Which of the following is a characteristic property of acids? 

The correct answer is They turn blue litmus paper red.

Key Points

• Acids turn blue litmus paper red, which is a common test to identify acidic substances.
• Acids have a sour taste, a characteristic resulting from the presence of hydrogen ions (H⁺).
• Acids have a pH less than 7, indicating their acidic nature on the pH scale.
• Acids react with bases in a neutralization reaction to form salt and water.
• Common examples of acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and citric acid.

Additional Information

• Litmus Paper:
  • It is a dye-imbued paper used to test the acidity or basicity of a substance.
  • Blue litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic conditions.
• pH Scale:
  • The pH scale ranges from 0 to 14, with 7 being neutral.
  • Values less than 7 indicate acidity, and values greater than 7 indicate basicity.
• Neutralization Reaction:
  • A chemical reaction in which an acid and a base react to form water and a salt.
  • This reaction typically results in the pH of the resulting solution being closer to neutral (pH 7).
• Common Acids in Daily Life:
  • Hydrochloric Acid (HCl): Found in stomach acid, aiding digestion.
  • Citric Acid: Present in citrus fruits like lemons and oranges.
  • Acetic Acid: The main component of vinegar.
• Uses of Acids:
  • In the food industry for flavoring and preservation.
  • In the chemical industry for manufacturing fertilizers, dyes, and explosives.
  • In medicine for various treatments and as disinfectants.