Question

Учащиеся Андрей, Саша и Инна проводили реакции ионного обмена. Инна взяла для опыта раствор гидроксида натрия и добавила к нему раствор хлороводородной кислоты. Андрей высказал мнение о том, что никакой реакции не получилось, так как никаких изменений учащиеся не наблюдали. Саша с ним не согласился и решил повторить опыт, но вначале добавить фенолфталеин. Почему он так решил поступить? Произошла ли реакция ионного обмена? Кто из учащихся прав? Изменится ли цвет индикатора? Опишите свои рассуждения.

Answer 1

Ответ:

Саша был прав. Реакция произошла

Объяснение:

Продуктом реакции стала поваренная соль (NaCL), а она растворима, тоесть осадка для окраски раствора не было. Цвет индикатора фенолфталеин изменится с красного на бесцветный, потому что сначала среда была щелочная(окраска красная), а когда добавили соляную кислоту среда стала нейтральной и раствор окраску потерял. Получается что Саша был прав

Answer 2

The Experiment and the Students' Observations

Andrey, Sasha, and Inna conducted an experiment on ion exchange reactions. Inna took a solution of sodium hydroxide and added hydrochloric acid to it. Andrey believed that no reaction occurred because they did not observe any changes. Sasha disagreed with Andrey and decided to repeat the experiment, but this time adding phenolphthalein at the beginning.

Sasha's Reasoning for Adding Phenolphthalein

Sasha decided to add phenolphthalein to the experiment because phenolphthalein is an indicator that can detect the presence of acids and bases. It changes color depending on the pH of the solution. By adding phenolphthalein, Sasha hoped to observe a color change that would indicate the occurrence of a reaction between the sodium hydroxide and hydrochloric acid.

Did an Ion Exchange Reaction Occur?

Based on Sasha's decision to add phenolphthalein, it can be inferred that Sasha believed an ion exchange reaction would occur between the sodium hydroxide and hydrochloric acid. Phenolphthalein is commonly used as an indicator in acid-base titrations, where it changes color at a specific pH range. If the reaction between sodium hydroxide and hydrochloric acid resulted in the formation of water and a salt, it would be considered an ion exchange reaction.

Who Was Correct?

To determine who was correct, we need to consider the observations made by Sasha after adding phenolphthalein. If Sasha observed a color change in the solution, it would indicate the presence of an acid-base reaction and confirm that an ion exchange reaction occurred. On the other hand, if no color change was observed, it would support Andrey's initial claim that no reaction occurred.

Possible Color Change of the Indicator

Phenolphthalein is colorless in acidic solutions and turns pink or magenta in basic solutions. In the experiment, if the hydrochloric acid reacted with the sodium hydroxide to form water and a salt, the resulting solution would be neutral. Therefore, the addition of phenolphthalein could potentially cause the solution to turn pink or magenta, indicating the presence of a base.

Conclusion

In conclusion, Sasha decided to add phenolphthalein to the experiment to detect the presence of an acid-base reaction. Based on Sasha's decision, it can be inferred that Sasha believed an ion exchange reaction would occur between the sodium hydroxide and hydrochloric acid. To determine who was correct, Sasha's observation of a color change after adding phenolphthalein is crucial. If a color change occurred, it would indicate the presence of an acid-base reaction and confirm that an ion exchange reaction took place.