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9-10th Class

Acids Bases And Salts notes in easy words

Afifa Asad 0

1. Introduction

Acids, bases, and salts are three important classes of chemical substances that play a vital role in chemistry and everyday life. From digestion in our stomach to industrial manufacturing, these substances are involved in numerous chemical processes. The study of acids and bases helps us understand reactions, pH balance, soil treatment, medicines, cleaning agents, and environmental issues.

Early scientists defined acids and bases based on their taste and properties. However, modern chemistry explains their behavior using different theories such as Arrhenius theory, Brønsted–Lowry theory, and Lewis theory.

2. Acids

2.1 Definition of Acids

According to Arrhenius theory, an acid is a substance that produces hydrogen ions (H⁺) in aqueous solution.

Example:
HCl (aq) → H⁺ (aq) + Cl⁻ (aq)

According to Brønsted–Lowry theory, an acid is a proton (H⁺) donor.

According to Lewis theory, an acid is an electron pair acceptor.

2.2 Physical Properties of Acids

  1. Sour in taste (e.g., lemon juice contains citric acid)
  2. Turn blue litmus red
  3. Conduct electricity in aqueous solution
  4. Corrosive in nature
  5. Have pH less than 7

2.3 Chemical Properties of Acids

(a) Reaction with Metals

Acids react with metals to produce salt and hydrogen gas.

Zn + 2HCl → ZnCl₂ + H₂↑

(b) Reaction with Metal Carbonates

Acids react with carbonates to produce salt, water, and carbon dioxide.

Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

(c) Reaction with Bases (Neutralization)

Acid + Base → Salt + Water

HCl + NaOH → NaCl + H₂O

2.4 Types of Acids

(1) Based on Strength

  • Strong acids: HCl, H₂SO₄, HNO₃
  • Weak acids: CH₃COOH, H₂CO₃

(2) Based on Origin

  • Organic acids: Acetic acid, Citric acid
  • Mineral acids: Hydrochloric acid, Sulphuric acid

2.5 Important Acids and Their Uses

  • Hydrochloric acid (HCl): Used in cleaning metals and digestion in stomach
  • Sulphuric acid (H₂SO₄): Used in batteries and fertilizer production
  • Nitric acid (HNO₃): Used in explosives and fertilizers

3. Bases

3.1 Definition of Bases

According to Arrhenius theory, a base produces hydroxide ions (OH⁻) in aqueous solution.

NaOH → Na⁺ + OH⁻

According to Brønsted–Lowry theory, a base is a proton acceptor.

According to Lewis theory, a base is an electron pair donor.

3.2 Physical Properties of Bases

  1. Bitter in taste
  2. Slippery to touch
  3. Turn red litmus blue
  4. Conduct electricity in aqueous solution
  5. pH greater than 7

3.3 Chemical Properties of Bases

(a) Reaction with Acids

Base + Acid → Salt + Water

KOH + HCl → KCl + H₂O

(b) Reaction with Non-metal Oxides

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

3.4 Alkalis

Bases that dissolve in water are called alkalis.

Examples:

  • Sodium hydroxide (NaOH)
  • Potassium hydroxide (KOH)
  • Calcium hydroxide (Ca(OH)₂)

4. Salts

4.1 Definition

A salt is formed when hydrogen ion of an acid is replaced by a metal or ammonium ion.

Example:
NaCl is formed from HCl and NaOH.

4.2 Types of Salts

  1. Neutral salts – NaCl
  2. Acidic salts – NH₄Cl
  3. Basic salts – Na₂CO₃

4.3 Properties of Salts

  • May be acidic, basic, or neutral
  • Conduct electricity in molten or aqueous state
  • High melting points

5. Strength of Acids and Bases

Strength depends on degree of ionization.

Strong acids ionize completely:
HCl → H⁺ + Cl⁻

Weak acids ionize partially:
CH₃COOH ⇌ CH₃COO⁻ + H⁺

6. pH Scale

The pH scale measures acidity or basicity of a solution.

Range: 0 to 14

  • pH < 7 → Acidic
  • pH = 7 → Neutral
  • pH > 7 → Basic

Lower pH means stronger acid. Higher pH means stronger base.

6.1 Importance of pH in Everyday Life

  1. pH of stomach – HCl helps digestion
  2. Tooth decay – pH below 5.5 causes decay
  3. Soil pH – Affects crop growth
  4. pH of rain – Acid rain damages environment

7. Indicators

Indicators are substances that change color in acidic or basic solutions.

Types:

  1. Natural Indicators
    • Litmus
    • Turmeric
    • China rose
  2. Synthetic Indicators
    • Phenolphthalein
    • Methyl orange
  3. Universal Indicator
    Shows color change for entire pH range.

8. Neutralization Reaction

Neutralization is reaction between acid and base forming salt and water.

Example:
HCl + NaOH → NaCl + H₂O

Applications:

  • Treating indigestion (antacids)
  • Soil treatment
  • Treating insect stings

9. Common Salts and Their Importance

9.1 Sodium Chloride (NaCl)

Obtained from sea water. Used in food and chemical industry.

9.2 Washing Soda (Na₂CO₃·10H₂O)

Preparation:
2NaCl + CaCO₃ + NH₃ → Na₂CO₃

Uses:

  • Cleaning agent
  • Softening hard water
  • Glass manufacturing

9.3 Baking Soda (NaHCO₃)

Preparation:
NaCl + NH₃ + H₂O + CO₂ → NaHCO₃

Uses:

  • Baking
  • Fire extinguishers
  • Antacid

9.4 Plaster of Paris (CaSO₄·½H₂O)

Prepared by heating gypsum.

Uses:

  • Making statues
  • Medical casts
  • Decorative materials

10. Water of Crystallization

Some salts contain fixed number of water molecules in crystalline form.

Example:
CuSO₄·5H₂O (Blue vitriol)

On heating, water is removed and color changes.

11. Hard and Soft Water

Hard water contains calcium and magnesium salts. It does not form lather easily.

Temporary hardness: Due to bicarbonates
Permanent hardness: Due to chlorides and sulphates

Removal methods:

  • Boiling
  • Adding washing soda

12. Acid Rain

Acid rain is caused by reaction of rainwater with SO₂ and NO₂ gases.

Effects:

  • Damages crops
  • Corrodes buildings
  • Harms aquatic life

13. Safety Measures

  • Handle acids and bases carefully
  • Always add acid to water, not water to acid
  • Wear gloves and goggles
  • Store properly

14. Applications in Daily Life

  1. Antacids neutralize stomach acid
  2. Fertilizers contain ammonium salts
  3. Soaps and detergents are basic
  4. Batteries use sulphuric acid
  5. Toothpaste is basic to prevent decay

15. Conclusion

Acids, bases, and salts form the foundation of many chemical reactions and industrial processes. Their properties help us understand neutralization, pH balance, corrosion, environmental issues, and manufacturing of essential materials. The pH scale provides a scientific method to measure acidity and basicity, which is crucial in medicine, agriculture, and environmental science. Understanding these concepts enables us to apply chemistry in daily life effectively and safely. Proper handling and awareness of their reactions ensure safety and environmental protection.

