|
The end point titration of sodium hydroxide with hydrochloric acid usually is signaled by phenolphthalein indicator that undergoes a color change from pink in the base to colorless in the acid. Thus, the student is able to detect, visually, completion of the neutralization reaction.
The purpose of this experiment is to use unique acid-base indicator--the odor of raw onion--to indicate the end point of the titration of sodium hydroxide with hydrochloric acid. The use of this novel indicator allows the student to detect the completion of the neutralization reaction by olfaction rather than by sight.
The experiment is conducted so that the student can initially discover which solution, sodium hydroxide or hydrochloric acid, eliminates the raw onion odor. As a result, the solution that "captures" the olfactory indicator is identified. The titration of this solution is carried out in the presence of both the visual and olfactory indicators so that the student can compare the times at which these two very different indicators signal the end point of the neutralization reaction.
|
Citation
