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NCERT Exemplar · Class 10 Science Acids, Bases and Salts

48 questions · 48 still being checked

Multiple Choice Questions 21–30 (part 3 of 5)

  1. Exercise 21

    Which of the following is used for dissolution of gold?
    (a)
    Hydrochloric acid
    (b)
    Sulphuric acid
    (c)
    Nitric acid
    (d)
    Aqua regia

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    NCERT’s answer
    (d)
    (d) Aqua regia.A freshly prepared \(\displaystyle 3:1\) mixture of concentrated \(\displaystyle \mathrm{HCl}\) and concentrated \(\displaystyle \mathrm{HNO_3}\) dissolves gold, which resists either acid alone.

  2. Exercise 22

    Which of the following is not a mineral acid?
    (a)
    Hydrochloric acid
    (b)
    Citric acid
    (c)
    Sulphuric acid
    (d)
    Nitric acid

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    NCERT’s answer
    (b)
    (b) Citric acid.Hydrochloric, sulphuric and nitric acids are mineral (inorganic) acids; citric acid is an organic acid found in citrus fruits, not derived from a mineral.

  3. Exercise 23

    Which among the following is not a base?
    (a)
    NaOH
    (b)
    KOH
    (c)
    NH4OH\displaystyle \mathrm{NH}_4 \mathrm{OH}
    (d)
    C2H5OH\displaystyle \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}

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    NCERT’s answer
    (d)
    (d) \(\displaystyle \mathrm{C_2H_5OH}\).NaOH, KOH and \(\displaystyle \mathrm{NH_4OH}\) release \(\displaystyle \mathrm{OH^-}\) and turn litmus blue; ethanol is a neutral alcohol, not a base.

  4. Exercise 24

    Which of the following statements is not correct?
    (a)
    All metal carbonates react with acid to give a salt, water and carbon dioxide
    (b)
    All metal oxides react with water to give salt and acid
    (c)
    Some metals react with acids to give salt and hydrogen
    (d)
    Some non metal oxides react with water to form an acid

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    NCERT’s answer
    (b)
    (b) All metal oxides react with water to give salt and acid.\[\mathrm{CaO + H_2O \rightarrow Ca(OH)_2} \] A metal oxide is basic: water gives a base, not an acid; most metal oxides are also insoluble and never react with water.

  5. Exercise 25

    Match the chemical substances given in Column (A) with their appropriate application given in Column (B)
    Column (A)Column (B)
    (A) Bleaching powder(i) Preparation of glass
    (B) Baking soda(ii) Production of H2\displaystyle \mathrm{H}_2 and Cl2\displaystyle \mathrm{Cl}_2
    (C) Washing soda(iii) Decolourisation
    (D) Sodium chloride(iv) Antacid
    (a)
    A—(ii), B—(i), C—(iv), D—(iii)
    (b)
    A—(iii), B—(ii), C—(iv), D—(i)
    (c)
    A—(iii), B—(iv), C—(i), D—(ii)
    (d)
    A—(ii), B—(iv), C—(i), D—(iii)

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    NCERT’s answer
    (c)
    (c) A—(iii), B—(iv), C—(i), D—(ii). Bleaching powder decolourises; baking soda is an antacid; washing soda enters glass-making; \(\displaystyle \mathrm{NaCl}\) electrolysis (chloralkali) gives \(\displaystyle \mathrm{H_2}\) and \(\displaystyle \mathrm{Cl_2}\).\[2\mathrm{NaCl(aq)} + 2\mathrm{H_2O(l)} \xrightarrow{\text{electrolysis}} 2\mathrm{NaOH(aq)} + \mathrm{Cl_2(g)} + \mathrm{H_2(g)} \]

  6. Exercise 26

    Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained? (You may use colour guide given in Figure 2.2\displaystyle 2.2
    (a)
    Red
    (b)
    Yellow
    (c)
    Yellowish green
    (d)
    Blue
    NCERT_Question_Class10_Science_Exemplar_Ch2_Q26

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    NCERT’s answer
    (c)
    (c) Yellowish green. Equal volumes, equal concentration — equal moles of strong acid and strong base neutralise completely:\[\mathrm{HCl(aq)} + \mathrm{NaOH(aq)} \rightarrow \mathrm{NaCl(aq)} + \mathrm{H_2O(l)} \]The resulting salt solution is neutral, \(\displaystyle \mathrm{pH} = 7\), the yellowish-green band on the pH chart of Figure 2.2.

