Question

You are provided with there test tubes A, B and C which contain distilled water, acidic solution and basic solution respectively. If you are given blue litmus paper only, how will you identify the contents of each test tube?

CBSE Class X Science SA 2 (3 Marks)

Answer 1

Put blue litmus paper in all the three test tubes. In one test tube it will turn red that is acid. Now put red litmus paper in both the test tubes in one it will turn to blue that is base and the third one is distilled water. 

Answer 2

If you are given blue litmus paper only and are supposed to identify the contents of each test tube A, B and C which contain distilled water, acidic solution and the basic solution we will do the following:

• We will add blue litmus to all three test tubes
• the one with the acid will turn red

Here, we identify that Test tube B contains an Acidic solution

• now we will add another litmus into red solution
• we will take both the litmus papers from test tube B that would have turned red due to reaction, blue litmus turns Red in Acids.

• now place the red litmus into Test tubes A and B
• the one with water will not change the colour of the litmus
• the test tube that turns red litmus blue is the Basic solution.

Therefore, we can identify the contents of each test tube.