

Answer

 Brown or reddish brown

Q6. which gases are evolved during decomposition?

Answer

Sulphur dioxide and Sulphur trioxide

Q7. What type of reaction is demonstrated in this activity?

Answer

 Thermal decomposition reaction

Q8. What is water of crystallization?

Answer

Water molecules chemically bound within a crystal structure.

 

Key Learning Points

  •  Ferrous sulphate crystals contain water of crystallization.
  • On heating, they lose water and become white.
  • Further heating causes decomposition of ferrous sulphate.
  • Ferric oxide Sulphur dioxide and Sulphur trioxide are formed.
  • The reaction is a thermal decomposition.
  • Sulphur dioxide and Sulphur trioxide produce a pungent smell.

 

Multiple Choice Question

  1. What is the colour of ferrous sulphate crystals?
  1. Yellow
  2. Red
  3. Light Green
  4. White

Correct answer – c)  Light Green

2.How many water molecules are present in one molecule of ferrous sulphate?

  1. 5 molecules
  2. 7 molecules
  3. 8 molecules
  4. 2 molecules

Correct answer- b)  7 molecules

3.SO2 gas evolves during decomposition of ferrous sulphate, which another gas evolves?

  1. SO4
  2. SO3
  3. CO2
  4. None of the above

Correct answer – b)  SO3

4.Name the chemical reaction involve in the heating ferrous sulphate.

  1. Decomposition reaction
  2. Combination reaction
  3. Displacement reaction
  4. None of the above

Correct answer- a) Decomposition reaction

5.Name the substance remains in the test tube as residue.

  1. Ferric oxide
  2. Ferrous oxide
  3. Ferrous sulphite
  4. Ferrous sulphide

Correct answer – a)   Ferric oxide

6.Why are ferrous sulphate crystals green in colour?

  1. Due to ferric oxide
  2. Due to water of crystallization
  3. Due to sulphur dioxide
  4. Due to heat

Correct answer – b).   Due to water of crystallization

7.What is formed when ferrous sulphate crystals lose water of crystallization?

  1. Ferric oxide
  2. Sulphur dioxide
  3. Anhydrous ferrous sulphate
  4. Sulphur dioxide

Correct answer – c.  Anhydrous ferrous sulphate

8.Name the brown-coloured substance is formed on further heating?

  1. Zinc oxide
  2. Ferric oxide
  3. Copper oxide
  4. Magnesium oxide

Correct answer – b.   Ferric oxide

9.What causes the pungent smell during the reaction?

  1. Water vapour
  2. Ferric oxide
  3. SO2 and SO3
  4. Oxygen

Correct answer – c.  SO2 and SO3

Related Topics 

RBSE Class 10 Science Activities Solution