PYQ Vault

Day 47: CBSE Class 10 Science

5 questions. Try each one first, then open its answer.

  1. Question 1

    Acids, Bases and Salts. This type asked 3 times: 2023, 2025, 2026. This one: 2026

    27 (a)
    Give reasons : (i) For dilution of an acid, acid is added into water and not water into acid. (ii) Dry HCl\mathrm{HCl} gas does not turn blue litmus red whereas dilute hydrochloric acid does. (iii) Blue colour of Copper(II) sulphate crystals turns white on heating.

  2. Question 2

    Acids, Bases and Salts. This type asked 3 times: 2023, 2024, 2026. This one: 2026

    25
    (a) A compound ‘A’ is used in soda-lime fire-extinguisher and decomposes on heating to form compound ‘B’. Compound ‘B’ is used for removing permanent hardness of water. Identify ‘A’ and ‘B’. (b) Write chemical formula of Plaster of Paris. At what temperature gypsum is heated to obtain Plaster of Paris ?

  3. Question 3

    Acids, Bases and Salts. This type asked 3 times: 2023, 2025, 2026. This one: 2026

    23
    Which one of the following chemicals is used in soda-acid fire-extinguishers ?

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  4. Question 4

    Acids, Bases and Salts. This type asked 3 times: 2024, 2025, 2026. This one: 2026

    19
    An aqueous solution turns red litmus blue. Excess addition of which of the following solution would reverse the change ?

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  5. Question 5

    Acids, Bases and Salts. This type asked 3 times: 2023, 2024, 2026. This one: 2026

    21
    The pH of the gastric juices released during digestion is :

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