Here are 100 MCQs with Answers from Acids, Bases and Salts (Class 10 Level)

1–20

  1. An acid produces which ion in aqueous solution?
    a) OH⁻
    b) H⁺
    c) Na⁺
    d) Cl⁻
    Answer: b
  2. A base produces which ion in water?
    a) H⁺
    b) Cl⁻
    c) OH⁻
    d) O²⁻
    Answer: c
  3. The pH of a neutral solution is:
    a) 0
    b) 7
    c) 14
    d) 1
    Answer: b
  4. Which is a strong acid?
    a) CH₃COOH
    b) HCl
    c) H₂CO₃
    d) Citric acid
    Answer: b
  5. Which is a weak acid?
    a) HNO₃
    b) H₂SO₄
    c) CH₃COOH
    d) HCl
    Answer: c
  6. Which indicator turns red in acid?
    a) Blue litmus
    b) Red litmus
    c) Phenolphthalein
    d) Turmeric
    Answer: a
  7. Phenolphthalein turns pink in:
    a) Acid
    b) Base
    c) Neutral
    d) Salt
    Answer: b
  8. The reaction between acid and base is called:
    a) Oxidation
    b) Reduction
    c) Neutralization
    d) Decomposition
    Answer: c
  9. Baking soda formula is:
    a) Na₂CO₃
    b) NaHCO₃
    c) CaCO₃
    d) NH₄Cl
    Answer: b
  10. Washing soda formula is:
    a) Na₂CO₃·10H₂O
    b) NaHCO₃
    c) CaSO₄
    d) NaCl
    Answer: a
  11. Plaster of Paris formula is:
    a) CaSO₄
    b) CaSO₄·2H₂O
    c) CaSO₄·½H₂O
    d) CaCO₃
    Answer: c
  12. Gypsum formula is:
    a) CaSO₄·2H₂O
    b) CaSO₄·½H₂O
    c) Na₂CO₃
    d) NaHCO₃
    Answer: a
  13. Acid rain contains mainly:
    a) HCl
    b) H₂SO₄ and HNO₃
    c) NaOH
    d) NH₄OH
    Answer: b
  14. Which acid is present in stomach?
    a) HNO₃
    b) HCl
    c) H₂SO₄
    d) CH₃COOH
    Answer: b
  15. Tooth decay occurs when pH falls below:
    a) 7
    b) 6.5
    c) 5.5
    d) 8
    Answer: c
  16. Which is an alkali?
    a) CuO
    b) NaOH
    c) CO₂
    d) SO₂
    Answer: b
  17. Litmus is obtained from:
    a) Flower
    b) Algae
    c) Lichen
    d) Tree bark
    Answer: c
  18. Which salt is neutral?
    a) NaCl
    b) NH₄Cl
    c) Na₂CO₃
    d) HCl
    Answer: a
  19. Which gas is released when acid reacts with metal carbonate?
    a) H₂
    b) O₂
    c) CO₂
    d) N₂
    Answer: c
  20. Which acid is used in car batteries?
    a) HCl
    b) HNO₃
    c) H₂SO₄
    d) CH₃COOH
    Answer: c

21–40

  1. Strong bases ionize:
    a) Partially
    b) Completely
    c) Not at all
    d) Slowly
    Answer: b
  2. Red litmus turns blue in:
    a) Acid
    b) Base
    c) Neutral
    d) Salt
    Answer: b
  3. Which compound causes temporary hardness?
    a) Ca(HCO₃)₂
    b) CaCl₂
    c) NaCl
    d) KCl
    Answer: a
  4. Which removes temporary hardness?
    a) Boiling
    b) Cooling
    c) Freezing
    d) Filtering
    Answer: a
  5. Turmeric turns reddish brown in:
    a) Acid
    b) Base
    c) Neutral
    d) Salt
    Answer: b
  6. A solution with pH 2 is:
    a) Basic
    b) Neutral
    c) Strongly acidic
    d) Weakly basic
    Answer: c
  7. NaOH is commonly known as:
    a) Washing soda
    b) Caustic soda
    c) Baking soda
    d) Slaked lime
    Answer: b
  8. Ca(OH)₂ is called:
    a) Quick lime
    b) Slaked lime
    c) Gypsum
    d) POP
    Answer: b
  9. NH₄Cl is:
    a) Basic salt
    b) Neutral salt
    c) Acidic salt
    d) Strong acid
    Answer: c
  10. Universal indicator gives:
    a) One color
    b) Two colors
    c) Many colors
    d) No color
    Answer: c

31–60

  1. HCl in water forms: H₃O⁺ and Cl⁻
    Answer: a (True option style)
  2. Acid + Metal → Salt + Hydrogen
    Answer: a
  3. Acid + Base → Salt + Water
    Answer: a
  4. Na₂CO₃ is basic salt
    Answer: a
  5. Water of crystallization is fixed water in salt
    Answer: a
  6. Blue vitriol is: CuSO₄·5H₂O
    Answer: b
  7. POP is prepared by heating:
    a) Gypsum
    b) CaCO₃
    c) NaCl
    d) Na₂CO₃
    Answer: a
  8. Strong acids have pH:
    a) 0–3
    b) 7
    c) 8–14
    d) 6
    Answer: a
  9. Weak bases ionize:
    a) Completely
    b) Partially
    c) Fully
    d) Rapidly
    Answer: b
  10. Which is organic acid?
    a) HCl
    b) H₂SO₄
    c) Acetic acid
    d) HNO₃
    Answer: c

Here is the continuation (41–100) in the same proper MCQ format (like 1–40) with full options and answers:

41–60

  1. Which acid is present in tomatoes?
    a) Tartaric acid
    b) Oxalic acid
    c) Citric acid
    d) Lactic acid
    Answer: c
  2. Which acid is present in curd?
    a) Acetic acid
    b) Lactic acid
    c) Formic acid
    d) Citric acid
    Answer: b
  3. Which acid is present in ant sting?
    a) Citric acid
    b) Formic acid
    c) Lactic acid
    d) Oxalic acid
    Answer: b
  4. The pH of pure water at 25°C is:
    a) 5
    b) 6
    c) 7
    d) 8
    Answer: c
  5. Which of the following is a basic oxide?
    a) CO₂
    b) SO₂
    c) CaO
    d) NO₂
    Answer: c
  6. Which of the following is an acidic oxide?
    a) MgO
    b) Na₂O
    c) CO₂
    d) CaO
    Answer: c
  7. Which gas turns lime water milky?
    a) O₂
    b) CO₂
    c) H₂
    d) N₂
    Answer: b
  8. What is the nature of Na₂CO₃ solution?
    a) Acidic
    b) Neutral
    c) Basic
    d) Strong acid
    Answer: c
  9. Which substance is used as an antacid?
    a) NaCl
    b) Mg(OH)₂
    c) HCl
    d) CO₂
    Answer: b
  10. Which of the following is a strong base?
    a) NH₄OH
    b) NaOH
    c) CH₃COOH
    d) H₂CO₃
    Answer: b

