Question

A few drops of phenolphthalein indicator were added to an unknown solution A. It acquired pink color. Now another unknown solution B was added to it dropwise and the solution ultimately became colorless. Predict the nature of solutions A and B.

Answer 1

1. The phenolphthalein indicator helps decide the nature of the solution by changing the color of the solution.
2. It turns colorless in acidic solutions and pink in basic solutions.

Case 1:

In this case, when the indicator was added to solution A, it acquired a pink color.

So, if the solution has acquired pink color it means solution A is basic in nature.

Case 2:

When solution B was added to solution A, it did not change the color.

This means that solution B neutralizes solution A as it is acidic.

Therefore, the nature of solution B is acidic.

In conclusion, the nature of solution A is basic and that of B is acidic.