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NCERT Exemplar · Class 10 Science Carbon and its Compounds

57 questions · 57 still being checked

Multiple Choice Questions 1–10 (part 1 of 6)

  1. Exercise 1

    Carbon exists in the atmosphere in the form of
    (a)
    carbon monoxide only
    (b)
    carbon monoxide in traces and carbon dioxide
    (c)
    carbon dioxide only
    (d)
    coal

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    NCERT’s answer
    (b)
    (b) Carbon monoxide in traces and carbon dioxide. Carbon dioxide is a steady atmospheric constituent; carbon monoxide appears only in traces, from incomplete combustion of fuels.

  2. Exercise 2

    Which of the following statements are usually correct for carbon compounds? These
    (i)
    are good conductors of electricity
    (ii)
    are poor conductors of electricity
    (iii)
    have strong forces of attraction between their molecules
    (iv)
    do not have strong forces of attraction between their molecules
    (a) (i) and (iii)
    (b) (ii) and (iii)
    (c) (i) and (iv)
    (d) (ii) and (iv)

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    NCERT’s answer
    (d)
    (d) (ii) and (iv). Carbon compounds are covalent, so no free ions or electrons carry charge -- poor conductors. Weak van der Waals forces between molecules give low melting and boiling points.

  3. Exercise 3

    A molecule of ammonia (NH3)\displaystyle \left(\mathrm{NH}_3\right) has
    (a)
    only single bonds
    (b)
    only double bonds
    (c)
    only triple bonds
    (d)
    two double bonds and one single bond

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    NCERT’s answer
    (a)
    (a) Only single bonds. Nitrogen shares one electron pair with each of three hydrogen atoms, completing its octet with a lone pair left over.

  4. Exercise 4

    Buckminsterfullerene is an allotropic form of
    (a)
    phosphorus
    (b)
    sulphur
    (c)
    carbon
    (d)
    tin

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    NCERT’s answer
    (c)
    (c) Carbon. Buckminsterfullerene is \(\displaystyle \mathrm{C_{60}}\), a cage of $\displaystyle 60$ carbon atoms.

  5. Exercise 5

    Which of the following are correct structural isomers of butane?
    (i)
    (ii)
    (iii)
    (iv)
    (a) (i) and (iii)
    (b) (ii) and (iv)
    (c) (i) and (ii)
    (d) (iii) and (iv)
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q5
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q5_2
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q5_3
    NCERT_Question_Class10_Science_Exemplar_Ch4_Q5_4

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    NCERT’s answer
    (c)
    (c) (i) and (ii): both \(\displaystyle \mathrm{C_4H_{10}}\) -- (i) a straight chain, (ii) a three-carbon chain with a \(\displaystyle \mathrm{CH_3}\) branch. (iii) and (iv) are rings, \(\displaystyle \mathrm{C_4H_8}\), so not isomers of butane.

  6. Exercise 6

    CH3−CH2−OH→ Alkaline KMnO4+ Heat CH3−COOH\displaystyle \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{OH} \xrightarrow{\text { Alkaline } \mathrm{KMnO}_4+\text { Heat }} \mathrm{CH}_3-\mathrm{COOH}
    In the above given reaction, alkaline KMnO4\displaystyle \mathrm{KMnO}_4 acts as
    (a)
    reducing agent
    (b)
    oxidising agent
    (c)
    catalyst
    (d)
    dehydrating agent

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    NCERT’s answer
    (b)
    (b) Oxidising agent. Alkaline \(\displaystyle \mathrm{KMnO_4}\) adds oxygen to the alcohol, raising the carbon's oxidation state -- gain of oxygen is oxidation: \[\mathrm{CH_3-CH_2-OH} + 2[\mathrm{O}] \xrightarrow{\text{Alkaline } \mathrm{KMnO_4},\ \Delta} \mathrm{CH_3-COOH} + \mathrm{H_2O} \] So \(\displaystyle \mathrm{KMnO_4}\) is the oxidising agent.

  7. Exercise 7

    Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of
    (a)
    Addition reaction
    (b)
    Substitution reaction
    (c)
    Displacement reaction
    (d)
    Oxidation reaction

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    NCERT’s answer
    (a)
    (a) Addition reaction. Hydrogen adds across the oil's \(\displaystyle \mathrm{C=C}\) double bond; Ni or Pd only speeds the addition, it is not consumed: \[\mathrm{R-CH=CH-R'} + \mathrm{H_2} \xrightarrow{\text{Ni or Pd}} \mathrm{R-CH_2-CH_2-R'} \] Unsaturated oil becomes saturated fat.

  8. Exercise 8

    In which of the following compounds, — OH is the functional group?
    (a)
    Butanone
    (b)
    Butanol
    (c)
    Butanoic acid
    (d)
    Butanal

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    NCERT’s answer
    (b)
    (b) Butanol. The suffix '-ol' marks the alcohol group, \(\displaystyle \mathrm{-OH}\); butanone carries \(\displaystyle \mathrm{>C=O}\), butanoic acid carries \(\displaystyle \mathrm{-COOH}\), and butanal carries \(\displaystyle \mathrm{-CHO}\).

  9. Exercise 9

    The soap molecule has a
    (a)
    hydrophilic head and a hydrophobic tail
    (b)
    hydrophobic head and a hydrophilic tail
    (c)
    hydrophobic head and a hydrophobic tail
    (d)
    hydrophilic head and a hydrophilic tail

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    NCERT’s answer
    (a)
    (a) The ionic \(\displaystyle \mathrm{-COO^-Na^+}\) end is polar and water-loving (hydrophilic head); the long hydrocarbon chain is non-polar and water-repelling (hydrophobic tail).

  10. Exercise 10

    Which of the following is the correct representation of electron dot structure of nitrogen?
    (a)
    :N¨:N¨:\displaystyle :\ddot{\mathrm{N}}:\ddot{\mathrm{N}}:
    (b)
    :N˙::N˙:\displaystyle :\dot{\mathrm{N}}::\dot{\mathrm{N}}:
    (c)
    :N¨⋮N˙:\displaystyle :\ddot{\mathrm{N}}\vdots\dot{\mathrm{N}}:
    (d)
    :N⋮⋮N:\displaystyle :\mathrm{N}\vdots\vdots\mathrm{N}:

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    NCERT’s answer
    (d)
    (d) Each N has $\displaystyle 5$ valence electrons; sharing $\displaystyle 3$ pairs (a triple bond) plus keeping $\displaystyle 1$ lone pair completes the octet on both atoms. \[\text{bond} = 3\ \text{shared pairs}\ (6e^-),\quad \text{lone pair} = 1\ \text{per N}\ (2e^-\ \text{each}) \] \[\text{electrons around each N} = 6 + 2 = 8\ (\text{octet complete}) \]