1. What color does blue litmus paper turn when dipped in an acidic solution?
A. Green
B. Red
C. Yellow
D. Colorless
Show Answer
Answer: B. Red
Explanation: Acids turn blue litmus paper red.
2. Which gas is evolved when an acid reacts with a metal?
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide
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Answer: C. Hydrogen
Explanation: Acid + Metal → Salt + Hydrogen gas.
3. What is the pH value of a neutral aqueous solution at 25°C?
Show Answer
Answer: B. 7
Explanation: A neutral solution like pure water has a pH equal to 7.
4. Sodium hydroxide (NaOH) is a strong base. What color will it turn phenolphthalein indicator?
A. Pink
B. Yellow
C. Red
D. Colorless
Show Answer
Answer: A. Pink
Explanation: Phenolphthalein gives a pink color in basic solutions and remains colorless in acidic solutions.
5. Which acid is present in sour milk or curd?
A. Citric acid
B. Acetic acid
C. Lactic acid
D. Tartaric acid
Show Answer
Answer: C. Lactic acid
Explanation: Curd and sour milk contain lactic acid.
6. What is the chemical name of Baking Soda?
A. Sodium carbonate
B. Sodium hydrogen carbonate
C. Calcium hydroxide
D. Sodium chloride
Show Answer
Answer: B. Sodium hydrogen carbonate
Explanation: Baking soda is Sodium Hydrogen Carbonate (NaHCO₃) or Sodium Bicarbonate.
7. The chemical formula of Plaster of Paris is:
A. CaSO₄ · 2H₂O
B. CaSO₄ · ½H₂O
C. CuSO₄ · 5H₂O
D. Na₂CO₃ · 10H₂O
Show Answer
Answer: B. CaSO₄ · ½H₂O
Explanation: Plaster of Paris is Calcium Sulfate Hemihydrate (CaSO₄ · ½H₂O).
8. What happens when carbon dioxide gas is passed through lime water for a short time?
A. Turns blue
B. Turns milky
C. Becomes brown
D. Remains colorless
Show Answer
Answer: B. Turns milky
Explanation: Insoluble calcium carbonate (CaCO₃) forms, making the lime water turn milky.
9. Tooth decay starts when the pH of the mouth drops below:
A. 5.5
B. 6.5
C. 7.5
D. 8.5
Show Answer
Answer: A. 5.5
Explanation: Tooth enamel (calcium hydroxyapatite) begins to corrode when mouth pH falls below 5.5.
10. Water soluble bases are specifically known as:
A. Acids
B. Salts
C. Alkalis
D. Indicators
Show Answer
Answer: C. Alkalis
Explanation: Bases that dissolve in water are called alkalis (e.g., NaOH, KOH).
11. What acid is injected into skin during an ant sting that causes severe pain?
A. Acetic acid
B. Methanoic acid
C. Oxalic acid
D. Tartaric acid
Show Answer
Answer: B. Methanoic acid
Explanation: Ant sting contains methanoic acid (formic acid).
12. Which of the following salts does NOT contain water of crystallization?
A. Blue vitriol
B. Baking soda
C. Washing soda
D. Gypsum
Show Answer
Answer: B. Baking soda
Explanation: NaHCO₃ does not contain water molecules of crystallization, whereas gypsum, blue vitriol, and washing soda do.
13. The reaction between an acid and a base to form salt and water is called a:
A. Combination reaction
B. Neutralization reaction
C. Decomposition reaction
D. Displacement reaction
Show Answer
Answer: B. Neutralization reaction
Explanation: Acid + Base → Salt + Water is a neutralization reaction.
14. What is the pH range of the human body for proper physiological survival?
A. 2.0 - 3.0
B. 5.5 - 6.5
C. 7.0 - 7.8
D. 9.0 - 10.5
Show Answer
Answer: C. 7.0 - 7.8
Explanation: Our body functions efficiently within a narrow pH range of 7.0 to 7.8.
15. Chemical formula of Bleaching Powder is:
A. CaOCl₂
B. Ca(OH)₂
C. CaCl₂
D. CaCO₃
Show Answer
Answer: A. CaOCl₂
Explanation: Bleaching powder is Calcium Oxychloride (CaOCl₂).
16. Which substance is used by doctors for supporting fractured bones in the right position?
A. Gypsum
B. Plaster of Paris
C. Washing soda
D. Bleaching powder
Show Answer
Answer: B. Plaster of Paris
Explanation: Plaster of Paris sets into a hard solid mass when mixed with water and supports broken bones.
