Indicators in Chemistry
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Indicators in Chemistry

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Questions and Answers

What color change occurs when a base is added to phenolphthalein?

  • It remains white
  • It turns pink (correct)
  • It turns yellow
  • It turns blue
  • Which natural indicator turns reddish when mixed with an acid?

  • Turmeric
  • Onion
  • Red cabbage juice (correct)
  • Litmus
  • Which of the following indicators does NOT change its color with acid?

  • Methyl orange
  • Phenolphthalein
  • Turmeric (correct)
  • Litmus
  • What happens to the smell of vanilla when mixed with a base?

    <p>It vanishes</p> Signup and view all the answers

    What is a characteristic property of acids in aqueous solutions?

    <p>They release H+ ions</p> Signup and view all the answers

    Which acid is classified as a natural acid and is commonly found in vinegar?

    <p>Acetic acid</p> Signup and view all the answers

    What gas is produced when hydrochloric acid reacts with zinc metal?

    <p>Hydrogen</p> Signup and view all the answers

    Which of the following acids does NOT produce carbon dioxide when reacted with a metal carbonate?

    <p>Phosphoric acid</p> Signup and view all the answers

    Which of the following compounds represents a natural acid derived from citrus fruits?

    <p>Citric acid</p> Signup and view all the answers

    When an acid reacts with a metal carbonate, which of the following is NOT a product of the reaction?

    <p>Hydrogen gas</p> Signup and view all the answers

    Study Notes

    Indicators

    • Substances that indicate acidity or basicity of a solution through color change.

    Types of Indicators

    Natural Indicators

    • Derived from natural sources.
    • Common examples include:
      • Litmus: Obtained from lichens; purple in solution.
        • Blue litmus turns red in acid; red turns blue in base.
      • Turmeric: Yellow in color.
        • Turns reddish-brown with a base; no color change with acid.
      • Red Cabbage: Purple juice.
        • Changes to reddish with acid; greenish with base.

    Olfactory Indicators

    • Change smell when mixed with acids or bases.
    • Notable examples:
      • Onion: Loses odor when added to base; retains smell with acid.
      • Vanilla: Smell disappears with base; unaffected by acid.

    Synthetic Indicators

    • Created in the laboratory.
    • Examples include:
      • Phenolphthalein: Colorless in acid; turns pink in base.
      • Methyl Orange: Orange initially; appears red in acid and yellow in base.

    Acids

    • Characterized by sour taste and the ability to turn blue litmus red; they dissociate to release H+ ions in water.
    • Common examples:
      • Sulphuric acid (H2SO4)
      • Acetic acid (CH3COOH)
      • Nitric acid (HNO3)

    Properties of Acids

    • Sour taste.
    • Blue litmus turns red.
    • Conduct electricity in solution.
    • Release H+ ions when dissolved in water.

    Types of Acids

    • Natural (Organic) Acids: Obtained from natural sources.
      • Examples:
        • Methanoic acid (HCOOH)
        • Acetic acid (Vinegar)
        • Citric acid (Citrus fruits)
    • Mineral Acids: Prepared from minerals; also known as inorganic or synthetic acids.
      • Examples:
        • Hydrochloric acid (HCl)
        • Sulphuric acid (H2SO4)
        • Nitric acid (HNO3)

    Chemical Properties of Acids

    • Reaction with Metals: Produces hydrogen gas and respective salt.

      • For example, reaction of hydrochloric acid with zinc yields zinc chloride and hydrogen gas.
    • Reaction with Metal Carbonates: Yields carbon dioxide gas, water, and respective salts.

      • Example with hydrochloric acid and sodium carbonate results in sodium chloride, carbon dioxide, and water.

    Testing for Hydrogen Gas

    • Presence of hydrogen gas confirmed by bringing a lighted candle near the test; it burns with a pop sound, indicating hydrogen evolution.

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    Description

    This quiz explores the concept of indicators in chemistry, focusing on their role in determining the acidic or basic nature of solutions. Learn about the types of indicators, including natural indicators like litmus and turmeric, and their applications in identifying pH levels.

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