Master Acids Bases And Salts 2 Marks Questions Answers For 2026 Boards Class 10, New Pattern!

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CBSE has changed the pattern of class 10 science exam from 2026. You have to prepare accordingly as per the changed format. Practicing questions is an important part of the preparation.

Therefore we have a interactive Acids Bases And Salts 2 Marks Questions Answers for you.

Prepare from the NCERT textbook and revise from our Short Notes on Acids , Bases and Salts to get good marks.

Acids, Bases & Salts – Q1 to Q60

Acids, Bases & Salts – Questions 1 to 60

1. Indicators and Their Properties

Q1. A student tested a household cleaning solution with red litmus paper and observed that it turned blue.
(a) What does this indicate about the nature of the solution?
(b) Name one natural indicator other than litmus that could also be used.

(a) The solution is basic in nature.

(b) Turmeric or red cabbage extract.

Q2. In an activity, onion strips lose their smell when treated with NaOH but retain it with water.
(a) What category of indicator does onion belong to?
(b) Why does the odour disappear in basic medium?

(a) Onion is an olfactory indicator.

(b) The chemical responsible for the odour reacts with the base and gets neutralized.

Q3. A cloth stained with curry turns reddish-brown when washed with soap but becomes yellow again after rinsing with water.
(a) Identify the natural indicator present in curry.
(b) Explain why the colour changes with soap.

(a) Turmeric is the natural indicator in curry.

(b) Soap is basic, and turmeric turns reddish-brown in basic medium.

Q4. A student added phenolphthalein to a solution and observed a pink colour.
(a) What can be inferred about the pH of the solution?
(b) What would happen if excess HCl is added dropwise?

(a) The solution is basic (pH > 7).

(b) The pink colour would disappear as the base is neutralized by the acid.

Q5. Methyl orange is added to two test tubes—one containing vinegar and the other containing baking soda solution.
(a) Predict the colour in each test tube.
(b) Justify using the nature of the substances.

(a) Vinegar: red; Baking soda: yellow.

(b) Vinegar is acidic (turns methyl orange red); baking soda is basic (turns methyl orange yellow).

2. Reaction of Acids and Bases with Metals

Q6. Refer to Fig. 2.1. When zinc granules are added to dilute H₂SO₄, bubbles form in soap solution and a gas burns with a pop sound.
(a) Identify the gas evolved.
(b) Write the balanced chemical equation.
[Insert image for Fig. 2.1]
Figure 2.1: Reaction of zinc with dilute sulphuric acid

(a) Hydrogen gas (H₂).

(b) Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

Q7. A student repeats the experiment in Fig. 2.1 using copper instead of zinc. No gas is evolved.
(a) Why does copper not react with dilute H₂SO₄?
(b) What does this suggest about the reactivity of metals with acids?

(a) Copper is less reactive than hydrogen and cannot displace it from acids.

(b) Only metals above hydrogen in the reactivity series react with dilute acids to produce H₂ gas.

Q8. Sodium hydroxide solution is warmed with zinc granules.
(a) Name the gas evolved.
(b) Write the chemical formula of the salt formed.

(a) Hydrogen gas.

(b) Sodium zincate – Na₂ZnO₂.

Q9. Why is it unsafe to use highly reactive metals like potassium or sodium in the experiment shown in Fig. 2.1?

Because they react violently with acids, producing excessive heat and possibly causing explosion.

Q10. In Fig. 2.1, why is the gas passed through soap solution before testing?

To trap the gas in bubbles so it can be safely collected and tested with a burning candle.

3. Reaction with Metal Carbonates & Hydrogencarbonates

Q11. Refer to Fig. 2.2. When CO₂ from the reaction of Na₂CO₃ and HCl is passed through lime water, a white precipitate forms.
(a) Identify the white precipitate.
(b) Write the chemical equation.
[Insert image for Fig. 2.2]
Figure 2.2: Passing CO₂ through lime water

(a) Calcium carbonate (CaCO₃).

(b) Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)

Q12. If excess CO₂ is passed through the lime water in Fig. 2.2, the milkiness disappears.
(a) Why does this happen?
(b) Name the new compound formed.

(a) Insoluble calcium carbonate reacts with more CO₂ to form soluble calcium bicarbonate.

(b) Calcium bicarbonate – Ca(HCO₃)₂.

Q13. Both Na₂CO₃ and NaHCO₃ produce CO₂ when treated with HCl.
(a) Which one reacts more vigorously?
(b) Give a reason based on their chemical structure.

(a) NaHCO₃ (sodium hydrogencarbonate) reacts more vigorously.