17. Acid rain occurs when the pH of rainwater drops below:
A. 7.0
B. 6.5
C. 5.6
D. 4.0
Show Answer
Answer: C. 5.6
Explanation: Rainwater is called acid rain when its pH value is less than 5.6.
18. What is the primary acid present in vinegar?
A. Oxalic acid
B. Acetic acid
C. Citric acid
D. Hydrochloric acid
Show Answer
Answer: B. Acetic acid
Explanation: Vinegar contains 5-8% acetic acid (ethanoic acid) in water.
19. Which gas is liberated during the Chlor-Alkali process along with NaOH at the cathode?
A. Chlorine gas
B. Hydrogen gas
C. Oxygen gas
D. Nitrogen gas
Show Answer
Answer: B. Hydrogen gas
Explanation: In the Chlor-alkali process, H₂ gas is liberated at the cathode and Cl₂ gas at the anode.
20. What is the nature of Non-Metallic Oxides?
A. Basic
B. Acidic
C. Neutral
D. Amphoteric
Show Answer
Answer: B. Acidic
Explanation: Non-metallic oxides (like CO₂, SO₂) react with bases to form salt and water, showing acidic nature.
21. What is the nature of Metallic Oxides?
A. Acidic
B. Basic
C. Neutral
D. Highly acidic
Show Answer
Answer: B. Basic
Explanation: Metallic oxides (like MgO, CaO) react with acids to give salt and water, making them basic oxides.
22. An aqueous solution turns red litmus paper blue. Its pH is likely to be:
Show Answer
Answer: D. 10
Explanation: Turning red litmus blue indicates a basic solution, which has a pH greater than 7 (pH = 10).
23. Which of the following indicators is an olfactory indicator?
A. Litmus
B. Clove oil
C. Methyl orange
D. Turmeric
Show Answer
Answer: B. Clove oil
Explanation: Clove oil, onion, and vanilla change smell in acidic or basic media (olfactory indicators).
24. What is the formula of Washing Soda?
A. Na₂CO₃ · 10H₂O
B. NaHCO₃
C. Na₂CO₃ · H₂O
D. NaOH
Show Answer
Answer: A. Na₂CO₃ · 10H₂O
Explanation: Washing soda is Hydrated Sodium Carbonate (Na₂CO₃ · 10H₂O).
25. Which acid is present in tomatoes?
A. Citric acid
B. Oxalic acid
C. Tartaric acid
D. Acetic acid
Show Answer
Answer: B. Oxalic acid
Explanation: Tomatoes naturally contain oxalic acid.
26. Which ion is responsible for the acidic property of an aqueous solution?
A. OH⁻
B. H⁺ / H₃O⁺
C. Cl⁻
D. Na⁺
Show Answer
Answer: B. H⁺ / H₃O⁺
Explanation: Hydrogen ions (H⁺) or hydronium ions (H₃O⁺) give acidic character to solutions.
27. Which ion is responsible for the basic property of a solution in water?
A. H⁺
B. OH⁻
C. SO₄²⁻
D. CO₃²⁻
Show Answer
Answer: B. OH⁻
Explanation: Hydroxide ions (OH⁻) are released by bases in water and confer basic properties.
28. What is the chemical formula of Gypsum?
A. CaSO₄ · ½H₂O
B. CaSO₄ · 2H₂O
C. CuSO₄ · 5H₂O
D. FeSO₄ · 7H₂O
Show Answer
Answer: B. CaSO₄ · 2H₂O
Explanation: Gypsum is Calcium Sulfate Dihydrate (CaSO₄ · 2H₂O).
29. Concentrated acid should always be diluted by adding:
A. Water to acid slowly
B. Acid to water slowly with constant stirring
C. Water to acid all at once
D. Mixing both rapidly
Show Answer
Answer: B. Acid to water slowly with constant stirring
Explanation: Dilution is highly exothermic. Adding water to acid can cause splashing and explosive heat generation.
30. What salt is formed when zinc metal reacts with sodium hydroxide solution?
A. Sodium zincate
B. Zinc oxide
C. Sodium oxide
D. Zinc hydroxide
Show Answer
Answer: A. Sodium zincate
Explanation: Zn + 2NaOH → Na₂ZnO₂ (Sodium zincate) + H₂↑.
