Chapter 22, Problem 42R

To determine

To Conclude: The given liquids are acid or base or neutral.

Explanation of Solution

Introduction:

Phenolphthalein is an indicator that is colorless in acids, but turns bright pink in bases.

There are three equal amounts of colorless liquids-A, B, and C.

When several drops of phenolphthalein is added to each liquid, A and B remain colourless, but C turns pink. This indicates liquid C is a basic solution; asphenolphthalein turns bright pink in bases.

When liquid C is added to A, the pink colour disappears. The disappearance of pinkcolour maybe due to neutralization of liquid C (a base) by liquid A. An acid only can neutralize a base.

Thus, liquid A can be assumed an acidic solution. When the rest of the liquid C is addedto B, the mixture becomes pink.The mixture maybe basic, as phenolphthaleingives pink color only in bases. As liquid C is already a base, liquid B has to be a neutral solution, for addition of a base (C) increases its pH and the mixture becomes basic.

Conclusion: From the changes in color of phenolphthalein, it can be concluded thatliquid A is an acidic solution, liquid B is a neutral solution and liquid C is a basic solution.