Q.:- You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic and basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
First of all, we put one strip of red litmus paper in each test tube. In one of the test tubes, the litmus paper will turn blue which indicates the solution in that test tube is basic. Out of the remaining two test tubes any one can be acid or neutral (distilled water). Now a drop of basic solution is mixed with a drop of each of the remaining two solutions separately. Then we check the nature of the drops of the mixture again with red litmus. There can be two results: