Practice Questions for Science Class 10th "Acids, Bases, and Salts"

Multiple Choice Questions (MCQs):

1. C) Slippery to touch - This is a characteristic of bases, not acids.
2. C) Neutral - A pH of 7 indicates a neutral solution.
3. B) Sodium hydroxide - NaOH is a strong base, fully dissociating in water.
4. A) Acid + Base → Salt + Water - This is the general equation for neutralization.
5. A) NaCl - Common salt or sodium chloride's chemical formula.
6. C) Hydrogen - Reaction of acids with metals generally produces hydrogen gas.
7. C) 0 to 14 - The pH scale typically ranges from 0 to 14.
8. B) Red - Methyl orange turns red in acidic solutions.
9. C) Calcium hydroxide - Calcium hydroxide is a base, not a salt.
10. A) Calcium hypochlorite - Bleaching powder is Ca(OCl)₂.
11. B) Neutralization - Acid and base react to form salt and water.
12. A) Lime water - Lime water turns milky in the presence of CO₂.
13. C) 7 - Pure water is neutral with a pH of 7 at 25°C.
14. C) Sulfuric acid - H₂SO₄ is traditionally called oil of vitriol.
15. B) Carbon dioxide - The reaction produces CO₂, causing effervescence.
16. B) Sodium carbonate - Washing soda is Na₂CO₃·10H₂O.
17. B) Base - Bases turn red litmus blue.
18. B) CaSO₄·½H₂O - Plaster of Paris formula.
19. D) Sodium carbonate - Na₂CO₃ is used in glass manufacturing.
20. B) Gypsum - Calcium sulfate dihydrate, CaSO₄·2H₂O.

Short Answer Questions:

21. Definition of pH:

• pH is a measure of the acidity or basicity of an aqueous solution, defined as the negative logarithm of the hydrogen ion concentration. It's measured using pH meters, litmus paper, or other indicators.

22. Strong Acid vs. Weak Acid:

• Strong Acid: Completely dissociates in water, like HCl.
• Weak Acid: Partially dissociates, like acetic acid (CH₃COOH).

23. Neutralization Process:

• Example: HCl + NaOH → NaCl + H₂O. It involves an acid reacting with a base to form salt and water, reducing the pH to around 7.

24. Acid and Metal Reaction:

• Example: Zn + 2HCl → ZnCl₂ + H₂. Acids react with metals to liberate hydrogen gas.

25. Indicators:

• Indicators show whether a substance is acidic or basic. Examples include litmus (natural) and phenolphthalein (synthetic).

26. Low pH of Lemon Juice:

• Due to the presence of citric acid, which makes lemon juice acidic.

27. Role of Antacids:

• Neutralize stomach acid to relieve indigestion or heartburn.

28. Acid-Base Reaction to Form Salt:

• H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. Acid and base react to form sodium sulfate and water.

29. Importance of pH in Daily Life:

• Affects plant growth, human health (e.g., stomach pH), environmental conditions (e.g., water quality), and industrial processes.

30. Preparing Common Salt:

• Evaporation of seawater or chemical reaction between sodium metal and chlorine gas in the lab.

31. Bases as Alkalis:

• Bases that dissolve in water are called alkalis because they produce hydroxide ions (OH⁻) in solution.

32. Acid and Carbonate Reaction:

• General equation: Acid + Carbonate → Salt + Water + Carbon dioxide. Example: 2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂.

33. Bleaching Powder Preparation:

• Reacting slaked lime (Ca(OH)₂) with chlorine gas. Uses include disinfectant, bleaching agent for textiles, and water treatment.

34. Hydrated vs. Anhydrous Salts:

• Hydrated: Contains water of crystallization, e.g., CuSO₄·5H₂O (blue).
• Anhydrous: Without water, e.g., CuSO₄ (white).

35. Water of Crystallization:

• Water molecules chemically bonded within the crystal structure of a salt. Example: Copper sulfate pentahydrate (CuSO₄·5H₂O).

36. pH and Plant Growth:

• Different plants thrive at different pH levels; acidic or alkaline soil can affect nutrient availability.

37. Uses of Sodium Hydroxide:

• In soap and paper manufacturing, for pH regulation in water treatment, and in the production of various chemicals.

38. Testing for Acid with Litmus:

• Dip blue litmus paper in the solution; if it turns red, the solution is acidic.

39. Acids and Bases as Electrolytes:

• Both acids and bases dissociate into ions in solution, allowing them to conduct electricity.

40. Baking Soda:

• Sodium bicarbonate, NaHCO₃.

Long Answer Questions:

41. Properties of Acids and Bases:

• Acids: Sour taste, turn blue litmus red, pH less than 7, react with metals to liberate hydrogen, and with bases to form salts.
• Bases: Bitter taste, slippery feel, turn red litmus blue, pH greater than 7, react with acids to form salts.

42. Concept of pH:

• pH indicates hydrogen ion concentration; lower pH means higher [H⁺], thus more acidic. The logarithmic nature means each unit change represents a tenfold change in [H⁺].

43. Preparation of Salts:

• NaCl: Neutralization of HCl with NaOH or evaporation of seawater.
• Na₂SO₄: Reacting sulfuric acid with sodium hydroxide.
• CuSO₄: Reacting copper oxide with sulfuric acid.