61–80

  1. Acid reacts with zinc to produce:
    a) Oxygen
    b) Hydrogen
    c) Nitrogen
    d) Carbon dioxide
    Answer: b
  2. Which compound is used in fire extinguishers?
    a) NaCl
    b) NaHCO₃
    c) CaCO₃
    d) KCl
    Answer: b
  3. On heating, baking soda produces:
    a) NaCl
    b) CO₂
    c) H₂
    d) O₂
    Answer: b
  4. Which salt is used in glass manufacturing?
    a) NaCl
    b) Na₂CO₃
    c) NH₄Cl
    d) CaCl₂
    Answer: b
  5. Which salt is acidic in nature?
    a) NaCl
    b) KCl
    c) NH₄Cl
    d) Na₂CO₃
    Answer: c
  6. Which salt is basic in nature?
    a) NH₄Cl
    b) Na₂CO₃
    c) HCl
    d) HNO₃
    Answer: b
  7. Which indicator gives pink color in base?
    a) Litmus
    b) Turmeric
    c) Phenolphthalein
    d) Methyl orange
    Answer: c
  8. Which acid is called oil of vitriol?
    a) HCl
    b) HNO₃
    c) H₂SO₄
    d) CH₃COOH
    Answer: c
  9. Which acid is used in cleaning metals?
    a) HCl
    b) H₂SO₄
    c) CH₃COOH
    d) H₂CO₃
    Answer: a
  10. Which compound removes permanent hardness of water?
    a) Na₂CO₃
    b) HCl
    c) NaCl
    d) CO₂
    Answer: a

61–100

  1. Which gas is evolved when acid reacts with metal carbonate?
    a) H₂
    b) O₂
    c) CO₂
    d) SO₂
    Answer: c
  2. The chemical formula of quick lime is:
    a) CaCO₃
    b) CaO
    c) Ca(OH)₂
    d) CaSO₄
    Answer: b
  3. Which of the following is not an alkali?
    a) NaOH
    b) KOH
    c) NH₄OH
    d) CuO
    Answer: d
  4. Acidic solutions have pH:
    a) Less than 7
    b) Equal to 7
    c) Greater than 7
    d) Equal to 14
    Answer: a
  5. Basic solutions have pH:
    a) Less than 7
    b) Equal to 7
    c) Greater than 7
    d) Equal to 1
    Answer: c
  6. The reaction between Ca(OH)₂ and CO₂ forms:
    a) CaCO₃
    b) CaCl₂
    c) Na₂CO₃
    d) HCl
    Answer: a
  7. Which compound contains water of crystallization?
    a) NaCl
    b) CuSO₄·5H₂O
    c) HCl
    d) NaOH
    Answer: b
  8. On heating hydrated copper sulphate, its color changes from:
    a) Blue to white
    b) White to blue
    c) Red to blue
    d) Green to white
    Answer: a
  9. Which acid is found in vinegar?
    a) Citric acid
    b) Acetic acid
    c) Formic acid
    d) Oxalic acid
    Answer: b
  10. Soil with low pH is treated with:
    a) Acid
    b) Base
    c) Lime
    d) Salt
    Answer: c
  11. Which acid is present in orange?
    a) Citric acid
    b) Lactic acid
    c) Tartaric acid
    d) Formic acid
    Answer: a
  12. The pH scale ranges from:
    a) 1–10
    b) 0–14
    c) 0–7
    d) 7–14
    Answer: b
  13. Which acid is used in manufacture of fertilizers?
    a) HNO₃
    b) CH₃COOH
    c) H₂CO₃
    d) HCl
    Answer: a
  14. Which of the following is neutral?
    a) HCl
    b) NaOH
    c) NaCl
    d) NH₄Cl
    Answer: c
  15. Which indicator shows different colors for different pH values?
    a) Litmus
    b) Phenolphthalein
    c) Universal indicator
    d) Turmeric
    Answer: c
  16. CaSO₄·½H₂O is:
    a) Gypsum
    b) Plaster of Paris
    c) Washing soda
    d) Baking soda
    Answer: b
  17. Which gas is released during neutralization?
    a) CO₂
    b) H₂
    c) No gas
    d) O₂
    Answer: c
  18. The solution of NH₄OH is:
    a) Strong acid
    b) Weak base
    c) Strong base
    d) Neutral
    Answer: b
  19. Which acid is called aqua fortis?
    a) HCl
    b) H₂SO₄
    c) HNO₃
    d) CH₃COOH
    Answer: c
  20. Which compound is formed when POP reacts with water?
    a) CaCO₃
    b) CaSO₄·2H₂O
    c) NaCl
    d) CaO
    Answer: b

81–100

  1. Which of the following acids is dibasic?
    a) HCl
    b) HNO₃
    c) H₂SO₄
    d) CH₃COOH
    Answer: c
  2. Which of the following bases is weak?
    a) NaOH
    b) KOH
    c) NH₄OH
    d) Ca(OH)₂
    Answer: c
  3. Which salt is formed from strong acid and strong base?
    a) NH₄Cl
    b) NaCl
    c) Na₂CO₃
    d) NH₄NO₃
    Answer: b
  4. Which of the following is used to test acidity of soil?
    a) Litmus
    b) Universal indicator
    c) Phenolphthalein
    d) Turmeric
    Answer: b
  5. Which compound is used for whitewashing?
    a) CaO
    b) Ca(OH)₂
    c) CaCO₃
    d) Na₂CO₃
    Answer: b
  6. Which acid is present in tamarind?
    a) Lactic acid
    b) Tartaric acid
    c) Citric acid
    d) Formic acid
    Answer: b
  7. The pH of a strong base is usually:
    a) 1–3
    b) 4–6
    c) 7
    d) 12–14
    Answer: d
  8. Which of the following is amphoteric in nature?
    a) NaOH
    b) HCl
    c) Al(OH)₃
    d) CO₂
    Answer: c
  9. Which salt is used in baking powder?
    a) Na₂CO₃
    b) NaHCO₃
    c) NH₄Cl
    d) CaCl₂
    Answer: b
  10. Which compound is responsible for hardness of water?
    a) Sodium salts
    b) Potassium salts
    c) Calcium and magnesium salts
    d) Chlorine
    Answer: c
  11. Which gas is evolved when zinc reacts with dilute HCl?
    a) O₂
    b) CO₂
    c) H₂
    d) N₂
    Answer: c
  12. Which acid is present in apples?
    a) Citric acid
    b) Malic acid
    c) Lactic acid
    d) Tartaric acid
    Answer: b
  13. Which compound is formed when quick lime reacts with water?
    a) CaCO₃
    b) Ca(OH)₂
    c) CaSO₄
    d) NaOH
    Answer: b
  14. The nature of NH₄Cl solution is:
    a) Basic
    b) Neutral
    c) Acidic
    d) Strong base
    Answer: c
  15. Which acid is used in soft drinks?
    a) Acetic acid
    b) Carbonic acid
    c) Hydrochloric acid
    d) Sulphuric acid
    Answer: b
  16. The chemical formula of slaked lime is:
    a) CaO
    b) Ca(OH)₂
    c) CaCO₃
    d) CaSO₄
    Answer: b
  17. Which salt is formed from weak acid and strong base?
    a) Na₂CO₃
    b) NH₄Cl
    c) NaCl
    d) HCl
    Answer: a
  18. Which acid is present in grapes?
    a) Citric acid
    b) Lactic acid
    c) Tartaric acid
    d) Formic acid
    Answer: c
  19. The pH of blood is approximately:
    a) 5.5
    b) 6.0
    c) 7.4
    d) 8.5
    Answer: c
  20. Which salt is formed when HCl reacts with NaOH?
    a) Na₂CO₃
    b) NaCl
    c) NH₄Cl
    d) NaHCO₃
    Answer: b

