Introduction – Class X Science, Chapter 2: Acids, Bases and Salts
Acids, bases, and salts are an important part of our everyday life. From the food we eat to the medicines we use, many common substances show acidic or basic nature. This chapter helps students understand what acids, bases, and salts are, how they behave, and why they are useful. It explains their properties, reactions, strength using the pH scale, and their role in daily activities such as digestion, cleaning, agriculture, and industry. A clear understanding of this chapter builds a strong foundation for chemistry and is very important for Class X board examinations.
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Class X Science
Chapter 2: Acids, Bases and Salts
100 Important Facts
1. Acids, bases, and salts are common chemicals used in daily life.
2. An acid produces hydrogen ions (H⁺) in aqueous solution.
3. A base produces hydroxide ions (OH⁻) in aqueous solution.
4. A salt is formed by the reaction of an acid and a base.
5. Acids taste sour.
6. Bases taste bitter and feel soapy.
7. Acids turn blue litmus red.
8. Bases turn red litmus blue.
9. Litmus is a natural indicator obtained from lichens.
10. Acids show acidic nature only in aqueous solution.
11. Dry HCl gas does not show acidic properties.
12. Bases also need water to show basic nature.
13. Strong acids ionize completely in water.
14. Weak acids ionize partially in water.
15. Examples of strong acids are HCl and H₂SO₄.
16. Examples of weak acids are acetic acid and carbonic acid.
17. Strong bases include NaOH and KOH.
18. Weak bases include ammonium hydroxide.
19. pH scale ranges from 0 to 14.
20. pH value of 7 is neutral.
21. pH less than 7 indicates an acidic solution.
22. pH more than 7 indicates a basic solution.
23. Lower the pH, stronger the acid.
24. Higher the pH, stronger the base.
25. The pH of pure water is 7.
26. pH of human blood is about 7.4.
27. pH of gastric juice is about 1–2.
28. pH of acid rain is less than 5.6.
29. Tooth decay occurs when pH falls below 5.5.
30. Antacids are basic substances.
31. Antacids neutralize excess acid in the stomach.
32. Baking soda is sodium hydrogen carbonate (NaHCO₃).
33. Baking soda is a mild base.
34. Washing soda is sodium carbonate (Na₂CO₃·10H₂O).
35. Washing soda is used as a cleaning agent.
36. Plaster of Paris is calcium sulphate hemihydrate.
37. Chemical formula of Plaster of Paris is CaSO₄·½H₂O.
38. Plaster of Paris is prepared from gypsum.
39. Gypsum is calcium sulphate dihydrate (CaSO₄·2H₂O).
40. Plaster of Paris sets by absorbing water.
41. Common salt is sodium chloride (NaCl).
42. Common salt is obtained from seawater.
43. Salts may be acidic, basic, or neutral.
44. Sodium chloride is a neutral salt.
45. Ammonium chloride is an acidic salt.
46. Sodium carbonate is a basic salt.
47. Acids react with metals to produce hydrogen gas.
48. Acids do not react with noble metals like gold.
49. Acids react with metal carbonates to form CO₂.
50. Carbon dioxide turns lime water milky.
51. Lime water is calcium hydroxide solution.
52. Bases react with acids to form salt and water.
53. This reaction is called neutralization.
54. Bases react with non-metal oxides.
55. Alkalis are bases soluble in water.
56. Sodium hydroxide is an alkali.
57. Potassium hydroxide is an alkali.
58. Bleaching powder is calcium oxychloride.
59. Chemical formula of bleaching powder is CaOCl₂.
60. Bleaching powder is used as a disinfectant.
61. Bleaching powder is used for bleaching cotton and linen.
62. Bleaching powder releases chlorine gas.
63. Baking powder contains baking soda and tartaric acid.
64. Baking powder is used in baking cakes.
65. Washing soda is used in glass and soap industries.
66. Washing soda removes permanent hardness of water.
67. pH of rainwater is slightly acidic.
