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NCERT Exemplar · Class 10 Science Carbon and its Compounds

57 questions · 57 still being checked

Multiple Choice Questions 11–20 (part 2 of 6)

  1. Exercise 11

    Structural formula of ethyne is
    (a)
    H−C≡C−H\displaystyle \mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}
    (b)
    H3−C≡C−H\displaystyle \mathrm{H}_3-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}
    (c)
    (d)
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q11
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q11_2

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    NCERT’s answer
    (a)
    (a) Ethyne, \(\displaystyle \mathrm{C_2H_2}\), is an alkyne: a carbon-carbon triple bond with one H on each carbon. (c) is ethene (C=C) and (d) is ethane (C-C), each with more H atoms than ethyne.

  2. Exercise 12

    Identify the unsaturated compounds from the following
    (i)
    Propane
    (ii)
    Propene
    (iii)
    Propyne
    (iv)
    Chloropropane
    (a) (i) and (ii)
    (b) (ii) and (iv)
    (c) (iii) and (iv)
    (d) (ii) and (iii)

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    NCERT’s answer
    (d)
    (d) Propene (\(\displaystyle \mathrm{C_3H_6}\), C=C) and propyne (\(\displaystyle \mathrm{C_3H_4}\), C\(\displaystyle \equiv\)C) carry a multiple bond, the mark of unsaturation; propane and chloropropane have only single C-C and C-H bonds.

  3. Exercise 13

    Chlorine reacts with saturated hydrocarbons at room temperature in the
    (a)
    absence of sunlight
    (b)
    presence of sunlight
    (c)
    presence of water
    (d)
    presence of hydrochloric acid

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    NCERT’s answer
    (b)
    (b) Saturated hydrocarbons are inert at room temperature; sunlight supplies the energy to split \(\displaystyle \mathrm{Cl_2}\) into reactive chlorine radicals, which then substitute an H. \[\mathrm{CH_4 + Cl_2 \xrightarrow{\text{sunlight}} CH_3Cl + HCl} \]

  4. Exercise 14

    In the soap micelles
    (a)
    the ionic end of soap is on the surface of the cluster while the carbon chain is in the interior of the cluster.
    (b)
    ionic end of soap is in the interior of the cluster and the carbon chain is out of the cluster.
    (c)
    both ionic end and carbon chain are in the interior of the cluster
    (d)
    both ionic end and carbon chain are on the exterior of the cluster

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    NCERT’s answer
    (a)
    (a) In water, the charged head of each soap molecule faces outward while hydrophobic hydrocarbon tails cluster inward, away from water; this traps grease at the centre.

  5. Exercise 15

    Pentane has the molecular formula C5H12\displaystyle \mathrm{C}_5 \mathrm{H}_{12}. It has
    (a)
    5\displaystyle 5 covalent bonds
    (b)
    12\displaystyle 12 covalent bonds
    (c)
    16\displaystyle 16 covalent bonds
    (d)
    17\displaystyle 17 covalent bonds

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    NCERT’s answer
    (c)
    (c) Pentane's chain has $\displaystyle 4$ C-C bonds and $\displaystyle 12$ C-H bonds (one per H atom). \[(n-1)\ \text{C-C bonds} + (2n+2)\ \text{C-H bonds},\quad n = 5 \] \[(5-1) + (2 \times 5 + 2) = 4 + 12 = 16\ \text{covalent bonds} \]

  6. Exercise 16

    Structural formula of benzene is
    (a)
    (b)
    (c)
    (d)
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q16
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q16_2
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q16_3
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q16_4

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    NCERT’s answer
    (c)
    (c) Benzene, \(\displaystyle \mathrm{C_6H_6}\), is a hexagonal ring of six CH units with alternating single and double C-C bonds (Kekulé structure); each carbon thus completes four bonds.

  7. Exercise 17

    Ethanol reacts with sodium and forms two products. These are
    (a)
    sodium ethanoate and hydrogen
    (b)
    sodium ethanoate and oxygen
    (c)
    sodium ethoxide and hydrogen
    (d)
    sodium ethoxide and oxygen

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    NCERT’s answer
    (c)
    (c) Sodium ethoxide and hydrogen. \[2\,\mathrm{C_2H_5OH} + 2\,\mathrm{Na} \rightarrow 2\,\mathrm{C_2H_5ONa} + \mathrm{H_2}\uparrow \] Sodium displaces the H of the \(\displaystyle \mathrm{-OH}\) group and releases \(\displaystyle \mathrm{H_2}\) gas.

  8. Exercise 18

    The correct structural formula of butanoic acid is
    (a)
    (b)
    (c)
    (d)
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q18
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q18_2
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q18_3
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q18_4

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    NCERT’s answer
    (d)
    (d) \(\displaystyle \mathrm{H_3C-CH_2-CH_2-COOH}\), butanoic acid. Saturated, unbranched, four carbons ending in \(\displaystyle \mathrm{-COOH}\); (a) has a \(\displaystyle \mathrm{C=C}\) bond (an unsaturated acid), (b) has five carbons, (c) ends in \(\displaystyle \mathrm{-OH}\) only, with no carbonyl.

  9. Exercise 19

    Vinegar is a solution of
    (a)
    50\displaystyle 50% – 60\displaystyle 60% acetic acid in alcohol
    (b)
    5\displaystyle 5% – 8\displaystyle 8% acetic acid in alcohol
    (c)
    5\displaystyle 5% – 8\displaystyle 8% acetic acid in water
    (d)
    50\displaystyle 50% – 60\displaystyle 60% acetic acid in water

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    NCERT’s answer
    (c)
    (c) $\displaystyle 5$%–$\displaystyle 8$% acetic acid in water. Vinegar is dilute ethanoic acid in water, not in alcohol and not $\displaystyle 50$%–$\displaystyle 60$%.

  10. Exercise 20

    Mineral acids are stronger acids than carboxylic acids because
    (i)
    mineral acids are completely ionised
    (ii)
    carboxylic acids are completely ionised
    (iii)
    mineral acids are partially ionised
    (iv)
    carboxylic acids are partially ionised
    (a) (i) and (iv)
    (b) (ii) and (iii)
    (c) (i) and (ii)
    (d) (iii) and (iv)

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    NCERT’s answer
    (a)
    (a) (i) and (iv). \[\mathrm{HCl} \rightarrow \mathrm{H^+} + \mathrm{Cl^-} \quad \text{(complete)} \] \[\mathrm{CH_3COOH} \rightleftharpoons \mathrm{CH_3COO^-} + \mathrm{H^+} \quad \text{(partial, equilibrium)} \] Mineral acids dissociate fully; carboxylic acids are weak and only partly ionise, so they release fewer \(\displaystyle \mathrm{H^+}\) and are the weaker acid.