PYQ Vault

Day 86: CBSE Class 10 Science

5 questions (11 parts). Try each one first, then open its answer.

  1. Question 1

    Carbon and its Compounds. Asked once: 2025 (same type asked 3 times)

    34 (b)
    (i) A carbon compound X is a good solvent. On reaction with sodium, X forms two products Y and Z. Z is used to convert vegetable oil into vegetable ghee. Identify and name X, Y and Z. Also write the equation of reaction of X with sodium to justify your answer. (ii) Write chemical equation to show what happens when ethanol : (I) burns in oxygen/air. (II) is heated at 443 K in excess conc. H2SO4\mathrm{H_2SO_4}. (III) reacts with acidified potassium dichromate.

  2. Question 2

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

    20
    The hydrocarbons with general formula CnH2n\mathrm{C_nH_{2n}} represents :

    Tap an option to check your answer.

  3. Question 3

    Carbon and its Compounds. Asked once: 2025 (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.
    17
    Assertion (A) : Propanal and propanone are structural isomers. Reason (R) : Propanal and propanone both have the same molecular formula.

    Tap an option to check your answer.

  4. Question 4 (case study, 4 parts)

    Carbon and its Compounds. Asked once: 2025 (same type asked 3 times)

    ‘A’ and ‘B’ are two salts used for washing purposes. Salt ‘A’ is used for bathing also. Four test tubes I, II, III and IV as mentioned below are taken. I. Rain water + solution of salt ‘A’ II. Rain water + solution of salt ‘B’ III. Tubewell water + solution of salt ‘A’ IV. Tubewell water + solution of salt ‘B’ The test tubes are shaken one by one almost identically for the same time and the lengths of foam formed in each test tube is noted.
    37 (a)
    In which one of the four test tubes is the foam formed the minimum ?
    37 (b)
    Differentiate between salt A and salt B.
    37 (c) (i)
    What are esters ? What happens when an ester reacts with an alkali (say sodium hydroxide) ? Give chemical equation for the reaction.
    37 (c) (ii)
    What is the cause of hardness of water ? Sometimes it is observed that while bathing foam is formed with difficulty and an insoluble substance is formed. Name this substance and write the cause of its formation.

  5. Question 5 (case study, 4 parts)

    Carbon and its Compounds. Asked once: 2025 (same type asked 3 times)

    The combining capacity of various elements depends on the number of valence electrons. Also the reactivity of elements is explained as their tendency to attain a completely filled outer shell, that is, to attain a noble gas configuration. This may be either through gain of electrons or loss of electrons or sharing of electrons.
    37 (a)
    An element A has atomic number 16, how will it attain its nearest noble gas configuration ?
    37 (b)
    Write the number of (i) single and (ii) double covalent bonds in a molecule of butene (C4H8)(\mathrm{C_4H_8}).
    37 (c) (i)
    Explain the formation of a molecule of ammonia (NH3)(\mathrm{NH_3}), using electron dot structure. (Atomic number of nitrogen is 7)
    37 (c) (ii)
    Why does carbon share its valence electrons with other atoms of carbon or with atoms of other elements ?