PYQ Vault

Day 85: CBSE Class 10 Science

5 questions (8 parts). Try each one first, then open its answer.

  1. Question 1

    Acids, Bases and Salts. Asked once: 2025 (same type asked 3 times)

    28
    Two substances ‘A’ and ‘B’ are burnt in air separately. For ‘A’, ashes are collected and dissolved in water to get solution ‘X’, while for ‘B’, fumes produced are passed through water to get solution ‘Y’. Both the solutions ‘X’ and ‘Y’ are then tested with pH paper. (a) If ‘X’ gives light blue colour and ‘Y’ gives orange colour to the pH paper, then write the nature and range of pH of ‘X’ and ‘Y’. (b) Which one of the two – A and B, is a metal ? Justify your answer.

  2. Question 2 (case study, 4 parts)

    Acids, Bases and Salts. Asked once: 2025 (same type asked 3 times)

    Acid-base indicators can be used to distinguish between an acid and a base. Universal indicator, a mixture of several indicators, shows different colours at different concentrations of acids and bases, thereby indicating their pH on the pH scale of 0 – 14. The pH of a solution is measured by pH paper, which is a paper impregnated with a universal indicator.
    37 (a)
    Solution P is a strong acid while solution Q is a strong base. On the pH scale, where would you place the solutions P and Q ?
    37 (b)
    A solution has a pH of 7. Name a compound you would use to (i) increase its pH, and (ii) decrease its pH.
    37 (c) (i)
    When the pH of a solution is decreased from 4 to 2, what effect does it produce on its hydronium ion concentration ? State the colour change shown by the pH paper.
    37 (c) (ii)
    A person is feeling pain and irritation in the stomach due to indigestion. What could be the pH of the fluid in the stomach ? Write the common name of the medicines people use for remedy. Give the chemical name of “milk of magnesia” often used for this purpose.

  3. Question 3

    Acids, Bases and Salts. Asked once: 2024 (same type asked 3 times)

    21 (b)
    Some metals react with acids to produce salt and hydrogen gas. Illustrate it with an example. How will you test the presence of this gas ?

  4. Question 4

    Acids, Bases and Salts. Asked once: 2025 (same type asked 3 times)

    28 (b)
    Write chemical equations to show what happens when an acid reacts with a (i) metal (ii) base and (iii) carbonate Write the name of the main product formed in each case.

  5. Question 5

    Carbon and its Compounds. Asked once: 2026 (same type asked 3 times)

    Two statements are given, one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the options given below.
    24
    Assertion (A) : Carbon shows the property of catenation. Reason (R) : C – C bond is weak due to its small size.

    Tap an option to check your answer.