(b) It has a loosely bound H⁺ that facilitates faster reaction with acid.

Q14. A metal compound ‘A’ reacts with HCl to produce a gas that extinguishes a burning candle. One product is CaCl₂.
(a) Identify compound ‘A’.
(b) Write the balanced equation.

(a) Calcium carbonate (CaCO₃).

(b) CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)

Q15. Why are baking soda and vinegar used in homemade fire extinguishers?

Because they react to produce CO₂ gas, which cuts off oxygen supply to the fire.

4. Neutralisation Reactions

Q16. In an activity, phenolphthalein turns pink in NaOH and colourless when HCl is added.
(a) What type of reaction occurs?
(b) Write the general equation.

(a) Neutralisation reaction.

(b) Acid + Base → Salt + Water

Q17. A farmer adds slaked lime to his field.
(a) What problem is he trying to solve?
(b) What is the chemical nature of slaked lime?

(a) The soil is too acidic; he is neutralizing it.

(b) Slaked lime [Ca(OH)₂] is a base.

Q18. Why is milk of magnesia used to treat acidity?

Because it contains Mg(OH)₂, a mild base that neutralizes excess stomach acid.

Q19. A bee sting causes pain due to methanoic acid.
(a) Suggest a household remedy.
(b) Explain the chemical principle involved.

(a) Apply baking soda (NaHCO₃) paste.

(b) Baking soda is basic and neutralizes the acidic sting.

Q20. Complete the reaction: H⁺(aq) + OH⁻(aq) → ?
What does this represent?

→ H₂O(l). This represents the net ionic equation of a neutralisation reaction.

5. Reaction of Metallic & Non-metallic Oxides

Q21. Copper oxide dissolves in HCl to give a blue-green solution.
(a) What salt is formed?
(b) What does this tell us about the nature of copper oxide?

(a) Copper(II) chloride (CuCl₂).

(b) It is a basic oxide (behaves like a base).

Q22. CO₂ is passed through Ca(OH)₂ solution, forming CaCO₃.
(a) What does this tell us about CO₂?
(b) Classify CO₂ as metallic or non-metallic oxide.

(a) CO₂ is acidic in nature.

(b) Non-metallic oxide.

Q23. Why do metallic oxides react with acids but not with bases?

Because metallic oxides are basic in nature, so they only react with acids to form salt and water.

Q24. Can CaO be used to neutralize acidic soil? Justify.

Yes, because CaO (quick lime) is a basic oxide that reacts with acids to neutralize them.

Q25. SO₂ gas is bubbled through NaOH solution.
(a) Predict the products.
(b) What type of oxide is SO₂?

(a) Sodium sulfite (Na₂SO₃) and water.

(b) Acidic oxide (non-metallic).

6. Common Features of Acids & Bases – Ions in Solution

Q26. Refer to Fig. 2.3. The bulb glows when HCl is used but not with glucose.
(a) Why does the bulb glow with HCl?
(b) What does this prove about acids?
[Insert image for Fig. 2.3]
Figure 2.3: Testing electrical conductivity

(a) Because HCl dissociates into H⁺ and Cl⁻ ions, which conduct electricity.

(b) Acids produce ions in aqueous solution and conduct electricity.

Q27. Dry HCl gas is passed over dry blue litmus paper. No colour change occurs.
(a) Why?
(b) What happens if the paper is moistened?

(a) H⁺ ions are not formed without water.

(b) It turns red because HCl ionizes in presence of water to give H⁺.

Q28. Why do alcohol and glucose not conduct electricity despite containing hydrogen?

Because they do not dissociate into H⁺ ions in water; only covalent molecules form.

Q29. What is the actual form of H⁺ ion in water? Write its formula.

Hydronium ion, H₃O⁺.

Q30. NaOH dissolves in water to give Na⁺ and OH⁻.
(a) What is such a base called?
(b) Are all bases soluble in water?

(a) Alkali.

(b) No, only water-soluble bases are alkalis.

7. pH Scale and Its Importance

Q31. Refer to Fig. 2.7. Lemon juice turns pH paper red, while soap solution turns it green.
(a) Approximate the pH of each.
(b) Which has higher H⁺ ion concentration?
[Insert image for Fig. 2.7]
Figure 2.7: pH of common substances

(a) Lemon juice: pH ≈ 2–3; Soap solution: pH ≈ 9–10.

(b) Lemon juice has higher H⁺ ion concentration.

Q32. Rainwater with pH 5.2 is collected in a river.
(a) Is this considered acid rain?
(b) How might it affect aquatic life?

