Class 10 Science · Chapter 2

Acids, Bases and Salts

352 Class 10 Science questions on Acids, Bases and Salts from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 6 of 18

1. Q101 CBSE 2026
   ‘Phenolphthalein’ is an ​example ​of ​:

   1. (a)Natural indicator
   2. (b)Synthetic indicator
   3. (c)Olfactory indicator
   4. (d)Universal indicator
   Show answer

   (b) Synthetic indicator

   Step-by-step solution →
2. Q102 CBSE 2026
   The natural sources ​of ​oxalic acid, lactic ​acid ​and methanoic ​acid respectively are ​:

   1. (a)tomato, curd, ant-sting
   2. (b)tomato, orange, nettle-sting
   3. (c)orange, milk, ant-sting
   4. (d)orange, sour milk, nettle-sting
   Show answer

   (a) tomato, curd, ant-sting

   Step-by-step solution →
3. Q103 CBSE 2026
   Baking powder is a mixture of :

   1. (a)Sodium carbonate + Acetic acid
   2. (b)Sodium carbonate + Tartaric acid
   3. (c)Sodium hydrogen carbonate + Tartaric acid
   4. (d)Sodium hydrogen carbonate + Acetic acid
   Show answer

   (c) Sodium hydrogen carbonate + Tartaric acid

   Step-by-step solution →
4. Q104 CBSE 2026
   In which ​case/cases will ​the bulb ​glow ​considering ​that all other ​connections of electric circuit are complete and working ?

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

   (d) Case (iii) only

   Step-by-step solution →
5. Q105 CBSE 2026
   Four solutions, namely fructose, ethanol, hydrochloric acid and sodium hydroxide filled in four separate beakers are connected one by ​one ​in an electric circuit with a bulb. The solutions in ​which the ​bulb will glow when current is ​passed are ​:

   1. (a)ethanol and hydrochloric acid
   2. (b)fructose and ethanol
   3. (c)fructose and sodium hydroxide
   4. (d)hydrochloric acid and sodium hydroxide
   Show answer

   (d) hydrochloric acid and sodium hydroxide

   Step-by-step solution →
6. Q106 CBSE 2026
   Which of ​the ​following ​statements is true ​for acids ​?

   1. (a)Bitter and change red litmus to blue.
   2. (b)Sour and change red litmus to blue.
   3. (c)Sour and change blue litmus to red.
   4. (d)Bitter and change blue litmus to red.
   Show answer

   (c) Sour and change blue litmus to red.

   Step-by-step solution →
7. Q107 CBSE 2026
   Which of the ​following aqueous solution reacts ​with ​crushed egg-shells to ​give a ​gas ​that turns lime water milky ?

   1. (a)$\text{KCl}$
   2. (b)$\text{HCl}$
   3. (c)$\text{NaCl}$
   4. (d)${\text{NH}}_4\text{Cl}$
   Show answer

   (b) $\text{HCl}$

   Step-by-step solution →
8. Q108 CBSE 2026
   How ​will you ​protect ​yourself from the ​heat generated ​while ​diluting ​a concentrated acid ​?

   1. (a)By adding acid to water with constant stirring.
   2. (b)By adding water to acid with constant stirring.
   3. (c)By adding water to acid followed by base.
   4. (d)By adding base to acid with constant stirring.
   Show answer

   (a) By adding acid to water with constant stirring.

   Step-by-step solution →
9. Q109 CBSE 2026
   Which one ​of the following ​chemicals ​is used ​in soda-acid fire-extinguishers ​?

