ICSE Class 10

General instructions: Answer all questions. Marks are shown in brackets [ ].

Objective

1. 1.
   Pure water consists almost entirely of which of the following?

   1. A. Ions
   2. B. Molecules
   3. C. Electrons
   4. D. Protons
   [1]
2. 2.
   What does it mean if an electrolyte is described as a 'strong electrolyte'?

   1. A. It partially ionizes in solution, allowing limited current flow.
   2. B. It completely ionizes in molten or aqueous state, allowing large current flow.
   3. C. It does not conduct electricity at all.
   4. D. It conducts electricity only in solid state.
   [1]
3. 3.
   The inert electrode used in the electrolysis of acidified water is:

   1. a. Nickel
   2. b. Platinum
   3. c. Copper
   4. d. Silver
   [1]
4. 4.
   Why does an aqueous solution of sodium chloride conduct electricity?

   1. A. Sodium chloride dissociates into free Na⁺ and Cl⁻ ions in water, allowing current flow.
   2. B. Sodium chloride reacts with water to form a covalent compound that conducts electricity.
   3. C. Sodium chloride molecules move freely in water, carrying electric charge.
   4. D. Sodium chloride dissolves in water to form a non-electrolyte solution.
   [1]
5. 5.
   Which term describes the process of separation of ions present in an ionic compound?

   1. A. Ionization
   2. B. Dissociation
   3. C. Hydrolysis
   4. D. Neutralization
   [1]
6. 6.
   Pure metal is made during electro-refining.

   1. A. Cathode
   2. B. Anode
   3. C. Electrolyte
   4. D. None of these
   [1]
7. 7.
   During electrolysis, if electrons are being added to an element Y, towards which electrode will Y migrate?

   1. A. Anode
   2. B. Cathode
   3. C. Neither electrode
   4. D. Both electrodes
   [1]
8. 8.
   Differentiate between strong electrolytes and weak electrolytes based on the following criteria. Which of the given options correctly represents their characteristics? 1. Conductivity 2. Degree of dissociation 3. State of particles in solution 4. Example of bulb glow

   1. A. Strong electrolytes are poor conductors, partially dissociated, contain mostly molecules, and cause dim bulb glow. Weak electrolytes are good conductors, fully dissociated, contain only ions, and cause bright bulb glow.
   2. B. Strong electrolytes are good conductors, almost fully dissociated, contain mostly free ions, and cause bright bulb glow. Weak electrolytes are poor conductors, partially dissociated, contain both ions and molecules, and cause dim bulb glow.
   3. C. Strong electrolytes conduct no electricity, remain undissociated, contain only molecules, and cause no bulb glow. Weak electrolytes conduct moderately, dissociate fully, contain only ions, and cause moderate bulb glow.
   4. D. Strong electrolytes are good conductors, partially dissociated, contain both ions and molecules, and cause dim bulb glow. Weak electrolytes are poor conductors, fully dissociated, contain only ions, and cause bright bulb glow.
   [1]
9. 9.
   The ______ the concentration of an ion in a solution, the greater is the probability of it being discharged at its appropriate electrode.

   1. A. higher
   2. B. lower
   3. C. neutral
   4. D. constant
   [1]
10. 10.
    Why is electrolysis considered an example of a redox reaction?

    1. A. It involves only oxidation at both electrodes.
    2. B. Oxidation occurs at the anode and reduction at the cathode.
    3. C. It does not involve electron transfer.
    4. D. Reduction occurs at the anode and oxidation at the cathode.
    [1]
11. 11.
    What product is formed at the anode during the electrolysis of acidified water using platinum electrodes?

    1. A. Oxygen
    2. B. Hydrogen
    3. C. Chlorine
    4. D. Platinum oxide
    [1]
12. 12.
    During the electrolysis of sodium chloride, explain the dissociation process and provide the reactions occurring at the cathode and anode. Which of the following correctly represents the overall process and electrode reactions?