(a) Yes, because pH < 5.6 defines acid rain.

(b) It lowers river pH, making survival difficult for aquatic organisms.

Q33. A person uses baking soda to brush teeth.
(a) What is the likely pH of baking soda?
(b) How does it help prevent tooth decay?

(a) pH > 7 (basic, approx. 8–9).

(b) It neutralizes acids in the mouth (pH < 5.5 causes enamel decay).

Q34. Two solutions A (pH = 3) and B (pH = 10) are mixed.
(a) Will the resulting solution be acidic, basic, or neutral?
(b) What type of reaction occurs between them?

(a) Depends on quantities, but likely near neutral due to neutralisation.

(b) Neutralisation reaction.

Q35. Why do farmers test soil pH before cultivation?

Because plants require a specific pH range for healthy growth; unsuitable pH affects nutrient availability.

8. Salts – Family, pH, and Preparation

Q36. Sodium chloride and potassium chloride are both white crystalline solids.
(a) To which salt family do they belong?
(b) Are their aqueous solutions acidic, basic, or neutral?

(a) Chloride salt family.

(b) Neutral (pH = 7).

Q37. A salt solution turns red litmus blue.
(a) What can you infer about the parent acid and base?
(b) Give one example of such a salt.

(a) It is formed from a strong base and weak acid.

(b) Sodium carbonate (Na₂CO₃) or sodium acetate.

Q38. Aluminium chloride solution turns blue litmus red.
(a) Why is it acidic?
(b) Identify the parent acid and base.

(a) It is a salt of strong acid (HCl) and weak base [Al(OH)₃], so hydrolyses to give H⁺ ions.

(b) Acid: HCl; Base: Al(OH)₃.

Q39. Classify the following salts into families:
Na₂SO₄, K₂SO₄, NaNO₃, KNO₃

Sulphate family: Na₂SO₄, K₂SO₄
Nitrate family: NaNO₃, KNO₃

Q40. Why is NaCl neutral while Na₂CO₃ is basic?

NaCl is from strong acid (HCl) and strong base (NaOH); Na₂CO₃ is from strong base (NaOH) and weak acid (H₂CO₃).

9. Chemicals from Common Salt – Chlor-alkali Process

Q41. Refer to Fig. 2.8. In the chlor-alkali process:
(a) Name the gas evolved at the anode.
(b) What is the use of the solution formed near the cathode?
[Insert image for Fig. 2.8]
Figure 2.8: Chlor-alkali process products

(a) Chlorine gas (Cl₂).

(b) Sodium hydroxide solution—used in soap, paper, and textile industries.

Q42. Write the balanced equation for the chlor-alkali process. Name all products.

2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂(g) + H₂(g)

Products: Sodium hydroxide, chlorine gas, hydrogen gas.

Q43. Why is the process called “chlor-alkali”?

Because it produces “chlor” (chlorine) and “alkali” (sodium hydroxide).

Q44. Hydrogen gas is a by-product of the chlor-alkali process.
(a) Suggest one industrial use of this H₂.
(b) Is it acidic, basic, or neutral?

(a) Used in hydrogenation of oils or as rocket fuel.

(b) Neutral gas.

Q45. Can solid NaCl undergo electrolysis to give NaOH? Why or why not?

No, because ions are not free to move in solid state; aqueous solution (brine) is required.

10. Bleaching Powder, Baking Soda, Washing Soda

Q46. Bleaching powder is represented as CaOCl₂.
(a) What is its chemical name?
(b) How is it prepared? Write the equation.

(a) Calcium oxychloride.

(b) Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Q47. Why is bleaching powder used to disinfect drinking water?

Because it releases chlorine, which kills germs.

Q48. Baking soda is added to cake batter.
(a) What gas is released on heating?
(b) Write the decomposition reaction.

(a) Carbon dioxide (CO₂).

(b) 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

Q49. Why is tartaric acid added to baking soda to make baking powder?

To neutralize the bitter taste of Na₂CO₃ formed and to provide H⁺ for faster CO₂ release in dough.

Q50. Washing soda is used to remove permanent hardness of water.
(a) What causes permanent hardness?
(b) How does washing soda remove it?

(a) Presence of chlorides and sulphates of Ca²⁺/Mg²⁺.

(b) It reacts to form insoluble carbonates that precipitate out.

11. Water of Crystallisation

Q51. Refer to Fig. 2.9. Blue crystals of CuSO₄ turn white on heating.
(a) What is lost during heating?
(b) Write the formula of hydrated and anhydrous copper sulphate.
[Insert image for Fig. 2.9]
Figure 2.9: Removing water of crystallisation

(a) Water of crystallisation.

