Chapter 22, Problem 38R

To determine

To Summarize: The process for titration of an unknown basic solution with an acidic solution of known concentration.

Explanation of Solution

Introduction:

The process of complete reaction ofa solution of known concentration with a solution of unknown concentration is known as titration.

In this titration, the acidic solution of known concentration is the standard solution, and the basic solution’s concentration is unknown.

A few drops of an indicator, such as phenolphthalein, is added to a measured volume of the basic solution. Phenolphthalein is pink in color in a base, but turns colourless in acid.The acidic solution is then slowly addedto the indicator-base mixture.

Towards the end of the titration, the acid is added drop by drop tillthe last drop of the acid turns the solution colorless and it remains so. The point at which the change in color persists is known as the endpoint. At this point, the base is completely neutralized by the acid.

The known volume and concentration of acid and the known volume of the base is used to calculate the concentration of the basic solution.

Conclusion:

In the process of titration, the acidic solution is initially added slowly to the indicator-base solution and then it is added drop by drop until a color change occurs. The point at which the change in color persists is the point at which thebase is completely neutralized by the acid.