68. Excess use of acids can harm soil fertility.
69. Bases like calcium hydroxide are used to treat acidic soil.
70. Acid rain damages monuments.
71. Taj Mahal is affected by acid rain.
72. Indicators change color in acidic or basic solutions.
73. Phenolphthalein is a synthetic indicator.
74. Phenolphthalein turns pink in basic solution.
75. Methyl orange is another synthetic indicator.
76. Methyl orange turns red in acid.
77. Universal indicator shows different colors for different pH.
78. Sodium hydroxide is used in soap making.
79. Sodium hydroxide is also called caustic soda.
80. Calcium hydroxide is called slaked lime.
81. Calcium oxide is called quick lime.
82. Quick lime reacts with water to form slaked lime.
83. Slaked lime is used in whitewashing.
84. During whitewashing, calcium carbonate is formed.
85. Hard water does not lather with soap easily.
86. Soft water lathers easily with soap.
87. Acids are corrosive in nature.
88. Bases can also be corrosive.
89. Proper handling of acids and bases is necessary.
90. pH scale was developed by Sørensen.
91. Salts can be hydrated or anhydrous.
92. Hydrated salts contain water of crystallization.
93. Blue vitriol is copper sulphate pentahydrate.
94. Chemical formula of blue vitriol is CuSO₄·5H₂O.
95. Loss of water of crystallization changes color.
96. Heating gypsum gives Plaster of Paris.
97. Plaster of Paris is used to make toys and casts.
98. Acids and bases play an important role in daily life.
99. Correct pH balance is essential for living organisms.
100. Acids, bases, and salts are essential topics for Class X exams.
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Here are 50 MCQs with Answers from Class X Science – Chapter 2: Acids, Bases and Salts,
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Class X Science
Chapter 2: Acids, Bases and Salts
50 MCQs with Answers
1. Which of the following is an acid?
A) NaOH
B) KOH
C) HCl
D) CaO
✅ Answer: C
2. Which substance turns blue litmus red?
A) Base
B) Salt
C) Acid
D) Neutral solution
✅ Answer: C
3. Which ion is responsible for acidic nature?
A) OH⁻
B) H⁺
C) Na⁺
D) Cl⁻
✅ Answer: B
4. Which ion is responsible for basic nature?
A) H⁺
B) Na⁺
C) OH⁻
D) Cl⁻
✅ Answer: C
5. pH value of a neutral solution is:
A) 0
B) 5
C) 7
D) 14
✅ Answer: C
6. Which acid is present in lemon?
A) Acetic acid
B) Citric acid
C) Lactic acid
D) Oxalic acid
✅ Answer: B
7. Which base is known as caustic soda?
A) Ca(OH)₂
B) NaOH
C) KOH
D) NH₄OH
✅ Answer: B
8. Which gas is released when acid reacts with metal?
A) Oxygen
B) Nitrogen
C) Hydrogen
D) Carbon dioxide
✅ Answer: C
9. Which substance is used as an antacid?
A) HCl
B) NaOH
C) Mg(OH)₂
D) NaCl
✅ Answer: C
10. Which salt is used in baking powder?
A) Washing soda
B) Baking soda
C) Bleaching powder
D) Common salt
✅ Answer: B
11. Baking soda is chemically known as:
A) Na₂CO₃
B) NaHCO₃
C) CaCO₃
D) NaCl
✅ Answer: B
12. Washing soda is:
A) Na₂CO₃·10H₂O
B) NaHCO₃
C) CaSO₄
D) NaCl
✅ Answer: A
13. Plaster of Paris is obtained from:
A) Limestone
B) Gypsum
C) Marble
D) Chalk
✅ Answer: B
14. Chemical formula of Plaster of Paris is:
A) CaSO₄
B) CaSO₄·2H₂O
C) CaSO₄·½H₂O
D) CaCO₃
✅ Answer: C
15. Which indicator turns pink in a basic solution?
A) Litmus
B) Methyl orange
C) Phenolphthalein
D) Turmeric
✅ Answer: C
16. Which indicator turns red in acidic solution?
A) Phenolphthalein
B) Methyl orange
C) Turmeric
D) China rose
✅ Answer: B
17. pH value of strong acids is generally:
