Chapter 5 Solutions — Exploring Mixtures and their Separation

Revise, Reflect, Refine

1. 1.
   Which of the following mixtures are correctly classified as homogeneous (Hm) and heterogeneous (Ht)? Choose the correct option.

   • (i) Air — Hm, Milk — Ht, Sugar solution — Hm, Smoke — Hm
   • (ii) Brass — Ht, Fog — Ht, Vinegar — Ht, Muddy water — Hm
   • (iii) Copper sulfate solution — Hm, Salt solution — Hm, Milk — Hm, Bronze — Hm
   • (iv) Muddy water — Ht, Milk — Ht, Blood — Ht, Brass — Hm
2. 2.
   Choose the correct options, and explain the reason for the correct and incorrect options. Which among the following mixtures show the Tyndall Effect? A mixture of:

   • (a) air and dust particles
   • (b) copper sulfate and water
   • (c) starch and water
   • (d) acetone and water
   • (i) a and b
   • (ii) b and d
   • (iii) a and c
   • (iv) c and d
3. 3.
   A mixture can be categorised as a solution, a suspension, or a colloid, each possessing distinct properties. Utilise the words or phrases provided in the box to fill in Table 5.2. Words and Phrases: Large-sized particles; Particles remain evenly distributed; Small-sized particles (less than 1 nm diameter); Moderate-sized particles (1–1000 nm); Settles down when left undisturbed (more than 1000…
4. 4.
   Solve the following problems:

   • (i) A cake recipe uses dry ingredients, namely 75 g of sugar for 420 g of all-purpose flour and 5 g of sodium hydrogencarbonate. Express the concentration of each component in the mixture using an appropriate method.
   • (ii) A brass alloy contains 70% copper by mass. Calculate the quantities of copper and zinc present in 120 g of brass.
5. 5.
   The label on a cooking oil pack says one litre (910 g). If this oil is mixed with water, will it form a separate layer? If so, which substance will be on top? How will you separate the two layers? Also, draw the diagram of the apparatus used.
6. 6.
   Assertion (A): Solutions do not exhibit the Tyndall effect. Reason (R): The particles in solutions are larger than 100 nm, so they cannot scatter light. Choose the correct option:

   • (i) Both A and R are true, and R is the correct explanation of A.
   • (ii) Both A and R are true, but R is not the correct explanation of A.
   • (iii) A is true, but R is false.
   • (iv) A is false, but R is true.
7. 7.
   How would you separate the mixtures given in Table 5.3? Mention the reason for choosing your method. If a mixture cannot be separated, explain why. Mixtures: Mud from muddy water | Plasma from other components in the blood sample | Naphthalene and sand | Chalk powder and common salt | Common salt and water | Oil from water | Pigments of the flower
8. 8.
   Two miscible liquids, A and B, are present in a mixture. The boiling point of A is 60 °C and the boiling point of B is 90 °C. Suggest a method to separate them. Also, draw a labelled diagram of the method suggested.
9. 9.
   Compare evaporation, crystallisation and distillation. In which situation, would you prefer each of these over the others?
10. 10.
    Blood is an example of a colloidal mixture.

    • (i) What would happen if blood behaved like a true suspension inside the body?
    • (ii) In a blood sample, identify the dispersed phase and the dispersion medium.
11. 11.
    You are given a mixture of sand, common salt and naphthalene (Fig. 5.25a). The Fig. 5.25b depicts various steps (labelled 1, 2, 3) used to separate the components of this mixture. Identify and write down the correct sequence of separation techniques.
12. 12.
    Why is distillation an effective method for separating a mixture of water and acetone?
13. 13.
    Answer the following questions with the help of the data given in Table 5.4 (Solubility of various salts in g per 100 g of water at different temperatures): Table 5.4 — KNO3: 10°C=21, 20°C=32, 30°C=45, 40°C=62, 60°C=106, 80°C=167; NaCl: 10°C=36, 20°C=36, 30°C=36.3, 40°C=36.5, 60°C=37, 80°C=37; KCl: 10°C=35, 20°C=35, 30°C=37.4, 40°C=40, 60°C=46, 80°C=54; NH4Cl: 10°C=24, 20°C=37, 30°C=41, 40°C=41…
14. 14.
    Three students, A, B and C, are preparing sugar solutions for an experiment: - Student A dissolves 20 g of sugar in 80 g of water. - Student B dissolves 20 g of sugar in 100 g of water. - Student C dissolves 30 g of sugar in 80 g of water.

    • (i) Calculate the mass percentage (% m/m) concentration of sugar in each student's solution.
    • (ii) Whose solution is the most concentrated? Explain why.
15. 15.
    Examine Fig. 5.26.

    • (i) Identify the separation technique marked as 'S'.
    • (ii) Label the apparatus A, B and C.
    • (iii) Which of the following mixtures can be separated by the technique identified above? Use the data given in Table 5.5. Mixtures:
    • (a) water — acetone,
    • (b) water — salt,
    • (c) acetone — alcohol,
    • (d) sand — salt,
    • (e) alcohol — chloroform,
    • (f) alcohol — benzene. Table 5.5: Boiling points…