Class 10 CBSE Board Experiments / Practicals - Science Chemistry

Experiment No. - 01

Objective: To determine the pH of the following samples using pH paper or a universal indicator.

Experiment No. - 02

Objective

To study the properties of acids (HCl) and bases (NaOH) based on their reactions with:

1. Litmus solution (Blue/Red)

2. Zinc metal

3. Solid sodium carbonate

Experiment No. - 03

Performing and observing the following reactions and classifying them into:

A. Combination reaction

B. Decomposition reaction

C. Displacement reaction

D. Double displacement reaction

(i) Action of water on quicklime

(ii) Action of heat on ferrous sulphate crystals

(iii) Iron nails kept in copper sulphate solution

(iv) Reaction between sodium sulphate and barium chloride solutions

Experiment No. - 04

Observing the action of Zn, Fe, Cu and Al metals on the following salt solutions.

i) ZnSO4(aq)

ii) FeSO4(aq)

iii) CuSO4(aq)

iv) Al2 (SO4)3(aq)

Arranging Zn, Fe, Cu and Al (metals) in the decreasing order of reactivity based on the above result.

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Experiment No. - 01

Objective: To determine the pH of the following samples using pH paper or a universal indicator:

1. Dilute Hydrochloric Acid

2. Dilute NaOH solution

3. Dilute Ethanoic Acid solution

4. Lemon juice

5. Water

6. Dilute Hydrogen Carbonate solution

Materials Required:

• pH paper or Universal Indicator

• Dilute Hydrochloric Acid (HCl)

• Dilute NaOH solution

• Dilute Ethanoic Acid (CH₃COOH) solution

• Lemon juice

• Distilled water

• Dilute Hydrogen Carbonate (NaHCO₃) solution

Procedure:

1. Take a small sample of each solution (HCl, NaOH, Ethanoic Acid, Lemon Juice, Water, Hydrogen Carbonate solution) in separate test tubes or beakers.

2. Dip a strip of pH paper or add a few drops of universal indicator to each sample.

3. Observe the colour change of the pH paper or the indicator solution.

4. Compare the colour developed with the colour chart provided with the universal indicator or pH paper.

5. Record the pH value corresponding to the observed colour for each sample.

Observations:

Inferences:

1. Dilute Hydrochloric Acid (HCl): The pH value is between 1-2, indicating that HCl is a strong acid.

2. Dilute NaOH solution: The pH value is between 12-13, indicating that NaOH is a strong base.

3. Dilute Ethanoic Acid (CH₃COOH): The pH value is between 4-5, indicating that Ethanoic Acid is a weak acid.

4. Lemon juice: The pH value is between 2-3, indicating that lemon juice is an acidic solution, due to the presence of citric acid.

5. Water: The pH value is 7, indicating that water is neutral.

6. Dilute Hydrogen Carbonate (NaHCO₃): The pH value is between 8-9, indicating that NaHCO₃ is a weak base.

Conclusion:

The pH of different substances varies depending on their acidic or basic nature. Strong acids like HCl have a very low pH, while strong bases like NaOH have a high pH. Weak acids and weak bases fall in between. Water, being neutral, has a pH of 7. This experiment highlights the importance of pH in determining the nature of a substance, whether it is acidic, neutral, or basic.

Precautions:

1. Use Fresh Samples: Always use fresh samples of each solution to ensure accurate results. Old or contaminated samples may give inaccurate pH readings.

2. Avoid Cross-Contamination: When testing multiple samples, ensure that the pH paper or universal indicator dropper is not contaminated by the solutions from previous tests. Use a clean pipette or tongs to handle each sample.

3. Properly Handle Acids and Bases:

   • Handle hydrochloric acid and NaOH with care, as they are corrosive. Always wear gloves and safety goggles while performing the experiment.

   • In case of skin contact with acid or base, wash immediately with plenty of water.

4. Use Distilled Water for Neutral Sample: When testing water, make sure it is distilled or deionized to avoid any interference from dissolved minerals or impurities.

5. Correct Reading of pH Paper: After dipping the pH paper into the solution, allow it to rest for a few seconds to develop the colour fully before comparing it with the pH chart.

6. Avoid Over-Concentration of Solutions: Ensure that the acid and base solutions are dilute, as concentrated solutions may lead to dangerous reactions or incorrect readings due to their extreme pH.

7. Store Solutions Properly: Store all chemicals (especially acids and bases) in appropriately labelled containers and in a safe location, away from direct sunlight or extreme temperatures.

8. Dispose of Chemicals Properly: Dispose of the acid, base, and other chemical solutions as per the laboratory's waste disposal guidelines. Do not pour them down the drain unless instructed by your teacher or lab supervisor.

9. Clean Equipment Thoroughly: After the experiment, wash all used glassware and equipment with water to prevent contamination for future experiments.

Experiment No. - 02

Objective

To study the properties of acids (HCl) and bases (NaOH) based on their reactions with:

1. Litmus solution (Blue/Red)

2. Zinc metal

3. Solid sodium carbonate

Materials Required

• Hydrochloric acid (HCl)

• Sodium hydroxide (NaOH)

• Blue litmus solution

• Red litmus solution

• Zinc metal granules

• Solid sodium carbonate (Na₂CO₃)

• Test tubes

• Test tube stand

• Dropper

Procedure, Observations, and Inferences

1. Reaction with Litmus Solution

2. Reaction with Zinc Metal

3. Reaction with Solid Sodium Carbonate (Na₂CO₃)

Conclusion

1. Acids like HCl turn blue litmus red, produce hydrogen gas with zinc, and release CO₂ when reacting with sodium carbonate.

