Question 1 — A solution turns the red litmus - Questions at the end of the chapter - Chapter 2 Class 7 - Exploring Substances: Acidic, Basic, and Neutral

Last updated at August 16, 2026 by

Q1 (Medium): A solution turns the red litmus paper to blue. Excess addition of which of the following solution would reverse the change? (i) Lime water (ii) Baking soda (iii) Vinegar (iv) Common salt solution

Answer:
We have studied that basic substances turn red litmus blue and acidic substances turn blue litmus red . This is why we need an acidic solution to reverse the change.

  • Solution is basic - turns red litmus blue
  • Need acidic substance to reverse the change
  • Vinegar is acidic - will turn blue back to red
  • Other options are basic or neutral substances
Reversing Litmus Colour Change Step 1 Basic solution turns red litmus blue Step 2 Add acidic substance (vinegar) Step 3 Blue litmus turns back to red Answer: (iii) Vinegar
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