Class X Science. Lesson 2: Acids, Bases and Salts. 100 Important Questions and Answers.

Class X Science (SEBA Assam)

Lesson 2: Acids, Bases and Salts

100 Important Questions, Answers & Short Explanations


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1. What are acids?

Answer:
Acids are substances that release H⁺ ions in water.

Explanation:
They taste sour and turn blue litmus red.


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2. What are bases?

Answer:
Bases are substances that release OH⁻ ions in water.

Explanation:
They are bitter and feel soapy.


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3. What is an indicator?

Answer:
A substance that shows whether a solution is acidic or basic.

Explanation:
Indicators change color in acids and bases.


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4. Name one natural indicator.

Answer:
Litmus.

Explanation:
It is obtained from lichens.


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5. Which color does acid turn blue litmus?

Answer:
Red.


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6. Which color does base turn red litmus?

Answer:
Blue.


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7. Name a mineral acid.

Answer:
Hydrochloric acid.


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8. Name an organic acid.

Answer:
Acetic acid.


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9. What is the chemical formula of hydrochloric acid?

Answer:
HCl.


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10. What is the formula of acetic acid?

Answer:
CH₃COOH.


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11. Why do acids conduct electricity?

Answer:
Because they produce ions in solution.


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12. Why do dry acids not show acidic behavior?

Answer:
Because water is absent.


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13. Which gas evolves when zinc reacts with acid?

Answer:
Hydrogen gas.


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14. Write the reaction between zinc and hydrochloric acid.

Answer:
Zn + 2HCl → ZnCl₂ + H₂


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15. Which gas is produced when acids react with carbonates?

Answer:
Carbon dioxide.


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16. What happens when CO₂ passes through lime water?

Answer:
Lime water becomes milky.


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17. Why does lime water turn milky?

Answer:
Due to formation of calcium carbonate.


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18. What is the formula of lime water?

Answer:
Ca(OH)₂.


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19. Which acid is found in lemon?

Answer:
Citric acid.


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20. Which acid is found in curd?

Answer:
Lactic acid.


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21. Which acid is present in tamarind?

Answer:
Tartaric acid.


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22. Which acid is found in ant sting?

Answer:
Formic acid.


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23. Why is antacid used?

Answer:
To reduce stomach acidity.


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24. Name one antacid.

Answer:
Magnesium hydroxide.


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25. What is neutralization?

Answer:
Reaction between acid and base forming salt and water.


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26. Write one neutralization reaction.

Answer:
HCl + NaOH → NaCl + H₂O


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27. What is pH?

Answer:
It indicates acidity or basicity of a solution.


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28. What is the pH of pure water?

Answer:
7.


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29. Which pH value shows acidity?

Answer:
Less than 7.


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30. Which pH value shows basicity?

Answer:
More than 7.


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31. What does low pH indicate?

Answer:
Strong acidity.


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32. What does high pH indicate?

Answer:
Strong basicity.


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33. What is universal indicator?

Answer:
A mixture of several indicators.


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34. What is tooth decay caused by?

Answer:
Acids in the mouth.


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35. Why should toothpaste be basic?

Answer:
To neutralize mouth acids.


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36. Which acid is present in stomach?

Answer:
Hydrochloric acid.


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37. What happens if stomach acid increases?

Answer:
Indigestion and irritation occur.


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38. What is common salt?

Answer:
Sodium chloride.


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39. Write the formula of common salt.

Answer:
NaCl.


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40. What is brine?

Answer:
Concentrated sodium chloride solution.


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41. What is chlor-alkali process?

Answer:
Electrolysis of brine.


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42. Name products of chlor-alkali process.

Answer:
Sodium hydroxide, chlorine and hydrogen.


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43. Write chlor-alkali reaction.

Answer:
2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂


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44. Which gas forms at anode?

Answer:
Chlorine gas.


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45. Which gas forms at cathode?

Answer:
Hydrogen gas.


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46. What is bleaching powder?

Answer:
Calcium oxychloride.


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47. Write formula of bleaching powder.

Answer:
CaOCl₂.


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48. How is bleaching powder prepared?