  7. Exercise 27

    Which of the following is(are) true when HCl (g) is passed through water?
    (i)
    It does not ionise in the solution as it is a covalent compound.
    (ii)
    It ionises in the solution
    (iii)
    It gives both hydrogen and hydroxyl ion in the solution
    (iv)
    It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule
    (a) (i) only
    (b) (iii) only
    (c) (ii) and (iv)
    (d) (iii) and (iv)

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    NCERT’s answer
    (c)
    Hint— Though HCl gas is a covalent compound, in the aqueous solution it ionizes to form \(\displaystyle \mathrm{H}^{+}(\mathrm{aq})\) and \(\displaystyle \mathrm{Cl}^{-}(\mathrm{aq})\) ions.
    (c) (ii) and (iv). \(\displaystyle \mathrm{HCl}\) is covalent but ionises fully once in water, its \(\displaystyle \mathrm{H^+}\) combining with a water molecule:\[\mathrm{HCl(g)} + \mathrm{H_2O(l)} \rightarrow \mathrm{H_3O^+(aq)} + \mathrm{Cl^-(aq)} \]No \(\displaystyle \mathrm{OH^-}\) forms, so (i) and (iii) are false.

  8. Exercise 28

    Which of the following statements is true for acids?
    (a)
    Bitter and change red litmus to blue
    (b)
    Sour and change red litmus to blue
    (c)
    Sour and change blue litmus to red
    (d)
    Bitter and change blue litmus to red

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    NCERT’s answer
    (c)
    (c) Sour and change blue litmus to red. Acids taste sour and turn blue litmus paper red; the reverse pairing (bitter, red→blue) instead describes bases.

  9. Exercise 29

    Which of the following are present in a dilute aqueous solution of hydrochloric acid?
    (a)
    H3O++Cl−\displaystyle \mathrm{H}_3 \mathrm{O}^{+}+\mathrm{Cl}^{-}
    (b)
    H3O++OH−\displaystyle \mathrm{H}_3 \mathrm{O}^{+}+\mathrm{OH}^{-}
    (c)
    Cl−+OH−\displaystyle \mathrm{Cl}^{-}+\mathrm{OH}^{-}
    (d)
    unionised HCl

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    NCERT’s answer
    (a)
    (a) \(\displaystyle \mathrm{H_3O^+} + \mathrm{Cl^-}\). Dilute \(\displaystyle \mathrm{HCl}\) is a strong acid and ionises almost completely in water:\[\mathrm{HCl(aq)} + \mathrm{H_2O(l)} \rightarrow \mathrm{H_3O^+(aq)} + \mathrm{Cl^-(aq)} \]No \(\displaystyle \mathrm{OH^-}\) and negligible unionised \(\displaystyle \mathrm{HCl}\) remain.

  10. Exercise 30

    Identify the correct representation of reaction occurring during chloralkali process
    (a)
    2NaCl(l)+2H2O(l)→2NaOH(l)+Cl2( g)+H2( g)\displaystyle 2 \mathrm{NaCl}(\mathrm{l})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{l})+\mathrm{Cl}_2(\mathrm{~g})+\mathrm{H}_2(\mathrm{~g})
    (b)
    2NaCl(aq)+2H2O(aq)→2NaOH(aq)+Cl2( g)+H2( g)\displaystyle 2 \mathrm{NaCl}(\mathrm{aq})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{aq}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{Cl}_2(\mathrm{~g})+\mathrm{H}_2(\mathrm{~g})
    (c)
    2NaCl(aq)+2H2O(l)→2NaOH(aq)+Cl2(aq)+H2(aq)\displaystyle 2 \mathrm{NaCl}(\mathrm{aq})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{Cl}_2(\mathrm{aq})+\mathrm{H}_2(\mathrm{aq})
    (d)
    2NaCl(aq)+2H2O(l)→2NaOH(aq)+Cl2( g)+H2( g)\displaystyle 2 \mathrm{NaCl}(\mathrm{aq})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{Cl}_2(\mathrm{~g})+\mathrm{H}_2(\mathrm{~g})

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    NCERT’s answer
    (d)
    (d)\[2\mathrm{NaCl(aq)} + 2\mathrm{H_2O(l)} \rightarrow 2\mathrm{NaOH(aq)} + \mathrm{Cl_2(g)} + \mathrm{H_2(g)} \]Brine is \(\displaystyle \mathrm{NaCl}\) in liquid water; \(\displaystyle \mathrm{NaOH}\) stays in solution (aq); \(\displaystyle \mathrm{Cl_2}\) and \(\displaystyle \mathrm{H_2}\) bubble off as gases (g).