Class 10 Science · Chapter 2

Acids, Bases and Salts

208 Class 10 Science questions on Acids, Bases and Salts from the NCERT textbook, NCERT Exemplar and CBSE board papers 2024–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 5 of 11

1. Q81 Exemplar · Long Answer Questions
   A sulphate salt of Group 2 element ​of the Periodic Table is a white, soft substance, which can ​be moulded into different shapes by making ​its ​dough. When this compound is ​left in open for some time, it becomes a solid ​mass and cannot be used for moulding purposes. Identify the sulphate salt and why ​does it show such a behaviour? Give the reaction involved.
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   Plaster of Paris, ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$, absorbs moisture and sets into hard gypsum, ${\text{CaSO}}_4\cdot 2{\text{H}}_2\text{O}$.

   The salt is plaster of Paris, calcium sulphate hemihydrate, ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$ — calcium is a Group 2 element. Left in the open it absorbs moisture from the air and takes up water of crystallisation, changing into gypsum, ${\text{CaSO}}_4\cdot 2{\text{H}}_2\text{O}$, which is a hard solid mass and cannot be moulded. The reaction is ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}+1\frac{1}{2}{\text{H}}_2\text{O}\to {\text{CaSO}}_4\cdot 2{\text{H}}_2\text{O}$. It should therefore be stored in a moisture-proof container.

   Step-by-step solution →
2. Q82 Exemplar · Long Answer Questions
   Identify the compound ​X on the basis of ​the reactions ​given ​below. Also, write the name and chemical ​formulae of ​A, ​B and C.

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   X is sodium hydroxide; A is sodium zincate (${\text{Na}}_2{\text{ZnO}}_2$), B is sodium chloride ($\text{NaCl}$), C is sodium acetate (${\text{CH}}_3\text{COONa}$).

   X is sodium hydroxide, $\text{NaOH}$. A is sodium zincate, ${\text{Na}}_2{\text{ZnO}}_2$, from $\text{Zn}+2\text{NaOH}\to {\text{Na}}_2{\text{ZnO}}_2+{\text{H}}_2$. B is sodium chloride, $\text{NaCl}$, from $\text{NaOH}+\text{HCl}\to \text{NaCl}+{\text{H}}_2\text{O}$. C is sodium acetate, ${\text{CH}}_3\text{COONa}$, from $\text{NaOH}+{\text{CH}}_3\text{COOH}\to {\text{CH}}_3\text{COONa}+{\text{H}}_2\text{O}$.

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3. Q83 CBSE 2026
   Tamarind ​is a ​natural ​source of ​which acid ​?

   1. (a)Acetic acid
   2. (b)Tartaric acid
   3. (c)Oxalic acid
   4. (d)Citric acid
   Show answer

   (b) Tartaric acid

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4. Q84 CBSE 2026
   Tomato is ​a natural ​source ​of ​which ​acid ​?

   1. (a)Acetic acid
   2. (b)Tartaric acid
   3. (c)Oxalic acid
   4. (d)Citric acid
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   (c) Oxalic acid

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5. Q85 CBSE 2026
   Which ​one of the following can be used ​as an acid-base ​indicator ​by a ​visually ​impaired (blind) student ?

   1. (a)Turmeric
   2. (b)Vanilla essence
   3. (c)Methyl orange
   4. (d)Litmus
   Show answer

   (b) Vanilla essence

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6. Q86 CBSE 2026
   A metal carbonate ​reacts with ​a ​solution ​X which forms a ​salt, water and a gas Y. ​What are ​X and Y ​?

   1. (a)X – Sodium hydroxide, Y – Carbon dioxide
   2. (b)X – Sodium hydroxide, Y – Hydrogen
   3. (c)X – Hydrochloric acid, Y – Carbon dioxide
   4. (d)X – Hydrochloric acid, Y – Hydrogen
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   (c) X – Hydrochloric acid, Y – Carbon dioxide

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7. Q87 CBSE 2026
   Rain ​water ​is ​called ​‘acid rain’ ​when ​its ​:

   1. (a)pH falls below 7.2.
   2. (b)pH falls below 14.
   3. (c)pH is above 7.
   4. (d)pH falls below 5.6.
   Show answer

   (d) pH falls below 5.6.

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8. Q88 CBSE 2026
   Which ​of ​the following ​compounds is used ​for removing permanent ​hardness of ​water ​?

   1. (a)Bleaching powder
   2. (b)Washing soda
   3. (c)Baking soda
   4. (d)Caustic soda
   Show answer

   (b) Washing soda

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9. Q89 CBSE 2026
   To a ​small amount of copper oxide in a beaker, when ​we add dilute hydrochloric ​acid slowly ​with stirring, ​the ​change in the colour of the solution is ​due to the formation ​of :

   1. (a)Copper(II) oxide, which is black in colour.
   2. (b)Copper(I) chloride, which is blue in colour.
   3. (c)Copper(II) chloride, which is blue-green in colour.
   4. (d)Copper(I) oxide, which is black in colour.
   Show answer

   (c) Copper(II) chloride, which is blue-green in colour.

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10. Q90 CBSE 2026
    Which of the following ​salts ​do not contain ​water of crystallization ?