(b) Hydrated: CuSO₄·5H₂O; Anhydrous: CuSO₄

Q52. When water is added to anhydrous CuSO₄, it turns blue again.
(a) Is this a physical or chemical change?
(b) What does this indicate about water of crystallisation?

(a) Chemical change (reversible hydration).

(b) Water is chemically bound in the crystal structure.

Q53. Gypsum is heated to make Plaster of Paris.
(a) Write the chemical formula of gypsum.
(b) At what temperature is it heated?

(a) CaSO₄·2H₂O

(b) 373 K

Q54. Why is Plaster of Paris stored in moisture-proof containers?

Because it absorbs moisture and hardens into gypsum.

Q55. What does “½H₂O” in CaSO₄·½H₂O signify?

Two formula units of CaSO₄ share one molecule of water.

12. pH in Everyday Life – Digestion, Tooth Decay, Bee Stings

Q56. A person experiences pain due to excess stomach acid.
(a) Name a mild base commonly used as an antacid.
(b) Write the chemical equation for its reaction with HCl.

(a) Magnesium hydroxide or baking soda.

(b) Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O

Q57. Why does tooth decay begin when mouth pH drops below 5.5?

Tooth enamel (calcium hydroxyapatite) starts corroding below pH 5.5 due to acid produced by bacterial action on food particles.

Q58. After eating sweets, a child develops toothache.
(a) What causes this?
(b) How can brushing with basic toothpaste help?

(a) Bacteria degrade sugar to produce acid, lowering pH and damaging enamel.

(b) Basic toothpaste neutralizes acid and raises pH above 5.5, preventing decay.

Q59. A bee sting leaves methanoic acid on the skin.
(a) Suggest a household remedy.
(b) What type of reaction occurs?

(a) Apply baking soda paste.

(b) Neutralisation reaction.

Q60. Nettle leaves cause burning pain due to methanoic acid.
(a) Why does rubbing dock plant leaf help?
(b) What is the likely pH of dock plant extract?

(a) Dock plant contains a base that neutralizes the acid.

(b) pH > 7 (basic).

Acids, Bases & Salts – Questions 61 to 100

13. Soil pH and Agriculture

Q61. A farmer finds his crop yield decreasing. Soil test shows pH = 4.5.
(a) Is the soil acidic or basic?
(b) Which substance should he add—slaked lime, vinegar, or lemon juice?

(a) Acidic (pH < 7).

(b) Slaked lime [Ca(OH)₂].

Q62. Why do different crops require different soil pH ranges?

Because nutrient availability and microbial activity depend on pH; plants absorb minerals optimally only within specific pH ranges.

14. Acid Rain

Q63. Rainwater has pH = 4.8.
(a) Is it acid rain? Justify.
(b) Name one pollutant responsible for acid rain.

(a) Yes, because pH < 5.6 defines acid rain.

(b) SO₂ or NO₂.

Q64. How does acid rain affect statues made of marble?

It reacts with CaCO₃ (marble) to form soluble calcium compounds, causing erosion.

15. Properties and Uses of Common Salt Derivatives

Q65. Why is common salt (NaCl) considered a raw material for many chemicals?

Because it is used to produce NaOH, Cl₂, H₂, bleaching powder, baking soda, and washing soda via the chlor-alkali process.

Q66. Rock salt appears brown. Why?

Due to impurities present in it.

16. Bleaching Powder

Q67. Write the chemical equation for preparation of bleaching powder.

Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Q68. Why is bleaching powder used in paper factories?

To bleach wood pulp.

Q69. How does bleaching powder disinfect drinking water?

It releases chlorine, which kills germs.

17. Baking Soda and Baking Powder

Q70. What happens when baking soda is heated? Write the equation.

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

Q71. Why is tartaric acid added to baking soda to make baking powder?

To neutralize the bitter taste of Na₂CO₃ and provide H⁺ for faster CO₂ release in dough.

Q72. How does baking soda act as an antacid?

Being basic, it neutralizes excess stomach acid.

Q73. In a soda-acid fire extinguisher (Fig. 2.10), what gas is produced? How does it extinguish fire?
[Insert image for Fig. 2.10]
Figure 2.10: Soda-acid fire extinguisher setup

CO₂ gas; it cuts off oxygen supply to the fire.

18. Washing Soda

Q74. What is the chemical formula of washing soda?

Na₂CO₃·10H₂O

Q75. How is washing soda obtained from baking soda?

By heating baking soda to get Na₂CO₃, then recrystallising it to form Na₂CO₃·10H₂O.