44. Applications in Daily Life:

• Acids: Vinegar (acetic acid) for cleaning, citric acid in food preservation.
• Bases: Sodium bicarbonate for baking, ammonia for cleaning.

45. Acid Rain:

• Causes: Emissions of SO₂ and NOₓ from industries and vehicles.
• Effects: Damages buildings, affects aquatic ecosystems, reduces soil fertility.

46. Strong vs. Weak Bases:

• Strong: Complete dissociation, e.g., NaOH.
• Weak: Partial dissociation, e.g., NH₄OH.

47. Acids in Human Body:

• Hydrochloric acid in the stomach aids in digestion by activating pepsin and killing bacteria.

48. Plaster of Paris from Gypsum:

• Gypsum (CaSO₄·2H₂O) is heated to lose 3/4 of its water to form Plaster of Paris (CaSO₄·½H₂O). Used for making casts, sculptures, etc.

49. Acids and Bases in Industry:

• Acids: Used in metal processing, fertilizer production, petroleum refining.
• Bases: Soap making, paper manufacturing, water treatment.

50. Water of Crystallization:

• Affects the physical properties of salts like colour, solubility, and crystal structure. Example: Hydrated copper sulphate is blue, anhydrous is white.

51. Logarithmic pH Scale:

• Each pH unit represents a tenfold change in [H⁺] concentration. A pH of 4 is 10 times more acidic than a pH of 5.

52. Soil pH Control:

• Acidic: Lime (calcium carbonate) to raise pH.
• Basic: Sulphur or aluminium sulphate to lower pH.

53. Acid-Base-Salt Interactions:

• Acids react with bases to neutralize, forming salts. Salts can dissociate in water to form acidic or basic solutions.

54. Neutralization in Indigestion:

• Antacids (bases like Mg(OH)₂ or CaCO₃) neutralize excess stomach acid, providing relief.

55. Health Effects of Acids/Bases:

• Acids: Can burn skin, respiratory issues, tooth erosion.
• Bases: Skin and eye irritation, respiratory problems.

56. Chemical Nature of Antacids:

• Often metal hydroxides or carbonates, like Al(OH)₃ or NaHCO₃, which neutralize stomach acid.

57. Ecological Consequences of Industrial Acid Use:

• Acidification of water bodies, soil degradation, and air pollution leading to ecological imbalance.

58. pH and Aquatic Life:

• pH affects the solubility of nutrients and toxins, impacting fish and other aquatic organisms' health and survival.

59. Historical Development of pH Scale:

• Soren Sørensen introduced the pH scale in 1909. Its significance lies in providing a universal measure for acidity/basicity.

60. Altering pH:

• Adding acid decreases pH (increases [H⁺]), adding base increases pH (decreases [H⁺]).

Application-Based Questions:

61. pH of Rainwater:

• pH 5.6 is slightly acidic due to natural CO₂ in the atmosphere forming carbonic acid.

62. pH Calculation:

• pH = -log[H⁺] = -log(1×10⁻⁵) = 5

63. HCl + NaOH Reaction:

• HCl + NaOH → NaCl + H₂O

64. Preparing pH 8 Solution:

• Use a weak base like NaHCO₃ or dilute NaOH until the pH meter or indicator shows pH 8.

65. Mixing HCl and NaOH:

• Equimolar amounts neutralize each other; the pH would be close to 7 if well-mixed.

66. Baking Soda with Vinegar:

• NaHCO₃ + HC₂H₃O₂ → NaC₂H₃O₂ + H₂O + CO₂

67. Acids on Metals Experiment:

• Place a piece of zinc in dilute HCl; observe hydrogen gas bubbles.

68. Phenolphthalein Color:

• Turns pink in a basic solution (pH > 8.2), indicating basicity.

69. Litmus Paper Use:

• Red litmus turns blue in base, blue turns red in acid.

70. Neutralization Experiment:

• Combine known volumes of acid (like HCl) and base (like NaOH) with an indicator; observe color change to neutral.

Critical Thinking Questions:

71. Ocean pH and Ecosystems:

• Acidification can dissolve coral reefs, affect shell formation in marine life, and alter food chains.

72. Household Cleaning Products:

• Strong acids/bases can be harmful, leading to need for careful handling, storage, and disposal, plus potential environmental impact.

73. Human Body pH:

• Enzymes function optimally within specific pH ranges; extreme pH can lead to health issues like acidosis or alkalosis.

74. Food pH and Preservation:

• Acidic pH inhibits bacterial growth, affecting food preservation, while basic pH can alter taste and texture.

75. Acid Mine Drainage:

• Ethical issues include environmental damage, health hazards, and the cost and responsibility of remediation efforts.

76. Soil pH and Crop Choice:

• Crops have optimal pH ranges; unsuitable pH can lead to nutrient lockout or toxicity, affecting yield and health.

77. Acids and Metal Containers:

• Acids can corrode metals, releasing harmful ions into the acid or causing container failure.

78. Neutralizing Acid Rain:

• Challenges include scale of application, cost, unintended environmental impacts, and source control of pollutants.

79. pH in Medical Diagnostics:

• Blood pH levels can indicate metabolic or respiratory conditions; urine pH can show kidney function.

80. Acid-Base Chemistry in Technology:

• Development of pH-sensitive materials, drug delivery systems, or environmental sensors based on acid-base reactions.