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

   (b) Sodium hydrogen carbonate

   Step-by-step solution →
10. Q110 CBSE 2026
    When zinc ​reacts ​with $\text{NaOH}$, ​the product ​formed is ​:

    1. (a)${\text{Na}}_2\text{O}$
    2. (b)$\text{ZnO}$
    3. (c)${\text{Na}}_2{\text{ZnO}}_2$
    4. (d)${\text{Zn(OH)}}_2$
    Show answer

    (c) ${\text{Na}}_2{\text{ZnO}}_2$

    Step-by-step solution →
11. Q111 CBSE 2026
    Turmeric is an example of :

    1. (a)Natural indicator
    2. (b)Synthetic indicator
    3. (c)Olfactory indicator
    4. (d)Universal indicator
    Show answer

    (a) Natural indicator

    Step-by-step solution →
12. Q112 CBSE 2026
    Which of ​the ​following acid-base indicators will be ​used ​by ​a visually challenged student ​to detect ​the presence of acid in ​a given solution ?

    1. (a)Blue litmus
    2. (b)Clove oil
    3. (c)Red cabbage extract
    4. (d)Methyl orange
    Show answer

    (b) Clove oil

    Step-by-step solution →
13. Q113 CBSE 2026
    Which ​of the ​following solution will ​not ​conduct ​electricity ​?

    1. (a)Hydrochloric acid
    2. (b)Sodium hydroxide
    3. (c)Sulphuric acid
    4. (d)Glucose
    Show answer

    (d) Glucose

    Step-by-step solution →
14. Q114 CBSE 2026
    For question number 24, two statements are given-one labelled ​as Assertion (A) and the other labelled as ​Reason (R). Answer ​this question selecting the appropriate ​option from (a), (b), ​(c) and ​(d) given below :

    Assertion (A): Sodium acetate is a basic salt.

    Reason (R): It is because it is a salt of weak acid and strong base.

    1. (a)Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).

    Step-by-step solution →
15. Q115 CBSE 2026
    For ​Question ​number 24, two statements ​are given ​— one labelled as Assertion (A) and the ​other labelled as Reason (R). Select the correct answer to this question from ​the codes ​(a), ​(b), (c) and (d) as given below.

    Assertion (A): It is advised that while diluting a concentrated acid, acid should be added slowly to water and not water to acid.

    Reason (R): The process of dissolving an acid in water is endothermic.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (c) Assertion (A) is true, but Reason (R) is false.

    Step-by-step solution →
16. Q116 CBSE 2026
    1. (a)A compound ‘A’ is used ​in soda-lime ​fire-extinguisher and decomposes ​on heating to form compound ‘B’. Compound ‘B’ is used for removing permanent hardness of ​water. Identify ‘A’ and ‘B’.
    2. (b)Write chemical formula of Plaster of ​Paris. At what temperature gypsum is ​heated to obtain Plaster of Paris ​?
    Show answer

    A is sodium hydrogencarbonate, B is sodium carbonate; Plaster of Paris is ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$, made by heating gypsum to 373 K.

    (a) ‘A’ is sodium hydrogencarbonate (baking soda), ${\text{NaHCO}}_3$, and ‘B’ is sodium carbonate (washing soda), ${\text{Na}}_2{\text{CO}}_3$, formed by $2{\text{NaHCO}}_3\stackrel{\Delta }{\to }{\text{Na}}_2{\text{CO}}_3+{\text{H}}_2\text{O}+{\text{CO}}_2$. (b) Plaster of Paris is calcium sulphate hemihydrate, ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$. Gypsum is heated to $373$ K ($100{}^{\circ }\text{C}$) to obtain it.

    Step-by-step solution →
17. Q117 CBSE 2026
    Write ​the balanced chemical ​equations ​involved ​in ​the preparation of

    1. (a)​Bleaching powder
    2. (b)Baking ​soda
    Show answer

    Chlorine on dry slaked lime gives bleaching powder; carbon dioxide in ammonia-saturated brine gives baking soda.

