Check sibling questions

You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?



We know that, 

  • In acidic medium, red litmus doesn't change colour
  • In basic medium, red litmus turns blue.
  • In neutral medium, red litmus doesn't change colour


  1. Start by dipping the red litmus paper into all three solutions. 
    • The solution which turns the red litmus paper into blue will be the basic solution .

  2. Since the red litmus paper has now turned blue , it can be used as a blue litmus paper.

  3. Dip the newly formed blue litmus paper into the remaining two solutions.

  4. We know blue litmus turns red in an acidic solution. 
    • The solution which turns the blue litmus paper into red is the acidic solution.

  5. The only remaining solution is the distilled water.


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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo