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Acids, Bases and Salts — Science STD 7 — Question

Gujarat BoardEnglish MediumSTD 7ScienceAcids, Bases and Salts1 Mark
MCQ
Aqueous solution of a base:
  • A
    Turns blue litmus into red
  • ✓
    Turns red litmus into blue
  • C
    Turns litmus solution colourless
  • D
    Has no effect on litmus solutio
✓

Answer

Correct option: B.
Turns red litmus into blue
Red litmus contains a weak diprotic acid. When it is exposed to a basic compound, the hydrogen ions react with the added base. The conjugate base formed from the litmus acid has a blue color, so the wet red litmus paper turns blue in an alkaline solution.
Bases turn the color of red litmus paper to blue.

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