To perform Action of heat on ferrous sulphate crystals and classify it - Lab Work

To perform Action of heat on ferrous sulphate crystals and classify it on Combination reaction, Decomposition reaction, Displacement reaction and Double displacement reaction

Aim

 To perform Action of heat on ferrous sulphate crystals and classify it on:
i. Combination reaction
ii. Decomposition reaction
iii. Displacement reaction
iv. Double displacement reaction

Theory
(a) Ferrous sulphate is a crystalline solid (FeSO₄.7H₂O).
(b) When heated strongly it looses the water of crystallization and then decomposes. The reactions are as following
Reaction:   FeSO₄.7H₂O(s)   →(heat)   FeSO₄(s) + 7H₂O
                 2FeSO₄(s)      →(heat)           Fe₂O₃(s)      +  SO₂(g) + SO₃(g)
Ferrous Sulphate(Light green)      Ferric oxide(Brown)
(c) Here, Ferrous Sulphate gives three products on heating. thus, it is a decomposition reaction.

Chemicals Required
Ferrous sulphate crystals and Blue litmus paper.

Apparatus Required
Test tube holder, Test tubes, Boiling tube and Burner

Procedure

Step 1: About 5 g ferrous sulphate crystals in a dry boiling tube is taken.
Step 2: The colour of the ferrous sulphate crystals is noted.
Step 3: The boiling tube is heated.
Step 4: The colour of the crystals after heating is observed.
Step 5: A gas is evolved which is smelled.
Step 6: A wet blue litmus paper is brought near the mouth of the boiling tube.

Observation
1. When ferrous sulphate crystals are heated their colour changes.
2. A gas with smell of burning sulphur is evolved.
3. The gas turns wet blue litmus paper to red.

Inference
1.When heated, ferrous sulphate crystals are decomposed to produce Ferric oxide, sulphur dioxide and sulphur trioxide.
2. Such reactions are called decomposition reaction.

Precautions
1. Use hard glass test tube as boiling tube.
2. Keep the mouth of the boiling tube away from you.

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