1–100 Very Short Answer Questions with Answers

1. What is an acid?
An acid is a substance that produces hydrogen ions (H⁺) in aqueous solution.

2. What is a base?
A base is a substance that produces hydroxide ions (OH⁻) in aqueous solution.

3. What is an alkali?
An alkali is a water-soluble base that produces OH⁻ ions in solution.

4. Define salt.
A salt is a compound formed by neutralization reaction between an acid and a base.

5. What is neutralization?
It is a reaction between an acid and a base producing salt and water.

6. What is pH scale?
pH scale measures acidity or basicity of a solution from 0 to 14.

7. What does pH 7 indicate?
pH 7 indicates a neutral solution.

8. Name a strong acid.
Hydrochloric acid (HCl) is a strong acid.

9. Name a weak acid.
Acetic acid is a weak acid.

10. Name a strong base.
Sodium hydroxide is a strong base.

11. Name a weak base.
Ammonium hydroxide is a weak base.

12. What is litmus solution?
Litmus is a natural indicator obtained from lichens.

13. Effect of acid on blue litmus?
Acid turns blue litmus red.

14. Effect of base on red litmus?
Base turns red litmus blue.

15. What is phenolphthalein in acid?
It remains colorless in acidic solution.

16. What is phenolphthalein in base?
It turns pink in basic solution.

17. What is methyl orange in acid?
It turns red in acidic solution.

18. What is methyl orange in base?
It turns yellow in basic solution.

19. Which gas evolves when acid reacts with metal?
Hydrogen gas evolves.

20. What happens when acid reacts with carbonate?
Carbon dioxide gas is produced along with salt and water.

21. Name a natural indicator.
Turmeric is a natural indicator.

22. What happens to turmeric in base?
It turns reddish-brown in basic solution.

23. What is universal indicator?
It is a mixture of indicators showing different colors at different pH values.

24. What is tooth decay caused by?
It is caused by acids produced by bacteria in mouth.

25. What is antacid?
Antacid is a mild base used to neutralize excess stomach acid.

26. Name a common antacid.
Magnesium hydroxide is a common antacid.

27. What is baking soda?
Baking soda is sodium hydrogen carbonate (NaHCO₃).

28. What is washing soda?
Washing soda is sodium carbonate decahydrate.

29. Chemical formula of bleaching powder?
CaOCl₂.

30. How is bleaching powder prepared?
By passing chlorine gas over dry slaked lime.

31. Chemical formula of plaster of Paris?
CaSO₄·½H₂O.

32. How is plaster of Paris prepared?
By heating gypsum at 100–120°C.

33. What is gypsum?
Calcium sulfate dihydrate (CaSO₄·2H₂O).

34. What happens when POP reacts with water?
It forms gypsum and sets into hard solid mass.

35. Define strong acid.
An acid that completely ionizes in water.

36. Define weak acid.
An acid that partially ionizes in water.

37. Define strong base.
A base that completely dissociates in water.

38. Define weak base.
A base that partially dissociates in water.

39. What is concentration?
Amount of solute present in given volume of solution.

40. What is dilution?
Process of adding water to decrease concentration of solution.

41. Why is water added to acid slowly?
To prevent splashing due to heat released.

42. What is exothermic reaction?
A reaction that releases heat.

43. Nature of metal oxides?
Most metal oxides are basic in nature.

44. Nature of non-metal oxides?
Most non-metal oxides are acidic in nature.

45. What is acid rain?
Rain containing acids like sulfuric and nitric acid.

46. What is formed when acid reacts with base?
Salt and water are formed.

47. pH of strong acid?
Less than 3.

48. pH of strong base?
Greater than 11.

49. What are indicators?
Substances that change color in acidic or basic solutions.

50. What is hydrochloric acid present in?
It is present in stomach.

51. What is milk of magnesia?
Suspension of magnesium hydroxide in water.

52. What is common salt?
Sodium chloride (NaCl).

53. What is basic solution?
Solution having pH more than 7.

54. What is acidic solution?
Solution having pH less than 7.

55. What happens when base reacts with non-metal oxide?
Salt and water are formed.

56. What is chemical name of baking soda?
Sodium hydrogen carbonate.

57. Use of baking soda in cooking?
Used as leavening agent in baking.

58. What is baking powder?
Mixture of baking soda and weak acid.

59. Why is POP stored in moisture-proof containers?
Because it reacts with moisture and hardens.

60. What is salt of strong acid and strong base?
Neutral salt.

61. Example of neutral salt?
Sodium chloride.

62. Example of acidic salt?
Ammonium chloride.

63. Example of basic salt?
Sodium carbonate.

64. What is soil treatment for acidic soil?
Adding quicklime or slaked lime.

65. What is soil treatment for basic soil?
Adding organic matter.

66. What is pH of distilled water?
7.

67. What happens to pH on dilution of acid?
pH increases.

68. What happens to pH on dilution of base?
pH decreases.

69. What is corrosion?
Gradual destruction of metals by reaction with environment.

70. What is rust?
Hydrated iron(III) oxide.

71. What is hydrated salt?
Salt containing water of crystallization.

72. Example of hydrated salt?
Washing soda.

73. What is water of crystallization?
Fixed number of water molecules in a salt crystal.

74. Why do acids conduct electricity?
Because they produce ions in solution.

75. Why do dry HCl gas not show acidity?
Because it does not produce H⁺ ions without water.

76. What is indicator used in titration?
Phenolphthalein or methyl orange.

77. What is universal solvent?
Water.

78. What is caustic soda?
Sodium hydroxide.

79. What is caustic potash?
Potassium hydroxide.

80. What is lime water?
Aqueous solution of calcium hydroxide.

81. What gas turns lime water milky?
Carbon dioxide.

82. What is formed when CO₂ reacts with lime water?
Calcium carbonate.

83. What happens on passing excess CO₂?
Milkiness disappears due to calcium bicarbonate formation.

84. What is strong electrolyte?
Substance that completely ionizes in water.

85. What is weak electrolyte?
Substance that partially ionizes in water.

86. What is acidity of soil measured by?
pH value.

87. What is alkali metal hydroxide nature?
Strongly basic.

88. What is amphoteric oxide?
Oxide reacting with both acids and bases.

89. Example of amphoteric oxide?
Aluminum oxide.

90. What is salt hydrolysis?
Reaction of salt with water to form acidic or basic solution.

91. What is indicator color at pH 1?
Red.

92. What is indicator color at pH 14?
Violet or dark blue.

93. What is formed when acid reacts with metal oxide?
Salt and water.

94. Why are acids sour?
Due to presence of hydrogen ions.

95. Why are bases bitter?
Due to hydroxide ions.

96. What is chemical name of slaked lime?
Calcium hydroxide.

97. What is quicklime?
Calcium oxide.

98. What is formed when quicklime reacts with water?
Slaked lime and heat.

99. What is strength of acid determined by?
Its degree of ionization.

100. What is the nature of soap solution?
Basic in nature.

Here are Short Answer Questions

1. What are acids? Give examples.

Acids are substances that produce hydrogen ions (H⁺) when dissolved in water. They have sour taste and turn blue litmus red. Examples include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃), and acetic acid (CH₃COOH).

2. What are bases? Give examples.

Bases are substances that produce hydroxide ions (OH⁻) in aqueous solution. They taste bitter and turn red litmus blue. Examples include sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide [Ca(OH)₂], and ammonium hydroxide (NH₄OH).

3. What is an alkali?

An alkali is a base that is soluble in water and produces hydroxide ions in solution. All alkalis are bases, but all bases are not alkalis. Examples include sodium hydroxide and potassium hydroxide.

4. Define salt with examples.

A salt is a compound formed when the hydrogen ion of an acid is replaced by a metal or ammonium ion. It is generally produced by neutralization. Examples include sodium chloride (NaCl), potassium nitrate (KNO₃), and ammonium sulfate ((NH₄)₂SO₄).

