NIOS Class 10 Science and Technology Activity 4.3 Chemical Reactions and Equations

\In this activity, we will explore what happens when ferrous sulphate is heated and what type of chemical reaction takes place.

NIOS Class 10 Science and Technology Project File

This activity is based on the NIOS class 10 science and technology chapter 4, Chemical Reactions and Equations

Aim of the activity

To observe the thermal decomposition of ferrous sulphate

Materials Required

    1. Ferrous Sulphate crystals (2 grams)

    2. Test tube

    3. Holder

    4. Bunsen burner or spirit lamp

    5. Safety gloves and goggles

Procedure

We take 2 g of ferrous sulphate crystals in a hard glass test tube and hold it using a holder. Now we gently heat it over a flame and observe the changes.

Observation

We notice that the green colour of the crystal fades and turns brown. We also observe the release of a strong, unpleasant smell and water vapours on the wall of the test tube.

Explanation

On heating, ferrous sulphate crystals lose water of crystallisation and form anhydrous ferrous sulphate.

FeSO₄.7H₂O →FeSO₄  + 7H₂O

When anhydrous ferrous sulphate is heated continuously, it decomposes into ferric oxide, sulphur trioxide and sulphur dioxide gases.

2FeSO₄   →Fe₂O₃ + SO₃  +SO₂

 Ferric oxide is a brown solid, and SO₃ and SO₂ are pungent-smelling gases.

Conclusion

This activity demonstrates the thermal decomposition reaction.

Frequently Asked Questions

    1. What type of reaction takes place in this activity?

Answer – Thermal decomposition

   2. Why does the green colour fade away?

Answer – The green ferrous sulphate converts into ferric oxide, which is brown in colour.

   3. What causes the pungent smell in this activity?

Answer – The pungent smell is due to the formation of SO₃ and SO₂ gases.

   4. Give another example of a thermal decomposition reaction.

Answer – 2Pb(NO₃)_2(s)  →2PbO_(s) + NO_2(g) +O_2(g)

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