Classification of the chemical reactions as(i) combination (ii) decomposition (iii) displacement(iv) double displacement reaction

Classification of the chemical reactions as(i) combination (ii) decomposition (iii) displacement(iv) double displacement reaction

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Standard 10th Science Experiment 3 Answer Solutions: Classification of the chemical reactions as(i) combination (ii) decomposition (iii) displacement(iv) double displacement reaction Answers and Solutions.

Aim : 

To classify the given chemical reactions into the type (i) combination (ii) decomposition (iii) displacementand (iv) double displacement. (A) Action of water on quick lime (CaO).(B) Effect of heat on ferrous sulphate crystals.(C) Reaction of copper sulphate solution with iron nails.(D) Reaction between sodium sulphate and barium chloride solutions.

Requirements : 

250 ml beaker, china dish, asbestos sheet, dropper, hard glass test tubes, test tube holder,test tube stand, sandpaper, filter paper, burner/spirit lamp.

Chemicals : 

Quick lime, ferrous sulphate crystals, iron nails, copper sulphate solution, sodium sulphatesolution, barium chloride solution, water

(A) Action of water on quick limeProcedure :

  1. Take about 10 g of quick lime (CaO) in a clean chinadish. Place the china dish on an asbestos sheet.
  2. Take some water in a beaker. With the help of a dropperadd a few drops of water on quick lime in the dish.Record your observations.

Inferences :

(1) The reaction between quick lime and water is

exothermic

 reaction. (2) Here calcium oxide and water react to form

calcium hydroxide (slaked lime).

 (3) This is an example of

combination reaction.

 (4) The clear solution obtained after the suspension settles is called

lime water.

Precautions :

(1) Never put quick lime in water. It may cause the lime water splash out of the beaker and damage eyesor skin.(2) Do not touch or dip your finger in lime water.

(B) Effect of heat on ferrous sulphate crystalsProcedure :

  1. Take about 10 g of ferrous sulphatecrystals in a clean and dry hard glass test tube. Observe the colourof the crystals.
  2. Hold the test tube with a test tubeholder. Heat the test tube gently onlow flame of a burner for about 10minutes.
  3. Note the smell and colour of the gasevolved. 
  4. Continue heating till the colour ofthe residue in the test tube changes. 
  5. Place the hot test tube on asbestossheet. Observe the colour of theresidue after cooling

Inferences :

  1. Light green crystals of ferrous sulphate on heating undergo decomposition. A mixture of SO3 and SO2 gases formed. 
  2. A residue of red colour remains in the test tube. 
  3. This is an example of decomposition reaction.

Precautions :

  1. Use hard glass test tube for heating the substance. 
  2. During heating, keep the test tube away from you.

(C) Reaction of copper sulphate solution on iron nailsProcedure :

  1. Take about 20 ml of copper sulphate solution in a test tube. Note its colour. 
  2. Take 2 or 3 iron nails free from rust. Clean them with sandpaper and wash with water. Note the colourof the iron nails.
  3. Place the iron nails in copper sulphate solution for about 15 minutes.
  4. Remove the nails from the solution, wash them with water and keep them on a filter paper to dry.
  5. Finally note the colour of the solution as well as the nails after reaction.

Chemical reaction :

Fe(s) Iron(steel Grey)Copper sulphate(sky blue)Ferrous sulphate(light Green) CuSO4 (aq)Cu(s)FeSO4 (aq)++

Inferences :

  1. On immersing the brown coloured iron nails in blue coloured copper sulphate solution, they displace copper from the copper sulphate solution and their colour becomes reddish
  2. This is a displacement reaction.

Precaution :

Clean the iron nails by rubbing with sandpaper for effective result.

(D) Reaction between sodium sulphate solution and barium chloride solutionProcedure :

Diagram :

Reaction between sodium sulphate solution andbarium chloride solution

  1.  Take about 15 ml of sodium sulphate solution in aclean beaker. Note its colour and appearance.
  2. Take about 5 to 10 ml of barium chloride solution in aclean test tube. Note its colour and appearance.
  3. Add barium chloride solution to sodium sulphatesolution with constant stirring. Observe the changesand note them.

Multiple Choice Questions

Choose the correct alternative and write its letter (A), (B), (C), (D) in the box :

 To observe the reaction of water on quick lime, .

 A) quick lime is added to water in a test tube (B) a lot of water is added to quick lime (C) a few drops of water are added to quick lime (D) none of these

Answer: C

2. When crystals of Ferrous sulphate are strongly heated, the residue obtained is . 

(A) red in colour (B) blue in colour (C) green in colour (D) colourless

Answer: A

3. When Barium chloride solution is added to Sodium sulphate solution, .

(A) blue precipitate is formed (B) white precipitate is formed (C) green precipitate is formed (D) no reaction takes place

Answer: B

4. The reaction of iron nails with copper sulphate solution is an example of .

 (A) combination reaction (B) decomposition reaction (C) displacement reaction (D) double displacement reaction

Answer: C

5. Reddish brown deposit formed on iron nails kept in a solution of copper sulphate is .

 (A) Cu2O (B) Cu (C) CuO (D) CuS

Answer: B

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