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Quiz Chapter 6: Acid and Alkali

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

10 questions · plays in fullscreen

Full Question List & Answer Key

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

1. 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.

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. 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.

4. 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.

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 indicator turns RED in an acidic solution and YELLOW in an alkaline solution?

  1. Phenolphthalein
  2. Methyl Orange
  3. Litmus Paper
  4. Filter Paper
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Answer: B

Methyl Orange turns red in acidic conditions and yellow in neutral or alkaline conditions.

7. 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.

8. Why do farmers add slaked lime (calcium hydroxide) to agricultural soil?

  1. To increase soil acidity for better seed germination
  2. To neutralise overly acidic soil and improve crop growth
  3. To kill earthworms and insects
  4. To increase soil moisture retention
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Answer: B

Slaked lime is an alkaline substance added to acidic soil to neutralise excess acidity and achieve an optimal pH for crops.

9. Which pH value indicates a strong acid solution?

  1. pH 1
  2. pH 5
  3. pH 7
  4. pH 13
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Answer: A

The pH scale ranges from 0 to 14. A pH value closest to 0 (such as pH 1) represents a strong acid.

10. 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.

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