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Acids and Bases. — Science STD 8 — Question

Tamilnadu BoardEnglish MediumSTD 8ScienceAcids and Bases.4 Marks
Question
Write a note on:
  1. Litmus
  2. Phenolphthalein
  3. Methyl orange
✓

Answer

1. Litmus:
  • Litmus is the most common indicators used in the laboratories.
  • Litmus is a natural indicator which is extracted from lichens.
  • It is available in the form of solution or in the form of strips prepared by absorbing litmus solution on filter paper.
  • It is either red or blue in colour.
  • Blue litmus paper turns red in acidic solution and red litmus paper turns blue in the basic solution.
2. Phenolphthalein:
  • Phenolphthalein is a colourless compound.
  • Its alcoholic solution is used as an indicator.
  • It is colourless in acidic solution but turns pink in basic solution.
3. Methyl orange:
  • Solid methyl orange dissolved in hot water and its filtrate is used as an indicator.
  • It turns red in acidic solution and yellow in basic solution.

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