5. What is neutralization reaction?

Neutralization is a chemical reaction between an acid and a base that produces salt and water. For example:
HCl + NaOH → NaCl + H₂O.
It reduces acidity or basicity of a solution.

6. What is pH scale?

The pH scale measures the acidity or basicity of a solution. It ranges from 0 to 14. A pH less than 7 indicates acidic nature, 7 is neutral, and more than 7 indicates basic nature.

7. What are indicators?

Indicators are substances that change color in acidic or basic solutions. They help determine the nature of a solution. Examples include litmus, phenolphthalein, methyl orange, turmeric, and universal indicator.

8. Explain the action of litmus.

Litmus is a natural indicator extracted from lichens. It turns red in acidic solution and blue in basic solution. It remains purple in neutral solution. It is commonly used in laboratories to test acids and bases.

9. What is universal indicator?

Universal indicator is a mixture of several indicators that gives different colors at different pH values. It helps determine approximate pH of a solution by comparing its color with a standard pH color chart.

10. What happens when acid reacts with metal?

When acids react with metals, hydrogen gas is released and a salt is formed. Example:
Zn + 2HCl → ZnCl₂ + H₂.
This reaction is used to identify acids.

11. What happens when acid reacts with metal carbonate?

When an acid reacts with a metal carbonate, it forms salt, water, and carbon dioxide gas. Example:
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂.

12. What is tooth decay and its relation with pH?

Tooth decay occurs when bacteria produce acids that lower the pH below 5.5. This damages tooth enamel. Using toothpaste (basic in nature) helps neutralize acids and protect teeth.

13. What are strong and weak acids?

Strong acids completely ionize in water, producing large amounts of H⁺ ions. Weak acids partially ionize. Example: HCl is strong, while acetic acid is weak.

14. What are strong and weak bases?

Strong bases completely dissociate in water to produce OH⁻ ions, such as NaOH. Weak bases partially dissociate, like ammonium hydroxide. Strength depends on degree of ionization.

15. What is dilution?

Dilution is the process of reducing concentration of a solution by adding water. During dilution of acids, acid must be added slowly to water to prevent splashing due to heat release.

16. Why are acids not acidic in dry state?

Acids show acidic properties only in aqueous solution because they produce hydrogen ions only in presence of water. Dry HCl gas does not show acidity without water.

17. What is baking soda?

Baking soda is sodium hydrogen carbonate (NaHCO₃). It is a mild base used in baking, fire extinguishers, and as an antacid. It releases carbon dioxide when heated or reacted with acid.

18. What is washing soda?

Washing soda is sodium carbonate decahydrate (Na₂CO₃·10H₂O). It is used in cleaning, softening hard water, and manufacturing glass and soap.

19. What is bleaching powder?

Bleaching powder (CaOCl₂) is prepared by passing chlorine gas over dry slaked lime. It is used for bleaching cotton and linen, disinfecting drinking water, and as an oxidizing agent.

20. What is plaster of Paris?

Plaster of Paris (CaSO₄·½H₂O) is prepared by heating gypsum. It is used to make statues, casts, toys, and decorative items. It sets quickly when mixed with water.

21. What is gypsum?

Gypsum is calcium sulfate dihydrate (CaSO₄·2H₂O). It is a naturally occurring mineral used in making plaster of Paris and cement. When heated, it loses water molecules and forms plaster of Paris.

22. What is water of crystallization?

Water of crystallization is the fixed number of water molecules chemically combined with a salt in crystalline form. It gives the salt its shape and properties. Example: CuSO₄·5H₂O.

23. What is acid rain?

Acid rain contains sulfuric and nitric acids formed from sulfur dioxide and nitrogen oxides in the atmosphere. It damages buildings, soil, crops, and aquatic life.

24. What are amphoteric oxides?

Amphoteric oxides react with both acids and bases to form salt and water. Examples include aluminum oxide (Al₂O₃) and zinc oxide (ZnO).

25. Why do acids conduct electricity?

Acids conduct electricity because they ionize in water to produce mobile hydrogen ions. These ions carry electric current through the solution.

26. Why are bases bitter?

Bases taste bitter and feel soapy due to presence of hydroxide ions. They turn red litmus blue and neutralize acids.

27. What is corrosion?

Corrosion is gradual destruction of metals due to reaction with environment. Rusting of iron is common example.

28. What is rust?

Rust is hydrated iron(III) oxide formed when iron reacts with oxygen and moisture.

29. What is soil pH importance?

Soil pH affects plant growth. Acidic soil is treated with lime; basic soil is treated with organic matter.

30. What is common salt?

Common salt is sodium chloride formed by neutralization of HCl and NaOH.

31. What is milk of magnesia?

Milk of magnesia is magnesium hydroxide suspension used as antacid to relieve acidity.

32. What is lime water?

Lime water is aqueous calcium hydroxide solution that turns milky with carbon dioxide.

33. What is exothermic reaction in dilution?

Dilution of acid releases heat, hence it is exothermic reaction.

34. What is concentration of solution?

Concentration is amount of solute dissolved in given volume of solution.

35. What is basic salt?

Basic salt is formed from strong base and weak acid like sodium carbonate.

36. What is acidic salt?

Acidic salt is formed from strong acid and weak base like ammonium chloride.

37. What is neutral salt?

Neutral salt is formed from strong acid and strong base like sodium chloride.

38. Why is POP stored carefully?

POP reacts with moisture forming gypsum and hardens.

39. What happens when CO₂ passed in excess lime water?

Milkiness disappears due to formation of calcium bicarbonate.

40. What is role of baking powder?

Baking powder releases CO₂ gas making cakes soft and spongy.

41. What happens when acids react with metal oxides?

When acids react with metal oxides, salt and water are formed. This shows that metal oxides are basic in nature. For example, copper oxide reacts with hydrochloric acid to form copper chloride and water.

42. What happens when bases react with non-metal oxides?

When bases react with non-metal oxides, salt and water are formed. This shows that non-metal oxides are acidic in nature. For example, calcium hydroxide reacts with carbon dioxide to form calcium carbonate and water.

43. Why are metal oxides basic in nature?

Metal oxides are basic because they react with acids to form salt and water. Many metal oxides dissolve in water to form metal hydroxides, which release hydroxide ions and show basic properties.

44. Why are non-metal oxides acidic in nature?

Non-metal oxides are acidic because they react with bases to produce salt and water. Many non-metal oxides dissolve in water forming acids. For example, sulfur dioxide dissolves in water forming sulfurous acid.

45. What is the role of hydrochloric acid in the stomach?

Hydrochloric acid present in the stomach helps in digestion of food and kills harmful bacteria. However, excess acid may cause indigestion or acidity, which can be relieved by taking antacids.

46. What are antacids? Give examples.

Antacids are mild bases used to neutralize excess stomach acid. They provide relief from acidity and indigestion. Examples include magnesium hydroxide and sodium hydrogen carbonate.

47. Explain the action of phenolphthalein indicator.

Phenolphthalein is a synthetic indicator. It remains colorless in acidic and neutral solutions but turns pink in basic solutions. It is commonly used in acid-base titrations to detect the endpoint.

48. Explain the action of methyl orange indicator.

Methyl orange turns red in acidic solution and yellow in basic solution. In neutral solution, it appears orange. It is widely used as an indicator in laboratory experiments.