Q76. Why is washing soda used to remove permanent hardness of water?

It reacts with Ca²⁺/Mg²⁺ chlorides/sulphates to form insoluble carbonates that precipitate out.

Q77. List two industrial uses of washing soda.

Used in glass, soap, and paper industries; also in manufacturing borax.

19. Water of Crystallisation

Q78. Refer to Fig. 2.9. Blue CuSO₄ turns white on heating.
(a) What is lost?
(b) What is the name of the white powder formed?
[Insert image for Fig. 2.9]
Figure 2.9: Removing water of crystallisation

(a) Water of crystallisation.

(b) Anhydrous copper sulphate.

Q79. What does “10H₂O” in Na₂CO₃·10H₂O mean? Is the solid wet?

It means 10 water molecules are chemically bound per formula unit; the solid is dry (not wet).

Q80. Gypsum is heated to make Plaster of Paris.
(a) Write the balanced equation.
(b) At what temperature?

(a) CaSO₄·2H₂O → CaSO₄·½H₂O + 1½H₂O

(b) 373 K

Q81. Why is Plaster of Paris called “hemihydrate”?

Because two formula units of CaSO₄ share one water molecule (½ H₂O per CaSO₄ unit).

Q82. Why must Plaster of Paris be stored in moisture-proof containers?

It absorbs moisture and hardens into gypsum.

Q83. What happens when water is added to Plaster of Paris? Write the equation.

CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O

20. Miscellaneous Application-Based Questions

Q84. Why should curd not be stored in copper vessels?

Because acids in curd react with copper to form toxic salts.

Q85. A gas extinguishes a burning candle and turns lime water milky. Identify the gas and the salt that produced it with HCl.

Gas: CO₂; Salt: Calcium carbonate (CaCO₃).

Q86. Why do glucose and alcohol not conduct electricity despite having hydrogen?

They do not dissociate into H⁺ ions in water; only covalent molecules form.

Q87. Dry HCl gas does not change dry blue litmus colour. Why?

H⁺ ions form only in aqueous solution; dry HCl cannot ionize without water.

Q88. Why is dilution of concentrated H₂SO₄ exothermic?

Because hydration of H₂SO₄ releases large amount of heat.

Q89. Solution A has pH = 3, Solution B has pH = 10.
(a) Which has higher H⁺ concentration?
(b) Which will turn red litmus blue?

(a) Solution A.

(b) Solution B.

Q90. Classify the following salts as acidic, basic, or neutral:
(a) NH₄Cl (b) CH₃COONa (c) NaCl

(a) Acidic (strong acid + weak base)
(b) Basic (weak acid + strong base)
(c) Neutral (strong acid + strong base)

Q91. In the chlor-alkali process, why is brine used instead of solid NaCl?

Because ions must be mobile to conduct electricity; solid NaCl has fixed ions.

Q92. What is the role of chlorine in bleaching?

It acts as an oxidizing agent, breaking colour-producing compounds.

Q93. Fresh milk has pH ≈ 6. On turning into curd, pH decreases. Why?

Lactic acid is produced during fermentation, lowering pH.

Q94. A milkman adds baking soda to milk.
(a) Why does it delay curdling?
(b) Is this practice advisable?

(a) Baking soda makes milk slightly alkaline, neutralizing lactic acid and delaying pH drop needed for curd formation.

(b) Not advisable—it masks spoilage and reduces nutritional quality.

Q95. Complete the analogy:
Litmus : Lichen :: Turmeric : ________

Turmeric root (or Curcuma longa plant).

Q96. Why is pH of saliva tested before and after meals?

To monitor acid production; pH drops after meals due to bacterial action on food, increasing risk of tooth decay.

Q97. What is the pH of 1M NaOH? Is it strong or weak base?

pH ≈ 14; it is a strong base (fully dissociates to give OH⁻ ions).

Q98. Why is vinegar used as a preservative in pickles?

Because its acidic nature prevents growth of bacteria and fungi.

Q99. What happens when CO₂ is passed through sodium hydroxide solution?

2NaOH + CO₂ → Na₂CO₃ + H₂O

Q100. Why is rainwater slightly acidic even without pollution?

Because atmospheric CO₂ dissolves in rainwater to form weak carbonic acid:
CO₂ + H₂O → H₂CO₃

FAQs

Are the questions sufficient?

The questions are for practice and may appear in the examinations. Maximum or all the questions can be prepared from the NCERT textbook itself.

How many times shall I revise the chapter Acids, Bases and Salts

It depends on your retention capacity. Revising 20 to 30 times after you have prepared the chapter will do.

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