CLASS 10
CHEMISTRY EXPERIMENTS-1 and 2
draw diagrams on the white page

Experiment 1. Performing and observing the following reactions and classifying them into :

a) Combination reaction     -(i) Action of water on quick lime

b) Decomposition reaction    -ii) Action of heat on ferrous sulphate crystals 

c) Displacement reaction     -iii) Iron nails kept in copper sulphate solution

d) Double displacement reaction   -(iv) Reaction between sodium sulphate and barium chloride solutions

(i) Action of water on quick lime

EXPERIMENT 1 (a)

Aim  

To perform and observe the action of water on quicklime and classify the reaction.

Materials Required 
Calcium oxide, water, beaker, glass rod, dropper, red litmus paper, test tube, filter paper, funnel. 

Theory
Quicklime reacts with water to form calcium hydroxide. As in this reaction two substances – quicklime and water combine to form a new substance, therefore, this reaction is called combination reaction. This chemical change can be represented by the given chemical equation:

During this chemical change, heat is also released. Therefore, this is also an example of exothermic reaction.

Procedure And Observation TableThe experimental procedure is described in the table:

ResultTwo compounds, viz. quicklime and water combine to form calcium hydroxide. Therefore, this reaction is an example of combination reaction.

Precautions 

1. Quicklime can cause severe burns, therefore, it should be handled with spatula.
2. As the reaction between quicklime and water is exothermic, water should be poured over quicklime slowly.
3. The filtrate collected should be clear.

EXPERIMENT 31b)

(ii) Action of heat on ferrous sulphate crystals 

Aim 
To perform and observe the action of heat on crystals of ferrous sulphate and classify the reaction.

Material Required 
Ferrous sulphate crystals, test tubes, test tube holder, blue limus paper.

TheoryThe crystals of ferrous sulphate are green in colour. When these crystals are heated, following reaction takes place.

In this reaction, a single reactant breaks down to give simple products. Therefore, this is a decomposition reaction.
Ferrous sulphate crystals (FeS0₄.7H₂0) lose water when heated and the colour of crystals changes. It then decomposes to ferric oxide(Fe₂0₃), sulphur dioxide (S0₂) and sulphur trioxide (S0₃). Ferric oxide is solid while S0₂ and S0₃ are gases. Both S0₂ and S0₃ are acidic and hence, these gases turn the blue litmus red. Sulphur dioxide can reduce an acidified solution of potassium dichromate. This reaction can be utilised to confirm the presence of sulphur dioxide.

Procedure And Observation Table 
The experimental procedure is given in the following table:

ResulstOn heating, ferrous sulphate decomposes to give ferric oxide, sulphur dioxide and sulphur trioxide. This decomposition reaction.

Precautions  

1. While heating ferrous sulphate, keep the mouth of test tube away from you and your classmates.

EXPERIMENT 1(c)

(iii) Iron nails kept in copper sulphate solution

AimTo perform and observe the reaction of iron nails kept in copper sulphate solution and classify the reaction.

Materials RequiredIron nails, copper sulphate solution, test tubes, test tube stand, sandpaper and thread.

TheoryWhen an iron nail is immersed in copper sulphate solution, following reaction takes place:

In the above reaction, iron ions (Fe²⁺) being more reactive displaces copper ions (Cu²⁺) and a new compound ferrous sulphate is formed. This type of reactions is called displacement reaction.

Procedure 

1. Take two iron nails and clean them by rubbing with sandpaper.
2. Take two test tubes and mark them as ‘A’ and ‘B’.
3. In each test tube, pour about 10 ml of copper sulphate solution.
4. Tie one iron nail with a thread and immerse this carefully in the copper sulphate solution in test tube A for about 20 minutes. Keep aside one nail for comparison.
5. After 20 minutes, take out the iron nail from the copper sulphate solution.
6. Compare the intensity of blue colour of copper sulphate solutions of both   the  test    tubes ‘A’ and ‘B\
7. Also, compare the colour of iron nail dipped in copper sulphate solution with one kept aside.
   

ObservationsThe initial colour of copper sulphate solution was blue which after immersing iron nails turns to light green.
The initial colour of iron nail was grey. After immersing the nail into copper sulphate solution, a brown coating developed over it. Because of this coating iron nail appears reddish brown.

ResultOn keeping the iron nails in copper sulphate solution, a displacement reaction takes place. In this displacement reaction, iron displaces copper and two new products ferrous sulphate and copper are formed.