49. What does pH less than 7 indicate?

A pH value less than 7 indicates that the solution is acidic in nature. Lower the pH value, stronger is the acid. For example, gastric juice has a pH around 1–2.

50. What does pH greater than 7 indicate?

A pH value greater than 7 indicates that the solution is basic in nature. Higher the pH value, stronger is the base. Soap solution usually has a pH around 9–10.

51. What are strong acids? Give examples.

Strong acids are those acids that completely ionize in aqueous solution, producing large amounts of hydrogen ions. Examples include hydrochloric acid, nitric acid, and sulfuric acid.

52. What are weak acids? Give examples.

Weak acids are those acids that partially ionize in water. They produce fewer hydrogen ions compared to strong acids. Example includes acetic acid and carbonic acid.

53. What are strong bases? Give examples.

Strong bases completely dissociate in water producing hydroxide ions. They are highly corrosive. Examples include sodium hydroxide and potassium hydroxide.

54. What are weak bases? Give examples.

Weak bases partially ionize in water and produce fewer hydroxide ions. Ammonium hydroxide is a common example of a weak base.

55. What is caustic soda?

Caustic soda is the common name for sodium hydroxide (NaOH). It is a strong base used in soap making, paper manufacturing, and textile industries.

56. What is caustic potash?

Caustic potash is potassium hydroxide (KOH). It is a strong base used in manufacturing liquid soaps, fertilizers, and alkaline batteries.

57. What is quicklime?

Quicklime is calcium oxide (CaO). It is prepared by heating limestone. It reacts vigorously with water to form slaked lime and releases heat.

58. What is slaked lime?

Slaked lime is calcium hydroxide [Ca(OH)₂]. It is formed when quicklime reacts with water. It is used in whitewashing, manufacturing bleaching powder, and treating acidic soil.

59. Why does baking soda release carbon dioxide?

Baking soda releases carbon dioxide when heated or when reacted with an acid. This gas makes cakes and bread soft and spongy during baking.

60. How is washing soda useful?

Washing soda is used for cleaning clothes, softening hard water, and in the manufacture of glass, soap, and paper. It also removes permanent hardness of water.

61. What are uses of bleaching powder?

Bleaching powder is used for bleaching cotton and linen, disinfecting drinking water, and as an oxidizing agent in chemical industries.

62. How does plaster of Paris set?

Plaster of Paris reacts with water to form gypsum. During this reaction, heat is released and a hard solid mass is formed, making it useful for making molds and casts.

63. What is the importance of water of crystallization?

Water of crystallization gives specific shape and color to crystalline salts. For example, copper sulfate crystals are blue due to water molecules present.

64. Why is water called universal solvent?

Water is called universal solvent because it dissolves a large number of substances, including many acids, bases, and salts.

65. How does turmeric act as indicator?

Turmeric remains yellow in acidic and neutral solutions but turns reddish brown in basic solutions. Therefore, it is used as a natural indicator.

66. Why does hydrogen gas burn with a pop sound?

Hydrogen gas burns rapidly in presence of oxygen producing water and a characteristic ‘pop’ sound. This test confirms presence of hydrogen gas.

67. What are effects of acid rain?

Acid rain damages monuments, corrodes metals, affects soil fertility, and harms aquatic life. It is mainly caused by sulfur dioxide and nitrogen oxides in atmosphere.

68. How does dilution affect pH of acids?

Dilution of an acid increases its pH value because concentration of hydrogen ions decreases. However, it still remains acidic.

69. How does dilution affect pH of bases?

Dilution of a base decreases its pH value because concentration of hydroxide ions decreases. However, it still remains basic.

70. What is salt hydrolysis?

Salt hydrolysis is the reaction of salt with water to produce acidic or basic solution depending on the nature of acid and base from which it is formed.

71. Why is NaCl solution neutral?

Sodium chloride is formed from strong acid and strong base. It does not affect the pH of water; therefore, its solution is neutral.

72. Why is ammonium chloride acidic?

Ammonium chloride is formed from strong acid and weak base. It releases hydrogen ions in water, making the solution acidic.

73. Why is sodium carbonate basic?

Sodium carbonate is formed from strong base and weak acid. It produces hydroxide ions in water, making the solution basic.

74. Why are acids corrosive?

Acids are corrosive because they react with metals and living tissues, causing damage. Strong acids like sulfuric acid can burn skin.

75. Why are bases caustic?

Strong bases like sodium hydroxide are caustic and can damage skin. They react with oils and proteins in tissues, causing burns.

76. What is the pH of distilled water?

Distilled water has a pH of 7 at room temperature, indicating that it is neutral.

77. Why does tooth enamel dissolve below pH 5.5?

Tooth enamel is made of calcium phosphate. When pH falls below 5.5, acids dissolve this mineral, causing tooth decay.

78. What is concentration of a solution?

Concentration refers to the amount of solute present in a given volume of solution. Higher concentration means more solute particles.

79. Why should acid be added to water?

Acid should be added slowly to water because dilution releases heat. Adding water to acid may cause splashing and burns.

80. What is importance of pH in agriculture?

pH of soil affects nutrient availability to plants. Farmers test soil pH and add lime or organic matter to maintain suitable pH.

81. What is importance of pH in medicine?

pH balance in human body is essential for proper functioning of enzymes and organs. Blood has a slightly basic pH around 7.4.

82. What is effect of CO₂ on lime water?

Carbon dioxide turns lime water milky due to formation of calcium carbonate precipitate.

83. Why does milkiness disappear with excess CO₂?

Excess carbon dioxide converts calcium carbonate into soluble calcium bicarbonate, making the solution clear again.

84. What are mineral acids?

Mineral acids are inorganic acids derived from minerals. Examples include hydrochloric acid, nitric acid, and sulfuric acid.

85. What are organic acids?

Organic acids contain carbon and are usually weak acids. Examples include acetic acid and citric acid.

86. What is role of sulfuric acid in batteries?

Sulfuric acid is used as electrolyte in lead-acid batteries. It helps in flow of electric current during charging and discharging.

87. Why is bleaching powder unstable?

Bleaching powder decomposes on exposure to air and moisture, losing chlorine. Therefore, it is stored in airtight containers.

88. What is role of washing soda in cleaning?

Washing soda removes grease and stains by reacting with fatty acids. It also softens hard water improving cleaning efficiency.

89. Why does copper sulfate lose color on heating?

On heating, copper sulfate loses water of crystallization and turns white. Adding water restores its blue color.

90. What are electrolytes?

Electrolytes are substances that produce ions in solution and conduct electricity. Acids, bases, and salts are electrolytes.

91. Why is ammonia considered base?

Ammonia dissolves in water to form ammonium hydroxide, which releases hydroxide ions. Therefore, it behaves as a weak base.

92. What is acid-base titration?

Acid-base titration is a laboratory method used to determine concentration of acid or base using an indicator.

93. Why are soaps basic?

Soaps are sodium or potassium salts of fatty acids. Their solutions are basic in nature due to hydrolysis.

94. How are salts classified?

Salts are classified as neutral, acidic, or basic depending on strength of acid and base from which they are formed.

95. What is reaction of quicklime with water?

Quicklime reacts vigorously with water forming slaked lime and releasing heat. This reaction is highly exothermic.

96. Why is plaster of Paris useful in casts?

Plaster of Paris sets quickly when mixed with water, forming a hard protective layer, making it suitable for medical casts.

97. What is significance of universal indicator chart?

Universal indicator chart helps determine approximate pH value by matching color of solution with standard pH scale.

