Question 1 Page 18 - Chapter 2 Class 10 - Acids, Bases and Salts

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?

Answer:

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.