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Quiz Chapter 6: Acid and Alkali

10 questions · Form 2 Science Bab 6: Acid and Alkali

Question 1 of 10Score: 0

What happens to the pH of an alkaline solution as an acid is gradually added to it during titration?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. What happens to the pH of an alkaline solution as an acid is gradually added to it during titration?

  1. The pH value increases toward 14
  2. The pH value decreases toward 7 and lower
  3. The pH remains constant at 14
  4. The pH drops instantly to 0
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Answer: B

Adding acid neutralises hydroxide ions in the alkali, causing the pH of the mixture to drop steadily toward pH 7.

2. What is the expected color change of Phenolphthalein indicator when added to a solution of Sodium Hydroxide (alkali)?

  1. Turns Red
  2. Turns Pink
  3. Turns Yellow
  4. Remains Colorless
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Answer: B

Phenolphthalein is colorless in acidic and neutral solutions, but turns pink in alkaline solutions.

3. Why is toothpaste formulated to be mildly alkaline?

  1. To increase the production of bacteria in the mouth
  2. To neutralise organic acids produced by oral bacteria from food debris
  3. To react with enamel to generate hydrogen gas
  4. To lower the pH of saliva below 4
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Answer: B

Oral bacteria break down food remnants into acids that decay tooth enamel; mildly alkaline toothpaste neutralises these acids.

4. What salt is formed when Hydrochloric Acid reacts with Calcium Hydroxide?

  1. Calcium Chloride
  2. Calcium Sulphate
  3. Sodium Chloride
  4. Calcium Carbonate
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Answer: A

Hydrochloric Acid + Calcium Hydroxide → Calcium Chloride + Water.

5. What color does Universal Indicator show in a neutral solution such as pure distilled water (pH 7)?

  1. Red
  2. Green
  3. Purple
  4. Yellow
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Answer: B

Universal Indicator turns green at pH 7, indicating a neutral medium.

6. Which action should be taken before discharging acidic effluent from factories into nearby rivers?

  1. Cooling the effluent without treatment
  2. Adding an alkali such as lime to neutralise the acid
  3. Adding more concentrated acid to dilute it
  4. Boiling the effluent to evaporate the acid
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Answer: B

Treating acidic industrial waste with an alkali neutralises the acid, preventing aquatic pollution and harm to river ecosystems.

7. What happens when a piece of dry blue litmus paper is placed into dry citric acid crystals?

  1. It turns red immediately
  2. It turns white due to bleaching
  3. No color change occurs
  4. It turns green
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Answer: C

Acids require water to ionize and produce hydrogen ions; without water, dry acid crystals cannot exhibit acidic properties to turn dry blue litmus paper red.

8. Which substance is commonly found in antacid tablets used to relieve stomach pain caused by gastritis?

  1. Sulfuric acid
  2. Magnesium hydroxide
  3. Sodium chloride
  4. Vinegar
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Answer: B

Antacids contain weak alkalis such as magnesium hydroxide or aluminium hydroxide to neutralise excess hydrochloric acid in the stomach.

9. In a laboratory experiment, a student finds a liquid with a pH value of 13. How should this liquid be classified?

  1. Strong acid
  2. Weak acid
  3. Neutral substance
  4. Strong alkali
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Answer: D

pH values between 11 and 14 indicate strong alkaline solutions.

10. Which ion is produced by all acids when dissolved in water?

  1. Hydroxide ion (OH-)
  2. Hydrogen ion (H+)
  3. Chloride ion (Cl-)
  4. Sodium ion (Na+)
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Answer: B

Acids are substances that ionize in water to form hydrogen ions (H+), which are responsible for their acidic properties.

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