    1. A. NaCl dissociates into Na⁺ and Cl⁻. At the cathode: Na⁺ + e⁻ → Na; at the anode: Cl⁻ - e⁻ → Cl, then Cl + Cl → Cl₂. Overall: 2NaCl → 2Na + Cl₂.
    2. B. NaCl dissociates into Na⁻ and Cl⁺. At the cathode: Cl⁺ + e⁻ → Cl; at the anode: Na⁻ - e⁻ → Na. Overall: 2NaCl → Na₂ + Cl₂.
    3. C. NaCl dissociates into Na⁺ and Cl⁻. At the cathode: Cl⁻ + e⁻ → Cl; at the anode: Na⁺ - e⁻ → Na. Overall: NaCl → Na + Cl.
    4. D. NaCl dissociates into Na and Cl atoms. At the cathode: Na → Na⁺ + e⁻; at the anode: Cl → Cl⁻ - e⁻. Overall: 2NaCl → 2Na⁺ + 2Cl⁻.
    [1]
13. 13.
    Which electrode is the oxidising electrode during electrolysis and why?

    1. A. Cathode, because reduction occurs there.
    2. B. Anode, because oxidation occurs there.
    3. C. Both electrodes, as both oxidation and reduction occur.
    4. D. Neither, as oxidation occurs in the electrolyte.
    [1]
14. 14.
    Three different electrolytic cells A, B and C are connected in separate circuits. Electrolytic cell A contains sodium chloride solution and the bulb in the circuit glows brightly. Electrolytic cell B contains acetic acid solution and the bulb glows dimly. Electrolytic cell C contains sugar solution and the bulb does not glow. Which of the following best explains these observations?

    1. A. Cell A has complete dissociation, Cell B has partial dissociation, and Cell C has no dissociation.
    2. B. Cell A is a weak electrolyte, Cell B is a strong electrolyte, and Cell C is a non-electrolyte.
    3. C. Cell A and Cell B both have complete dissociation, but Cell C has impurities blocking conduction.
    4. D. Cell A and Cell C are strong electrolytes, while Cell B is a non-electrolyte.
    [1]
15. 15.
    Which of the following correctly differentiates a strong electrolyte from an electrolyte (weak) based on dissociation and particle content?

    1. A. Strong electrolytes partially dissociate and contain ions only; electrolytes fully dissociate and contain ions and molecules.
    2. B. Strong electrolytes fully dissociate and contain ions only; electrolytes partially dissociate and contain ions and molecules.
    3. C. Both fully dissociate, but strong electrolytes contain ions only while electrolytes contain molecules only.
    4. D. Strong electrolytes do not dissociate; electrolytes fully dissociate and contain ions only.
    [1]
16. 16.
    The equation below shows the reaction between element X and dilute sulphuric acid. X(s) + H₂SO₄(aq.) → XSO₄(aq.) + H₂(g) Which particles are responsible for conducting electricity in dilute sulphuric acid and compound XSO₄?

    1. a. Electrons
    2. b. Only positive ions
    3. c. Only negative ions
    4. d. Both positive and negative ions
    [1]
17. 17.
    Molten lead bromide conducts electricity. It is called an _______. It is made up of lead _______ and bromide _______. Which set of terms correctly completes the blanks in order?

    1. A. electrolyte, cations, anions, positively, cations, negatively, anions
    2. B. conductor, atoms, molecules, neutrally, atoms, neutrally, molecules
    3. C. insulator, electrons, protons, negatively, anions, positively, cations
    4. D. solution, ions, ions, negatively, anions, positively, cations
    [1]
18. 18.
    Why does the concentration of sulphuric acid increase at the anode during the electrolysis of acidified water?

    1. A. H⁺ ions are discharged at the anode, leaving excess SO₄²⁻ ions to form H₂SO₄.
    2. B. Discharge of OH⁻ ions disturbs the ionic equilibrium of water, causing more water to ionise and produce excess H⁺ ions that combine with SO₄²⁻ ions.
    3. C. SO₄²⁻ ions are directly oxidized at the anode to form H₂SO₄.
    4. D. Water molecules split at the anode to release H₂SO₄ directly.
    [1]
19. 19.
    Why is the electrolysis of acidulated water considered an example of catalysis?

    1. A. The acid decomposes water into hydrogen and oxygen.
    2. B. The acid speeds up the reaction without being consumed.
    3. C. The acid reacts with water to form a new compound.
    4. D. The acid prevents the formation of hydrogen gas.
    [1]
20. 20.
    When a dilute aqueous solution of sodium chloride is electrolysed between platinum electrodes, why is hydrogen gas evolved at the cathode instead of sodium metal?

    1. A. Hydrogen is below sodium in the activity series, so it is preferentially discharged.
    2. B. Sodium ions are not present in the solution.
    3. C. Platinum electrodes react with sodium to form hydrogen.
    4. D. The solution is too concentrated for sodium to be deposited.
    [1]