(1) Some years ago, a crucial experimental error was made during the work-up of the reaction. Instead of adding the reaction mix
ture to the cold acid solution, the inverse addition was carried out. What do you think happened when the acid solution was added to the reaction mixture
Salts will be formed and the pH of the new mixture will fall.
Explanation:
What should be: The reaction mixture should be added to the cold acid solution.
The error: Cold acid solution was added to the reaction mixture.
What happens with this?
The neutralization of a solution creates salts. The combination of positive and negative ions in the reaction also forms water. Assuming the pH of the reaction mixture was neutral before the addition of the acid, after the addition of the acid solution the pH will drop. Recall that a neutral solution has a pH of 7. So the pH of this new solution will drop to less than 7 because of the addition of an acid.
If the required procedure for the chemical process was followed, the reaction mixture added to the cold acid would have resulted in a stronger base solution. In other words, the pH of the new solution would be higher.
Bond-breaking is an endothermic process. Energy is released when new bonds form. Bond-making is an exothermic process. Whether a reaction is endothermic or exothermic depends on the difference between the energy needed to break bonds and the energy released when new bonds form.