    (a) Bleaching powder is prepared by the action of chlorine on dry slaked lime: ${\text{Ca(OH)}}_2(s)+{\text{Cl}}_2(g)⟶{\text{CaOCl}}_2(s)+{\text{H}}_2\text{O}(l)$ It may also be written $2{\text{Ca(OH)}}_2+2{\text{Cl}}_2⟶{\text{Ca(ClO)}}_2+{\text{CaCl}}_2+2{\text{H}}_2\text{O}$. (b) Baking soda, sodium hydrogencarbonate, is prepared from brine by the ammonia-soda process, also called the Solvay process. Carbon dioxide is passed into brine saturated with ammonia: $\text{NaCl}(aq)+{\text{H}}_2\text{O}(l)+{\text{CO}}_2(g)+{\text{NH}}_3(g)⟶{\text{NH}}_4\text{Cl}(aq)+{\text{NaHCO}}_3(s)$ Both equations are balanced as written.

    Step-by-step solution →
18. Q118 CBSE 2026
    Write ​the ​balanced chemical equation for the preparation ​of :

    1. (a)Sodium hydroxide by ​electrolysis ​of brine ​solution
    2. (b)Sodium ​carbonate
    Show answer

    Electrolysis of brine gives $\text{NaOH}$, ${\text{Cl}}_2$ and ${\text{H}}_2$; heating ${\text{NaHCO}}_3$ gives ${\text{Na}}_2{\text{CO}}_3$.

    (a) Sodium hydroxide is prepared by the chlor-alkali process, the electrolysis of concentrated brine: $2\text{NaCl(aq)}+2{\text{H}}_2\text{O(l)}\stackrel{\text{electrolysis}}{\to }2\text{NaOH(aq)}+{\text{Cl}}_2\text{(g)}+{\text{H}}_2\text{(g)}$. Chlorine is liberated at the anode, hydrogen at the cathode, and the sodium hydroxide is left in the solution near the cathode. (b) Sodium carbonate is prepared by heating sodium hydrogen carbonate, which the Solvay (ammonia-soda) process itself makes from brine: $2{\text{NaHCO}}_3\text{(s)}\stackrel{\Delta }{\to }{\text{Na}}_2{\text{CO}}_3\text{(s)}+{\text{H}}_2\text{O(g)}+{\text{CO}}_2\text{(g)}$, the hydrogen carbonate coming from $\text{NaCl(aq)}+{\text{NH}}_3\text{(g)}+{\text{CO}}_2\text{(g)}+{\text{H}}_2\text{O(l)}⟶{\text{NaHCO}}_3\text{(s)}+{\text{NH}}_4\text{Cl(aq)}$.

    Step-by-step solution →
19. Q119 CBSE 2026
    How is tooth decay ​related ​to ​pH ​? How ​can it ​be prevented ​?
    Show answer

    Decay starts when the mouth's pH falls below 5.5 and acids corrode the enamel; cleaning the mouth and using basic toothpaste prevent it.

    Tooth decay starts when the pH in the mouth falls below 5.5. Bacteria in the mouth break down the sugar and food particles left after eating and produce acids. Below pH 5.5 these acids corrode the tooth enamel (calcium hydroxyapatite, a form of calcium phosphate), even though enamel does not dissolve in water. Prevention: clean the mouth after eating (brush and rinse) so that no food is left for the bacteria, and use toothpaste, which is basic and neutralises the excess acid. Eating fewer sugary foods also helps.

    Step-by-step solution →
20. Q120 CBSE 2026
    Why does one feels ​pain and irritation ​when stung ​by honey-bee ​? Rubbing of baking soda on ​the stung ​area gives ​relief. How ?
    Show answer

    The sting leaves methanoic acid, which causes the pain; baking soda, a mild base, neutralises the acid and gives relief.

    When a honey-bee stings, it leaves an acid (methanoic acid, $\text{HCOOH}$) in the skin, and this acid causes the pain and irritation. Baking soda (sodium hydrogencarbonate, ${\text{NaHCO}}_3$) is a mild base, so rubbing it on the stung area neutralises the acid and gives relief: $\text{HCOOH}+{\text{NaHCO}}_3⟶\text{HCOONa}+{\text{H}}_2\text{O}+{\text{CO}}_2$

    Step-by-step solution →