Question

You are provided with three test tube containing distilled water,an acid and a base solution respectively if u r given only blue litmus paper how do u identify the contents of each test tube

Answer 1

first take the blue litmus paper and dip it in the first testube if the litmus paper is still blue its distilled water l now dip the litmus paper in second test tube the litmus paper turns red so it is an acid  take the red litmus paper and dip it in the third testube  and it turns blue again so its a base
therefore
1st solution is neutral so its disttlled water
2nd solution is an acid 
3rd solution is base
HOPE THIS HELPS YOU

Answer 2

Blue litmus paper has non change on adding to base. Acid changes blue litmus paper to red . Distilled water will also not change the colour of litmus paper.