Class 10 Notes

Class 10 Science Notes Chapter 4 (Chapter 4) – Lab Manual (English) Book

Philoid

Philoid

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Lab Manual (English)
Detailed Notes with MCQs of the key experiments from Chapter 4 of your Lab Manual. These experiments are crucial for understanding chemical reactions and properties of common substances, and frequently appear in examinations. Pay close attention to the procedures, observations, and the conclusions drawn.

Chapter 4: Studying Chemical Reactions and Properties

This chapter primarily deals with experiments demonstrating:

  1. Properties of Acids (HCl) and Bases (NaOH).
  2. Determination of pH using Universal Indicator/pH paper.
  3. Comparing the reactivity of different metals.
  4. Observing different types of chemical reactions.

Experiment 1: Properties of Acids (HCl) and Bases (NaOH)

  • Aim: To study the properties of acids (dilute HCl) and bases (dilute NaOH) by observing their reactions with litmus solution/paper, zinc metal, and solid sodium carbonate.

  • Materials: Dilute HCl, Dilute NaOH, Blue litmus solution/paper, Red litmus solution/paper, Zinc granules, Solid sodium carbonate (Na₂CO₃), Test tubes, Dropper, Delivery tube, etc.

  • Procedure & Observations:

    Test Substance Reagent Added Observation Inference/Chemical Equation
    Blue Litmus Dil. HCl Turns Red HCl is acidic.
    Red Litmus Dil. HCl No change HCl is acidic.
    Blue Litmus Dil. NaOH No change NaOH is basic.
    Red Litmus Dil. NaOH Turns Blue NaOH is basic.
    Zinc Granules Dil. HCl Colourless, odourless gas evolves. Gas burns with a 'pop' sound near a flame. Hydrogen gas (H₂) is produced.
    Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)
    Zinc Granules Dil. NaOH Colourless, odourless gas evolves (slower). Gas burns with a 'pop' sound. Hydrogen gas (H₂) is produced.
    Zn(s) + 2NaOH(aq) → Na₂ZnO₂(aq) + H₂(g)
    (Sodium Zincate)
    Solid Na₂CO₃ Dil. HCl Brisk effervescence. Colourless, odourless gas evolves, turns lime water milky. Carbon dioxide (CO₂) gas is produced.
    Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)
    CO₂(g) + Ca(OH)₂(aq) → CaCO₃(s)↓ + H₂O(l)
    Solid Na₂CO₃ Dil. NaOH No observable reaction. Bases generally do not react with carbonates/bicarbonates.

  • Key Takeaways:

    • Acids turn blue litmus red. Bases turn red litmus blue.
    • Acids react with active metals (like Zn) to produce Hydrogen gas.
    • Strong bases (like NaOH) also react with active metals (like Zn) to produce Hydrogen gas.
    • Acids react with metal carbonates and bicarbonates to produce Carbon Dioxide gas, which turns lime water milky. Bases do not react with carbonates.

  • Precautions: Handle acids and bases with care, they are corrosive. Use a small quantity of reactants. When testing for H₂ gas, perform the 'pop' sound test carefully.

Experiment 2: Determining pH

  • Aim: To find the pH of given samples (dil. HCl, dil. NaOH, dil. Ethanoic acid, Lemon juice, Water, dil. Sodium bicarbonate solution) using pH paper or universal indicator solution.

  • Materials: pH paper strips/Universal indicator solution, Glass rod, Dropper, White tile/Test tubes, Given sample solutions.

  • Procedure: Place a drop of the sample solution on the pH paper or add a few drops of universal indicator to the solution in a test tube. Match the colour produced with the standard pH colour chart.

  • Observations (Approximate Values):

    Sample Solution Colour on pH Paper/Indicator Approximate pH Nature
    Dilute HCl Red 1 - 2 Strongly Acidic
    Dilute NaOH Dark Blue/Violet 13 - 14 Strongly Basic
    Dilute Ethanoic Acid (CH₃COOH) Orange/Yellowish-Orange 3 - 4 Weakly Acidic
    Lemon Juice Pinkish-Red/Orange 2 - 3 Acidic
    Water (Distilled) Green 7 Neutral
    Dil. Sodium Bicarbonate (NaHCO₃) Bluish-Green/Blue 8 - 9 Weakly Basic

  • Key Takeaways:

    • pH scale ranges from 0 to 14.
    • pH < 7 indicates an acidic solution. Lower the pH, stronger the acid.
    • pH = 7 indicates a neutral solution.
    • pH > 7 indicates a basic solution. Higher the pH, stronger the base.
    • Universal indicator gives different colours at different pH values.

Experiment 3: Reactivity Series

  • Aim: To arrange the metals Iron (Fe), Copper (Cu), Zinc (Zn), and Aluminium (Al) in decreasing order of reactivity based on their reaction with salt solutions (FeSO₄, CuSO₄, ZnSO₄, Al₂(SO₄)₃).
  • Materials: Metal strips/pieces (Fe, Cu, Zn, Al), Aqueous solutions of FeSO₄, CuSO₄, ZnSO₄, Al₂(SO₄)₃, Test tubes, Sandpaper (to clean metal surfaces).
  • Procedure: Clean the metal strips. Place a metal strip in a test tube containing the salt solution of another metal. Observe for any changes (colour change of solution, deposition on metal strip) after some time.
  • Observations (Simplified Summary):
    • Aluminium (Al): Displaces Fe from FeSO₄, Cu from CuSO₄, Zn from ZnSO₄. (Most reactive among these).
    • Zinc (Zn): Displaces Fe from FeSO₄, Cu from CuSO₄. Does not displace Al from Al₂(SO₄)₃.
    • Iron (Fe): Displaces Cu from CuSO₄. Does not displace Al from Al₂(SO₄)₃ or Zn from ZnSO₄.
    • Copper (Cu): Does not displace Al, Zn, or Fe from their respective salt solutions. (Least reactive among these).
  • Inference: A more reactive metal displaces a less reactive metal from its salt solution.
  • Reactivity Order (Decreasing): Al > Zn > Fe > Cu
  • Example Equation: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s) (Blue solution fades, reddish-brown copper deposits on zinc strip).