Answer:
By passing chlorine through slaked lime.


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49. Give one use of bleaching powder.

Answer:
Disinfecting water.


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50. What is baking soda?

Answer:
Sodium hydrogen carbonate.


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51. Write formula of baking soda.

Answer:
NaHCO₃.


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52. Why is baking soda used in baking?

Answer:
It releases carbon dioxide.


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53. What is baking powder?

Answer:
Mixture of baking soda and tartaric acid.


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54. Why is tartaric acid added to baking powder?

Answer:
To remove bitter taste.


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55. What is washing soda?

Answer:
Sodium carbonate decahydrate.


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56. Write formula of washing soda.

Answer:
Na₂CO₃·10H₂O.


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57. Give one use of washing soda.

Answer:
Softening hard water.


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58. What is water of crystallization?

Answer:
Fixed water molecules present in crystals.


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59. Which salt contains water of crystallization?

Answer:
Washing soda.


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60. What is Plaster of Paris?

Answer:
Calcium sulphate hemihydrate.


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61. Write formula of Plaster of Paris.

Answer:
CaSO₄·½H₂O.


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62. How is Plaster of Paris prepared?

Answer:
By heating gypsum.


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63. What is gypsum?

Answer:
Calcium sulphate dihydrate.


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64. Write formula of gypsum.

Answer:
CaSO₄·2H₂O.


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65. Why is POP stored carefully?

Answer:
It absorbs moisture and hardens.


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66. Give one use of POP.

Answer:
Making statues.


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67. Which ion causes acidity?

Answer:
H⁺ ion.


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68. Which ion causes basic nature?

Answer:
OH⁻ ion.


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69. What is an olfactory indicator?

Answer:
Indicator identified by smell.


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70. Give one example of olfactory indicator.

Answer:
Onion.


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71. What happens to turmeric in base?

Answer:
It becomes reddish-brown.


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72. What happens to turmeric in acid?

Answer:
No color change occurs.


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73. What is the nature of metal oxides?

Answer:
Basic.


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74. What is the nature of non-metal oxides?

Answer:
Acidic.


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75. Give one example of basic oxide.

Answer:
Calcium oxide.


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76. Give one example of acidic oxide.

Answer:
Sulphur dioxide.


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77. What is the pH range?

Answer:
0 to 14.


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78. Which pH shows strongest acid?

Answer:
0 or 1.


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79. Which pH shows strongest base?

Answer:
14.


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80. Why should acids be diluted carefully?

Answer:
Because heat is produced.


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81. Which should be added first during dilution?

Answer:
Acid into water.


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82. Why is water not added directly to acid?

Answer:
It may splash violently.


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83. What is sodium hydroxide commonly called?

Answer:
Caustic soda.


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84. What is potassium hydroxide commonly called?

Answer:
Caustic potash.


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85. What is slaked lime?

Answer:
Calcium hydroxide.


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86. Write formula of slaked lime.

Answer:
Ca(OH)₂.


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87. What is quick lime?

Answer:
Calcium oxide.


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88. Write formula of quick lime.

Answer:
CaO.


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89. Why does bee sting pain occur?

Answer:
Because acid enters the skin.


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90. How can bee sting pain be reduced?

Answer:
Using baking soda paste.


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91. What is acid rain?

Answer:
Rainwater containing acidic pollutants.


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92. Which gases cause acid rain?

Answer:
Sulphur dioxide and nitrogen oxides.


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93. What is the nature of soap solution?

Answer:
Basic.


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94. Why does rainwater conduct electricity?

Answer:
Due to dissolved salts and gases.


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95. What happens when acid reacts with base?

Answer:
Salt and water form.


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96. What happens when acid reacts with metal carbonate?

Answer:
Salt, water and carbon dioxide form.


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97. Which gas gives pop sound on burning?

Answer:
Hydrogen.


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98. Why is chlorine used for water purification?

Answer:
It kills harmful microorganisms.


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99. What happens when POP mixes with water?

Answer:
It changes into gypsum.


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100. Why is washing soda called hydrated crystal?

Answer:
Because it contains water molecules in crystal form.