2. Bases like NaOH turn red litmus blue and show no significant reaction with zinc or sodium carbonate under normal conditions.

Precautions

1. Handle acids and bases with care; wear gloves and safety goggles.

2. Do not inhale gases directly; use proper ventilation or fume hood.

3. Clean all apparatus after the experiment.

Experiment No. - 03

Experiment: Classification of Chemical Reactions

(i) Action of water on quicklime

• Chemical Reaction:

  
  

  CaO (quicklime) + H2O → Ca(OH)2 

• Observation:

  
  

  When water is added to quicklime, a vigorous reaction occurs, releasing heat. The mixture forms a white, slaked lime paste.

• Inference:

  
  

  This is a combination reaction as two reactants combine to form a single product.

(ii) Action of heat on ferrous sulphate crystals

• Chemical Reaction:

  
  

  2FeSO4Fe2O3+SO2+SO3

• Observation:

  
  

  On heating ferrous sulphate crystals, they lose water of crystallization and change from green to white, followed by decomposition to form reddish-brown residue with the release of a pungent gas.

• Inference:

  
  

  This is a decomposition reaction as a single compound breaks into multiple products.

(iii) Iron nails kept in copper sulphate solution

• Chemical Reaction:

  
  

  Fe (Iron) + CuSO4 → FeSO4 + Cu (Copper)

• Observation:

  
  

  Iron nails become coated with a reddish-brown layer of copper, and the blue color of copper sulphate solution fades to green.

• Inference:

  
  

  This is a displacement reaction as iron displaces copper from copper sulphate.

(iv) Reaction between sodium sulphate and barium chloride solutions

• Chemical Reaction:

  
  

  Na2SO4 + BaCl2→BaSO4 (white precipitate) + 2NaCl

• Observation:

  
  

  When the two solutions are mixed, a white precipitate of barium sulphate forms.

• Inference:

  
  

  This is a double displacement reaction as ions are exchanged between the two reactants to form new products.

Summary Table

Precautions

General Precautions for All Reactions:

1. Wear safety gear: Always wear a lab coat, gloves, and safety goggles to protect yourself.

2. Handle chemicals carefully: Avoid direct contact with chemicals and use a spatula or droppers for transfer.

3. Avoid inhalation: Perform reactions involving gases (e.g., SO₂) in a well-ventilated area or under a fume hood.

4. Dispose of chemicals properly: Follow proper guidelines for the disposal of chemical waste.

Specific Precautions for Each Reaction:

1. Action of water on quicklime:

   • Add water to quicklime slowly and carefully as the reaction is exothermic and can cause splattering.

   • Use a heat-resistant container to avoid breakage due to heat generation.

2. Action of heat on ferrous sulphate crystals:

   • Heat the ferrous sulphate crystals gently to avoid uncontrolled decomposition.

   • Conduct the reaction in a fume hood to avoid inhaling harmful gases like SO₂ and SO₃.

3. Iron nails in copper sulphate solution:

   • Avoid prolonged exposure to copper sulphate as it is toxic and can cause skin irritation.

   • Use clean and dry iron nails for accurate observations.

4. Reaction between sodium sulphate and barium chloride solutions:

   • Measure solutions accurately to avoid wastage and ensure proper reaction.

   • Dispose of the precipitate (barium sulphate) carefully, as it is insoluble and can pollute the environment.

Experiment No. - 04

Aim

To study the action of metals Zn, Fe, Cu, and Al with different salt solutions and arrange them in decreasing order of reactivity.

Materials Required

• Zinc metal (Zn)

• Iron metal (Fe)

• Copper metal (Cu)

• Aluminium metal (Al)

• Aqueous solutions of:

  
  

  i) Zinc sulfate (ZnSO₄)

  
  

  ii) Iron sulfate (FeSO₄)

  
  

  iii) Copper sulfate (CuSO₄)

  
  

  iv) Aluminium sulfate (Al₂(SO₄)₃)

• Test tubes

• Dropper

Procedure

1. Take four test tubes and label them as A, B, C, and D.

2. Pour 5 mL of ZnSO₄ solution into test tube A, FeSO₄ into test tube B, CuSO₄ into test tube C, and Al₂(SO₄)₃ into test tube D.

3. Add a small strip or granules of zinc to each test tube. Observe and note any reaction.

4. Repeat the above steps for iron, copper, and aluminium, each time using a fresh set of test tubes and solutions.

5. Record the observations in the table.

Observation Table

Inference

1. Zinc (Zn) reacts with FeSO₄ and CuSO₄, displacing Fe and Cu, but does not react with ZnSO₄ or Al₂(SO₄)₃.

2. Iron (Fe) reacts only with CuSO₄, displacing Cu, and shows no reaction with ZnSO₄, FeSO₄, or Al₂(SO₄)₃.

3. Copper (Cu) does not react with any of the solutions, indicating it is the least reactive.

4. Aluminium (Al) reacts with ZnSO₄, FeSO₄, and CuSO₄, displacing the respective metals, but does not react with its own salt solution Al₂(SO₄)₃.

Conclusion

Based on the observations, the decreasing order of reactivity of the metals is:

Al > Zn > Fe > Cu

This indicates that aluminium is the most reactive and copper is the least reactive among the given metals.

Precautions

1. Use clean and dry test tubes to avoid contamination of solutions.

2. Handle chemicals and metals carefully using tongs or gloves to avoid skin contact.

3. Add the metal pieces slowly to the solutions to prevent splashing.

4. Perform the experiment in a well-ventilated area or under a fume hood.

5. Dispose of the metal residues and solutions properly as per laboratory waste disposal guidelines.

6. Wash your hands thoroughly after handling chemicals and metals.

7. Record observations immediately to avoid missing any changes.