98. Why is sodium hydrogen carbonate mild base?

It partially dissociates in water producing small amount of hydroxide ions, making it a weak and mild base.

99. What happens when acid reacts with hydrogen carbonate?

Acid reacts with hydrogen carbonate producing salt, water, and carbon dioxide gas with brisk effervescence.

100. Why are acid-base reactions important in daily life?

Acid-base reactions occur in digestion, agriculture, medicine, cleaning products, and industry. They play vital role in maintaining environmental and biological balance.

Here are Long Answer Questions

1. Explain acids, their properties and chemical reactions.

Acids are substances that produce hydrogen ions (H⁺) in aqueous solution. They have a sour taste and turn blue litmus red. Acids react with metals to produce salt and hydrogen gas. They react with metal carbonates and bicarbonates to produce salt, water, and carbon dioxide. Acids also react with bases in a neutralization reaction forming salt and water. Strong acids like hydrochloric acid completely ionize in water, whereas weak acids like acetic acid partially ionize. Acids conduct electricity in aqueous solution because of free ions. Common mineral acids include hydrochloric acid, sulfuric acid, and nitric acid. Organic acids such as acetic acid and citric acid are usually weak acids. Acids are widely used in industries, batteries, fertilizers, and medicine.

2. Explain bases and their properties.

Bases are substances that produce hydroxide ions (OH⁻) in aqueous solution. They taste bitter, feel slippery, and turn red litmus blue. Bases neutralize acids to form salt and water. Strong bases like sodium hydroxide and potassium hydroxide completely dissociate in water, whereas weak bases such as ammonium hydroxide partially dissociate. Bases react with non-metal oxides to form salt and water, showing their basic nature. Many bases are caustic and can cause burns on skin. Alkalis are bases soluble in water. Bases are used in soap making, cleaning agents, paper manufacturing, and medicine. Their strength depends on the extent of ionization in water.

3. Describe the pH scale and its importance.

The pH scale measures the acidity or basicity of a solution. It ranges from 0 to 14. A pH less than 7 indicates acidity, 7 is neutral, and greater than 7 indicates basicity. Lower pH means stronger acid, and higher pH means stronger base. The pH scale is important in daily life. In agriculture, soil pH affects crop yield. In medicine, blood pH must remain around 7.4 for proper body function. In the environment, acid rain lowers pH of water bodies, affecting aquatic life. Tooth enamel starts dissolving below pH 5.5. Thus, maintaining proper pH balance is essential in many fields.

4. Explain neutralization reaction with examples.

Neutralization is a chemical reaction between an acid and a base producing salt and water. For example, hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water. This reaction reduces acidity or basicity of a solution. Neutralization reactions are useful in daily life. Antacids neutralize excess stomach acid. Farmers add lime to acidic soil to neutralize it. In factories, basic substances are used to neutralize acidic wastes before disposal. These reactions are generally exothermic, meaning heat is released. Neutralization plays a vital role in maintaining environmental and biological balance.

5. Explain strong and weak acids and bases.

Strong acids completely ionize in water, producing large amounts of hydrogen ions. Examples include hydrochloric acid and sulfuric acid. Weak acids partially ionize, such as acetic acid. Similarly, strong bases like sodium hydroxide completely dissociate to produce hydroxide ions, while weak bases like ammonium hydroxide partially dissociate. The strength of an acid or base depends on its degree of ionization, not its concentration. Strong acids and bases are highly corrosive and reactive. Weak acids and bases are less harmful and commonly found in daily life, such as vinegar and ammonia solution.

6. Explain the preparation and uses of bleaching powder.

Bleaching powder (CaOCl₂) is prepared by passing chlorine gas over dry slaked lime. It is a pale yellow powder with a strong smell of chlorine. It is used for bleaching cotton, linen, and wood pulp in textile and paper industries. It is also used to disinfect drinking water and swimming pools. Bleaching powder acts as an oxidizing agent and is used in chemical industries. It should be stored in airtight containers because it decomposes in presence of moisture and air, losing its effectiveness. Its disinfecting property makes it very important in sanitation.

7. Describe plaster of Paris and its uses.

Plaster of Paris (CaSO₄·½H₂O) is prepared by heating gypsum (CaSO₄·2H₂O) at about 100–120°C. It is a white powder that sets quickly when mixed with water. On adding water, it forms gypsum again and releases heat. It is used in making statues, toys, decorative materials, and medical casts for fractured bones. It is also used in making molds and blackboard chalk. It must be stored in moisture-proof containers because it reacts with moisture and hardens. Its quick-setting property makes it very useful in various industries.

8. Explain washing soda and its applications.

Washing soda (Na₂CO₃·10H₂O) is sodium carbonate decahydrate. It is prepared by heating baking soda. Washing soda is used in cleaning agents and softening hard water. It removes permanent hardness by precipitating calcium and magnesium salts. It is used in glass, soap, and paper industries. Washing soda is also used in manufacturing sodium compounds. It contains water of crystallization, which gives it crystalline structure. It plays an important role in household and industrial cleaning processes.

9. Describe baking soda and its uses.

Baking soda (NaHCO₃) is sodium hydrogen carbonate. It is a mild base used in baking powder. When heated or mixed with acid, it releases carbon dioxide gas, making cakes and bread soft and spongy. It is also used as an antacid to relieve acidity. Baking soda is used in fire extinguishers because it releases carbon dioxide, which helps in extinguishing fire. It is also used in soda-acid fire extinguishers and cleaning agents.

10. Explain acid rain and its effects.

Acid rain is caused by sulfur dioxide and nitrogen oxides released from industries and vehicles. These gases react with water vapor forming sulfuric and nitric acids. Acid rain damages monuments, buildings, crops, and forests. It reduces soil fertility and affects aquatic life by lowering pH of water bodies. Marble structures like historical monuments are especially affected. Acid rain also corrodes metals and paints. Controlling air pollution and using cleaner fuels can reduce acid rain

11. Explain water of crystallization with example.

Water of crystallization refers to fixed number of water molecules chemically combined with a salt in its crystalline form. It gives the salt its definite shape and color. For example, copper sulfate contains five water molecules (CuSO₄·5H₂O) and appears blue in color. When heated, it loses water molecules and turns white. On adding water again, it regains its blue color. Water of crystallization plays an important role in maintaining the structure and physical properties of many salts.

12. Explain the importance of pH in daily life.

The pH scale plays an important role in daily life. In human body, blood maintains a pH around 7.4 for proper functioning. Tooth enamel starts dissolving below pH 5.5. Soil pH affects plant growth and crop yield. Acid rain lowers pH of water bodies affecting aquatic life. In industries, pH control is essential in chemical processes. Thus, maintaining proper pH balance is essential in health, agriculture, and environment.

Here are 50 Assertion–Reason Questions with Answers from Acids, Bases and Salts.

Directions:
A. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
C. Assertion is true, but Reason is false.
D. Assertion is false, but Reason is true.

