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AimObserve and classify the following chemical reactions as one of the four types: combination reaction, decomposition reaction, displacement reaction, or double displacement reaction:
(i) The reaction of water with quicklime
(ii) The reaction of heat with ferrous sulphate crystals
(iii) Iron nails immersed in copper sulphate solution
(iv) The reaction between sodium sulphate and barium chloride solution.
Theory(i) Action of water on quicklime: This is a combination reaction as quicklime (CaO) combines with water to form calcium hydroxide [Ca(OH)2].
CaO(s) + H2O(l) → Ca(OH)2(aq)
(ii) Action of heat on ferrous sulphate crystals: This is a decomposition reaction as ferrous sulphate crystals [FeSO4.7H2O] break down upon heating to form ferric oxide (Fe2O3), sulfur dioxide (SO2), sulfur trioxide (SO3), and water vapor (H2O).
FeSO4.7H2O(s) + heat → Fe2O3(s) + SO2(g) + SO3(g) + 7H2O(g)
(iii) Iron nails kept in copper sulphate solution: This is a displacement reaction as the iron (Fe) in the iron nails displaces copper (Cu) from the copper sulphate solution, forming iron sulfate (FeSO4) and copper metal (Cu).
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
(iv) Reaction between sodium sulphate and barium chloride solutions: This is a double displacement reaction as the sodium (Na+) and barium (Ba2+) ions in the respective compounds exchange to form sodium chloride (NaCl) and barium sulfate (BaSO4).
Na2SO4(aq) + BaCl2(aq) → 2NaCl(aq) + BaSO4(s)


(i) Action of water on quicklimeMaterials needed:
1 .Quicklime(calcium oxide)
2 .Water
3 .Beaker or flask		Procedure:
Take a small amount of quicklime and put it in a beaker or flask.
Slowly add water to the beaker or flask.
Observe the reaction.		Observation: The reaction is highly exothermic and produces a lot of heat. The quicklime reacts with water to produce slaked lime (calcium hydroxide) in a combination reaction.
Equation: CaO + H2O → Ca(OH)2
Classification: Combination reaction
(ii) Action of heat on ferrous sulphate crystalsMaterials needed:
1 .Ferrous sulphate crystals
2 .Test tube or crucible
3 .Bunsen burner		Procedure:
Take some ferrous sulphate crystals in a test tube or crucible.
Heat the test tube or crucible using a Bunsen burner.
Observe the reaction.		Observation: On heating, the ferrous sulphate crystals lose their water of crystallization and turn white. This is a decomposition reaction.
Equation: FeSO4.7H2O → FeSO4 + 7H2O
Classification: Decomposition reaction
(iii) Iron nails kept in copper sulphate solutionMaterials needed:
1 .Iron nails
2 .Copper sulphate solution
3 .Beaker or flask		Take a beaker or flask and pour some copper sulphate solution in it.
Add some iron nails to the solution.
Observe the reaction.
Observation: After some time, the iron nails lose their shine and the blue color of the copper sulphate solution fades. This is because the iron displaces the copper from copper sulphate to form iron sulphate, which is pale green in color.
Equation: Fe + CuSO4 → FeSO4 + Cu
Classification: Displacement reaction
(iv) Reaction between sodium sulphate and barium chloride solutionsMaterials needed:
1 .Sodium sulphate solution
2 .Barium chloride solution
3 .Test tube or flask		Procedure:
Take equal amounts of sodium sulphate and barium chloride solutions in a test tube or flask.
Observe the reaction.		Observation: When sodium sulphate and barium chloride solutions are mixed, a white precipitate of barium sulphate is formed. This is a double displacement reaction.
Equation: Na2SO4 + BaCl2 → 2NaCl + BaSO4
Classification: Double displacement reaction