Experiment 4: Types of Chemical Reactions

  • Aim: To perform and observe different types of chemical reactions: Combination, Decomposition, Displacement, Double Displacement.

    1. Combination Reaction:

      • Procedure: Take a small amount of Calcium Oxide (CaO, quicklime) in a beaker. Slowly add water to it. Touch the beaker carefully.
      • Observation: Hissing sound is produced, the beaker becomes hot, a suspension (calcium hydroxide, slaked lime) is formed.
      • Equation: CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
      • Type: Combination (Exothermic)

    2. Decomposition Reaction (Heating Ferrous Sulphate):

      • Procedure: Heat about 2g of green ferrous sulphate crystals (FeSO₄·7H₂O) in a dry boiling tube. Observe colour changes and smell any gas evolved (carefully waft).
      • Observation: Green crystals first lose water (become white anhydrous FeSO₄), then decompose on further heating to form a reddish-brown solid (Fe₂O₃). Gases with the characteristic smell of burning sulphur (SO₂ and SO₃) are evolved.
      • Equation: 2FeSO₄(s) --Heat--> Fe₂O₃(s) + SO₂(g) + SO₃(g)
      • Type: Thermal Decomposition

    3. Displacement Reaction:

      • Procedure: Take copper sulphate (CuSO₄) solution (blue) in a test tube. Place a clean iron nail in it. Observe after 10-15 minutes.
      • Observation: The blue colour of the solution fades (turns light green), and a reddish-brown coating (Copper metal) deposits on the iron nail.
      • Equation: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)
      • Type: Displacement (Fe is more reactive than Cu)

    4. Double Displacement Reaction (Precipitation):

      • Procedure: Take sodium sulphate (Na₂SO₄) solution in one test tube and barium chloride (BaCl₂) solution in another. Mix the two solutions.
      • Observation: A white, insoluble substance (precipitate) of Barium Sulphate (BaSO₄) is formed immediately.
      • Equation: Na₂SO₄(aq) + BaCl₂(aq) → BaSO₄(s)↓ + 2NaCl(aq)
      • Type: Double Displacement (Precipitation Reaction)

  • Key Takeaways: Understand how to identify each reaction type based on the reactants and products (e.g., single product in combination, single reactant breaking down in decomposition, displacement of one element by another, exchange of ions in double displacement).

Multiple Choice Questions (MCQs)

  1. When dilute HCl is added to zinc granules, the gas evolved:
    a) Turns lime water milky
    b) Burns with a 'pop' sound
    c) Has a pungent smell
    d) Is reddish-brown in colour

  2. A student tested the pH of distilled water and found that the colour of the pH paper changed to green. He then tested the pH of dilute NaOH solution. The colour of the pH paper would likely change to:
    a) Red
    b) Yellow
    c) Blue
    d) Orange

  3. Which of the following reactions is a double displacement reaction?
    a) CaO + H₂O → Ca(OH)₂
    b) 2FeSO₄ → Fe₂O₃ + SO₂ + SO₃
    c) Zn + CuSO₄ → ZnSO₄ + Cu
    d) AgNO₃ + NaCl → AgCl + NaNO₃

  4. When iron nails are added to copper sulphate solution, the observation made after some time is:
    a) The solution turns colourless and the nail remains unchanged.
    b) The solution remains blue and a grey coating forms on the nail.
    c) The solution turns light green and a brown coating forms on the nail.
    d) The solution turns blue and the nail dissolves completely.

  5. Heating ferrous sulphate crystals strongly results in the formation of:
    a) A green residue and SO₂ gas
    b) A white residue and SO₃ gas
    c) A reddish-brown residue and gases smelling like burning sulphur
    d) A yellow residue and O₂ gas

  6. Which of the following solutions will turn red litmus blue?
    a) Lemon juice
    b) Dilute HCl
    c) Dilute Sodium Bicarbonate solution
    d) Distilled water

  7. A metal 'M' reacts with CuSO₄ solution to form MSO₄ and Cu. It does not react with ZnSO₄ solution. Identify the correct order of reactivity.
    a) M > Cu > Zn
    b) Zn > M > Cu
    c) Cu > Zn > M
    d) Zn > Cu > M

  8. The reaction between Sodium Sulphate solution and Barium Chloride solution is an example of:
    a) Combination reaction
    b) Decomposition reaction
    c) Displacement reaction
    d) Precipitation reaction

  9. Brisk effervescence is observed when dilute HCl is added to:
    a) Zinc granules
    b) Solid Sodium Chloride
    c) Solid Sodium Carbonate
    d) Copper turnings

  10. A solution turns universal indicator orange. Its approximate pH is likely to be:
    a) 1
    b) 4
    c) 7
    d) 10

Answer Key for MCQs:

  1. b
  2. c
  3. d
  4. c
  5. c
  6. c
  7. b (M displaces Cu, so M > Cu. M does not displace Zn, so Zn > M. Hence, Zn > M > Cu)
  8. d (It's also double displacement, but precipitation is a more specific observation here)
  9. c
  10. b

Study these notes thoroughly, focusing on the observations and the chemical principles behind them. Good luck with your preparation!

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