1

Assertion (A): Acids turn blue litmus red.
Reason (R): Acids produce hydrogen ions in aqueous solution.
Answer: A

2

A: Bases turn red litmus blue.
R: Bases produce hydroxide ions in water.
Answer: A

3

A: Dry HCl gas does not change color of dry litmus paper.
R: Acids produce H⁺ ions only in aqueous solution.
Answer: A

4

A: Sodium hydroxide is a strong base.
R: It completely dissociates in water.
Answer: A

5

A: Acetic acid is a weak acid.
R: It partially ionizes in water.
Answer: A

6

A: All bases are alkalis.
R: Alkalis are water-soluble bases.
Answer: D

7

A: Neutralization produces salt and water.
R: It is reaction between acid and base.
Answer: A

8

A: pH of acidic solution is less than 7.
R: Acidic solutions have excess H⁺ ions.
Answer: A

9

A: pH of basic solution is greater than 7.
R: Basic solutions contain OH⁻ ions.
Answer: A

10

A: Metal oxides are basic in nature.
R: They react with acids to form salt and water.
Answer: A

11

A: Non-metal oxides are acidic in nature.
R: They react with bases to form salt and water.
Answer: A

12

A: Bleaching powder is used to disinfect water.
R: It releases chlorine gas.
Answer: A

13

A: Plaster of Paris sets on adding water.
R: It forms gypsum again.
Answer: A

14

A: Washing soda is used to soften hard water.
R: It removes calcium and magnesium salts.
Answer: A

15

A: Baking soda is used in fire extinguishers.
R: It releases carbon dioxide gas.
Answer: A

16

A: Strong acids are highly corrosive.
R: They completely ionize in water.
Answer: A

17

A: Antacids are basic in nature.
R: They neutralize excess stomach acid.
Answer: A

18

A: Tooth enamel dissolves below pH 5.5.
R: Acids damage calcium phosphate in teeth.
Answer: A

19

A: Acid rain damages monuments.
R: It contains sulfuric and nitric acids.
Answer: A

20

A: Copper sulfate crystals are blue.
R: They contain water of crystallization.
Answer: A

21

A: Sodium chloride solution is neutral.
R: It is formed from strong acid and strong base.
Answer: A

22

A: Ammonium chloride solution is acidic.
R: It is formed from strong acid and weak base.
Answer: A

23

A: Sodium carbonate solution is basic.
R: It is formed from strong base and weak acid.
Answer: A

24

A: Dilution of acid increases pH.
R: Concentration of hydrogen ions decreases.
Answer: A

25

A: Dilution of base decreases pH.
R: Concentration of hydroxide ions decreases.
Answer: A

26

A: Hydrogen gas burns with pop sound.
R: Hydrogen reacts explosively with oxygen.
Answer: A

27

A: Indicators help identify nature of solution.
R: They change color in acidic or basic medium.
Answer: A

28

A: Universal indicator gives different colors at different pH.
R: It is mixture of several indicators.
Answer: A

29

A: Quicklime reacts vigorously with water.
R: The reaction is highly exothermic.
Answer: A

30

A: POP should be stored in moisture-proof container.
R: It reacts with moisture and hardens.
Answer: A

31

A: Acids conduct electricity.
R: They produce ions in aqueous solution.
Answer: A

32

A: Bases feel slippery.
R: They react with oils in skin.
Answer: B

33

A: Soil pH affects crop yield.
R: Nutrient availability depends on pH.
Answer: A

34

A: Carbon dioxide turns lime water milky.
R: Calcium carbonate is formed.
Answer: A

35

A: Excess CO₂ clears lime water.
R: Calcium bicarbonate is formed.
Answer: A

36

A: Mineral acids are inorganic acids.
R: They are derived from minerals.
Answer: A

37

A: Organic acids are generally weak.
R: They partially ionize in water.
Answer: A

38

A: Sodium hydroxide is called caustic soda.
R: It is a strong base.
Answer: B

39

A: Sulfuric acid is used in car batteries.
R: It acts as electrolyte.
Answer: A

40

A: Bleaching powder loses chlorine on exposure to air.
R: It decomposes in presence of moisture.
Answer: A

41

A: Gypsum contains two water molecules.
R: It is CaSO₄·2H₂O.
Answer: A

42

A: Baking powder contains baking soda and acid.
R: It helps release carbon dioxide in baking.
Answer: A

43

A: All salts are neutral.
R: Salts may be acidic, basic or neutral.
Answer: D

44

A: Strong electrolytes completely ionize.
R: They produce more ions in solution.
Answer: A

45

A: Ammonia is a base.
R: It produces hydroxide ions in water.
Answer: A

46

A: Acid + carbonate → salt + water + CO₂.
R: Carbon dioxide is released in such reactions.
Answer: A

47

A: Water is called universal solvent.
R: It dissolves many substances.
Answer: A

48

A: Corrosion is chemical deterioration of metal.
R: It occurs due to reaction with environment.
Answer: A

49

A: Rust is hydrated iron(III) oxide.
R: It forms when iron reacts with oxygen and moisture.
Answer: A

50

A: Acid-base reactions are important in daily life.
R: They occur in digestion, agriculture and industries.
Answer: A

Here is a Sample Question Paper (80 Marks)
Chapter: Acids, Bases and Salts
Time: 3 Hours | Maximum Marks: 80

📝 SAMPLE QUESTION PAPER – 80 MARKS

Section A (1 × 20 = 20 Marks)

Very Short Answer Questions
(Attempt all questions. Each question carries 1 mark.)

  1. Define acid.
  2. What is an alkali?
  3. Write the pH of neutral solution.
  4. Name one strong acid.
  5. Name one weak base.
  6. What happens to blue litmus in acid?
  7. What gas is produced when acid reacts with metal?
  8. Write chemical formula of baking soda.
  9. What is bleaching powder used for?
  10. Define neutralization.
  11. Write formula of plaster of Paris.
  12. What is water of crystallization?
  13. Name the indicator that turns pink in base.
  14. What is quicklime?
  15. Define salt.
  16. What is pH of basic solution?
  17. Name one amphoteric oxide.
  18. What is acid rain?
  19. Name a natural indicator.
  20. What is corrosion?

Section B (2 × 6 = 12 Marks)

Short Answer Type Questions (30–40 words)
(Attempt all questions.)

  1. Differentiate between strong acid and weak acid.
  2. Write two properties of bases.
  3. What happens when acid reacts with metal carbonate?
  4. Explain dilution of acid safely.
  5. Write two uses of washing soda.
  6. What is the importance of pH in agriculture?

Section C (3 × 8 = 24 Marks)

Short Answer Type Questions (50–70 words)
(Attempt any 8 questions.)

  1. Explain neutralization reaction with example.
  2. Describe properties of acids.
  3. Describe properties of bases.
  4. What is bleaching powder? Write preparation and one use.
  5. Explain formation and uses of plaster of Paris.
  6. What is baking soda? Mention its uses.
  7. Explain action of universal indicator.
  8. Why are metal oxides basic and non-metal oxides acidic?
  9. Explain salt hydrolysis with example.
  10. What is acid rain? Mention two harmful effects.

Section D (4 × 6 = 24 Marks)

Long Answer Type Questions (120–150 words)
(Attempt any 6 questions.)

  1. Explain pH scale and its importance in daily life.
  2. Describe strong and weak acids and bases with examples.
  3. Explain water of crystallization with suitable example.
  4. Discuss preparation, properties and uses of bleaching powder.
  5. Discuss preparation and uses of washing soda.
  6. Explain reactions of acids with metals, bases and carbonates.
  7. Describe classification of salts with examples.
  8. Explain importance of acids, bases and salts in everyday life.

🔵 Blueprint of Question Paper

SectionType of QuestionsNo. of QuestionsMarks
AVery Short (1 mark)2020
BShort (2 marks)612
CShort (3 marks)824
DLong (4 marks)624
Total80

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