    1. (i)​Bleaching ​powder
    2. (ii)​Baking soda
    3. (iii)​Gypsum
    4. (iv)Washing soda

    1. (a)(ii) and (iv)
    2. (b)(i) and (iii)
    3. (c)(ii) and (iii)
    4. (d)(i) and (ii)
    Show answer

    (d) (i) and (ii)

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11. Q91 CBSE 2026
    Which ​of ​the following ​compound is formed when ${\text{CO}}_2$ gas is passed ​through ​ammoniacal brine solution ?

    1. (a)${\text{Na}}_2{\text{CO}}_3$
    2. (b)${\text{NH}}_4\text{Cl}$
    3. (c)$\text{NaOH}$
    4. (d)${\text{NaHCO}}_3$
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    (d) ${\text{NaHCO}}_3$

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12. Q92 CBSE 2026
    Which ​of the following ​compound ​is ​formed when ​electric current ​is passed ​through brine solution ​?

    1. (a)$\text{NaOH}$
    2. (b)$\text{NaCl}$
    3. (c)${\text{NaHCO}}_3$
    4. (d)${\text{Na}}_2{\text{CO}}_3$
    Show answer

    (a) $\text{NaOH}$

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13. Q93 CBSE 2026
    The acid ​present ​in ​tamarind ​is ​:

    1. (a)Oxalic acid
    2. (b)Methanoic acid
    3. (c)Citric acid
    4. (d)Tartaric acid
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    (d) Tartaric acid

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14. Q94 CBSE 2026
    An ​aqueous solution turns red litmus blue. Excess ​addition ​of ​which of the following solution ​would reverse ​the change ?

    1. (a)Sodium hydroxide
    2. (b)Hydrochloric acid
    3. (c)Baking soda
    4. (d)Slaked lime
    Show answer

    (b) Hydrochloric acid

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15. Q95 CBSE 2026
    In the following diagram, ​if ​acetic ​acid of ​same concentration ​is taken ​in place of dilute sulphuric acid, ​then

    1. (a)Same amount of ${\text{H}}_2$ gas will be evolved.
    2. (b)${\text{H}}_2$ gas will not be evolved.
    3. (c)The amount of ${\text{H}}_2$ gas evolved in less amount.
    4. (d)In place of ${\text{H}}_2$ gas, ${\text{O}}_2$ gas will be evolved.
    Show answer

    (c) The amount of ${\text{H}}_2$ gas evolved in less amount.

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16. Q96 CBSE 2026
    The ​acid ​presents in ​nettle sting ​is :

    1. (a)Tartaric acid
    2. (b)Oxalic acid
    3. (c)Methanoic acid
    4. (d)Acetic acid
    Show answer

    (c) Methanoic acid

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17. Q97 CBSE 2026
    Which of ​the ​following ​compounds is ​used as both ​an antacid and ​in a fire extinguisher ?

    1. (a)Sodium hydrogen carbonate
    2. (b)Sodium carbonate
    3. (c)Sodium hydroxide
    4. (d)Sodium chloride
    Show answer

    (a) Sodium hydrogen carbonate

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18. Q98 CBSE 2026
    Study ​the following ​table and select ​the ​correct option :

    Option	Salt	Acid used	Base used	Nature of Salt
    (a)	NaCl	HCl	NaOH	Basic
    (b)	Na₂CO₃	H₂CO₃	NaOH	Neutral
    (c)	Na₂SO₄	H₂SO₄	NaOH	Acidic
    (d)	CH₃COONa	CH₃COOH	NaOH	Basic

    1. (a)Salt: $\text{NaCl}$; Acid used: $\text{HCl}$; Base used: $\text{NaOH}$; Nature of Salt: Basic
    2. (b)Salt: ${\text{Na}}_2{\text{CO}}_3$; Acid used: ${\text{H}}_2{\text{CO}}_3$; Base used: $\text{NaOH}$; Nature of Salt: Neutral
    3. (c)Salt: ${\text{Na}}_2{\text{SO}}_4$; Acid used: ${\text{H}}_2{\text{SO}}_4$; Base used: $\text{NaOH}$; Nature of Salt: Acidic
    4. (d)Salt: ${\text{CH}}_3\text{COONa}$; Acid used: ${\text{CH}}_3\text{COOH}$; Base used: $\text{NaOH}$; Nature of Salt: Basic
    Show answer

    (d) Salt: ${\text{CH}}_3\text{COONa}$; Acid used: ${\text{CH}}_3\text{COOH}$; Base used: $\text{NaOH}$; Nature of Salt: Basic

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19. Q99 CBSE 2026
    During the ​preparation ​of hydrogen chloride ​gas on ​a humid day, ​the gas is usually passed through a guard ​tube containing calcium chloride. The role of ${\text{CaCl}}_2$ taken in guard ​tube is to –

    1. (a)Absorb the evolved gas
    2. (b)Moisten the gas
    3. (c)Absorb moisture from the gas
    4. (d)Absorb chloride ions from the evolved gas
    Show answer

    (c) Absorb moisture from the gas

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20. Q100 CBSE 2026
    The pH of the ​gastric ​juices ​released ​during digestion ​is ​:

    1. (a)Less than $7$
    2. (b)More than $7$
    3. (c)Equal to $7$
    4. (d)Equal to $0$
    Show answer

    (a) Less than $7$

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