A) Less than 7
B) Equal to 7
C) Greater than 7
D) Equal to 14
✅ Answer: A
18. Tooth decay starts when pH of mouth falls below:
A) 7
B) 6
C) 5.5
D) 4
✅ Answer: C
19. Acid rain has pH value:
A) 7
B) More than 7
C) Less than 5.6
D) Equal to 14
✅ Answer: C
20. Which substance is used to treat acidic soil?
A) Sodium chloride
B) Calcium hydroxide
C) Ammonium chloride
D) Hydrochloric acid
✅ Answer: B
21. Bleaching powder is used for:
A) Cleaning metals
B) Disinfecting water
C) Making glass
D) Coloring clothes
✅ Answer: B
22. Chemical formula of bleaching powder is:
A) CaCl₂
B) Ca(OH)₂
C) CaOCl₂
D) CaCO₃
✅ Answer: C
23. Common salt is chemically:
A) Na₂CO₃
B) NaHCO₃
C) NaCl
D) CaCl₂
✅ Answer: C
24. Which salt is neutral in nature?
A) NH₄Cl
B) Na₂CO₃
C) NaCl
D) CuSO₄
✅ Answer: C
25. Which salt is acidic in nature?
A) NaCl
B) Na₂CO₃
C) NH₄Cl
D) CaCO₃
✅ Answer: C
26. Which salt is basic in nature?
A) NaCl
B) Na₂CO₃
C) NH₄Cl
D) CuSO₄
✅ Answer: B
27. What is the pH of pure water?
A) 0
B) 5
C) 7
D) 14
✅ Answer: C
28. Which acid is present in curd?
A) Acetic acid
B) Citric acid
C) Lactic acid
D) Oxalic acid
✅ Answer: C
29. Which base is present in soap?
A) HCl
B) NaOH
C) H₂SO₄
D) HNO₃
✅ Answer: B
30. Which substance does not show acidic nature without water?
A) H₂SO₄
B) HCl gas
C) HNO₃
D) CH₃COOH
✅ Answer: B
31. Which gas turns lime water milky?
A) Oxygen
B) Hydrogen
C) Carbon dioxide
D) Nitrogen
✅ Answer: C
32. Lime water is a solution of:
A) CaCO₃
B) CaCl₂
C) Ca(OH)₂
D) CaSO₄
✅ Answer: C
33. Which acid is present in vinegar?
A) Formic acid
B) Acetic acid
C) Citric acid
D) Lactic acid
✅ Answer: B
34. Which base is also called slaked lime?
A) CaO
B) Ca(OH)₂
C) NaOH
D) KOH
✅ Answer: B
35. Quick lime is:
A) CaCO₃
B) Ca(OH)₂
C) CaO
D) CaSO₄
✅ Answer: C
36. Which salt is used to remove hardness of water?
A) Baking soda
B) Washing soda
C) Bleaching powder
D) Common salt
✅ Answer: B
37. Hard water does not lather easily with:
A) Detergent
B) Shampoo
C) Soap
D) Acid
✅ Answer: C
38. Universal indicator shows:
A) Only red color
B) Only blue color
C) Different colors for different pH
D) No color change
✅ Answer: C
39. Which compound is used for whitewashing?
A) CaO
B) Ca(OH)₂
C) CaCO₃
D) CaSO₄
✅ Answer: B
40. Blue vitriol is:
A) CuSO₄·5H₂O
B) CuSO₄
C) FeSO₄
D) ZnSO₄
✅ Answer: A
41. Loss of water of crystallization causes:
A) Increase in mass
B) Change in color
C) Explosion
D) Neutralization
✅ Answer: B
42. Which acid is used in car batteries?
A) Nitric acid
B) Hydrochloric acid
C) Sulphuric acid
D) Acetic acid
✅ Answer: C
43. Which base is used in making paper and soap?
A) NaOH
B) Ca(OH)₂
C) NH₄OH
D) K₂CO₃
✅ Answer: A
44. Which salt is used as a disinfectant?
A) NaCl
B) CaOCl₂
C) Na₂CO₃
D) NaHCO₃
✅ Answer: B
45. Which reaction produces salt and water?
A) Oxidation
B) Reduction
C) Neutralization
D) Decomposition
✅ Answer: C
46. Bases generally taste:
A) Sour
B) Sweet
C) Bitter
D) Salty
✅ Answer: C
47. Acids are generally:
A) Slippery
B) Corrosive
C) Neutral
D) Oily
✅ Answer: B
48. Which salt is used in glass industry?
A) Washing soda
B) Baking soda
C) Common salt
D) Bleaching powder
✅ Answer: A
49. Which substance neutralizes acid in soil?
A) HCl
B) NaCl
C) Ca(OH)₂
D) NH₄Cl
✅ Answer: C
50. Acids, bases, and salts are important because they:
A) Are only laboratory chemicals
B) Have no daily use
C) Are used in daily life
D) Are radioactive
✅ Answer: C
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