Question

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 1

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:

1. If the colour of red litmus turns blue, then the second solution is neutral (distilled water), and
2. If there is no change in colour and the litmus remains red, then the second solution is acidic. This is because acidic and basic solutions neutralize each other.
Thus, we can identify the contents of each test tube.

Simply
If the colour of red litmus does not change then it is acid. If the colour of red litmus changes to blue then it is base. If there is slight change in the colour of red litmus (such as purple) then it is distilled water.