Precautions 

1. The iron nails should be cleaned by rubbing them with a sandpaper.
2. The test tube containing iron nails and copper sulphate solution should not be disturbed.

EXPERIMENT 1(d)

(iv) Reaction between sodium sulphate and barium chloride solutions

AimTo perform and observe the reaction between sodium sulphate and barium chloride solutions and classify the reaction.

Materials RequiredSodium sulphate solution, barium chloride solution, test tubes, beaker.

TheoryWhen the solutions of sodium sulphate and barium chloride are mixed, a white precipitate of barium sulphate is formed. Chemical equation for this chemical change can be given as follows:

In this reaction, both sodium sulphate and barium chloride exchange ions. Hence, this type of reaction is called double displacement reaction.

Procedure 

1. Take 5 ml of sodium sulphate solution in a test tube and mark it as ‘A’.
2. Take 5 ml of barium chloride solution in another test tube and mark it as ‘B’.
3. Mix the solutions of test tubes ‘A’ and ‘B’ in a beaker.
4. With the help of a clean glass rod, stir the mixture kept in beaker.
5. Record your observation.

ObservationOn mixing the solutions of sodium sulphate and barium chloride, a white precipitate is formed.

ResultOn mixing the solutions of sodium sulphate and barium chloride, a double displacement reaction takes place.
In this reaction sodium sulphate and barium chloride exchange ions and new products barium sulphate (white ppt) and sodium chloride are formed.

Precautions                                                                                                                                   –

1. Test tubes, beaker and glass rod should be cleaned.
2. Equal volumes of sodium sulphate and barium chloride solutions should be used.

EXPERIMENT-2...BEGIN FROM THE NEW PAGE

AIMTo find the pH of the following samples by using pH paper/universal indicator:

1. Dilute hydrochloric acid (HCl)
2. Dilute sodium hydroxide  (NaOH) solution
3. Dilute ethanoic acid (CH₃COOH) solution
4. Lemon juice
5. Water
6. Dilute sodium bicarbonate (NaHCO₃) solution.

MATERIALS REQUIREDTest tubes, test tube stand, droppers or glass rod, pH paper/universal indicator, standard colour chart, glazed white tile and samples of dil. HCl, dil. NaOH, dil. ethanoic acid (acetic acid/vinegar), lemon juice, distilled water and dil. sodium bicarbonate solution.

THEORY

1. pH is the measure of hydrogen ion concentration of a solution.
2. The hydrogen ion concentration (H⁺) for an acidic solution is always greater than 10^-7 mol L^-1 and its pH is, therefore, always less than 7.
3. The hydrogen ion concentration of a basic solution is always less than 10^-7 mol L^-1 and, therefore, its pH is always greater than 7.
4. The hydrogen ion concentration of a neutral solution is 10^-7 mol L^-1 and, therefore, its pH is 7.
5. The pH of a solution can be measured by using a pH paper, universal indicator or pH meter.

PROCEDURE

1. Take the given solutions in separate test tubes marked as A, B, C, D, E and F and keep them in the test tube stand.
   
2. Take six strips of pH paper and place them on a glazed white tile.
3. Using a dropper or a glass rod, place a drop of the test solution on the pH paper.
4. Note the colour developed on the pH paper and compare it with the colour chart of the pH paper.
5. Record the pH value corresponding to the colour.                                                                         .
6. Similarly, using a fresh dropper each time, perform the experiment with the remaining test samples using a fresh strip of pH paper.
7. Record your observations as indicated in the table below.
8. For using universal indicator, add a few drops of universal indicator to each of the test tubes with the test solutions.
9. Note the colour of each solution and compare it with colour on the indicator bottle.
10. Record your observations.

OBSERVATION TABLE

RESULT

1. The pH of dilute solutions of hydrochloric acid, ethanoic acid and lemon juice is less than 7 and therefore, they are acidic in nature.
2. The pH of dilute solutions of sodium hydroxide and sodium bicarbonate is more than 7 and therefore, these solutions are basic in nature.
3. The pH of water is 7 and therefore, it is neutral in nature.

PRECAUTIONS

1. Mark the test tubes carefully.
2. Use distilled water for preparing solutions.
3. Use only standard colour charts supplied with the pH paper for assessing the pH value.
4. Do not touch the pH paper with unclean and wet hands.
5. Keep the pH paper away from chemical fumes. .
6. Do not touch or taste the solutions.
7. Clean the glass rod/dropper properly before reusing.
8. Do not waste pH paper.