Chapter 7. Classification of Chemical Reactions by Electronic Processes
11 topics with brief reviews: definitions, key facts, and class questions.
In this chapter, we examine chemical reactions through the lens of electron and proton transfer. This is an absolute foundation for understanding processes in the living organism: from the mechanisms of maintaining blood acid-base balance to tissue respiration.
The section covers two fundamental groups of interactions. The first involves processes without changes in oxidation states: modern acid-base theories, neutralization and ion-exchange reactions, salt hydrolysis, and the specifics of amphoteric compounds. The second group is dedicated to oxidation-reduction (redox) reactions. Here, we analyze in detail the effect of the environment (pH) on redox processes, learn how to balance them, calculate the redox potential, and understand the essence of electrolysis.
In practical classes and colloquia, you will primarily be required to have an impeccable skill in balancing complex redox reactions (especially using the ion-electron method taking the medium into account). Students also traditionally make many errors in predicting salt hydrolysis products and calculating redox potentials—pay special attention to these topics.
Do different acid-base theories contradict each other?
No, they do not contradict each other at all. Different theories simply describe the behavior of acids and bases (antagonist particles) under various conditions and from different perspectives.
Why is the neutralization of a strong acid with a strong base irreversible?
During the reaction, water is formed—a very weak electrolyte. Since the starting substances are completely dissociated, the reverse proton transfer from a water molecule to a strong acid anion is practically impossible.
Because the potential ion exchange yields compounds that are highly soluble in water. Since neither a weak electrolyte nor a precipitate is formed, the reaction does not proceed.
Because the potential ion exchange yields compounds that are highly soluble in water. Since neither a weak electrolyte nor a precipitate is formed, the reaction does not proceed.
What is the degree of hydrolysis?
This is a value showing the fraction of a substance that has reacted with water. It is equal to the ratio of the concentration of the hydrolyzed portion to the initial salt concentration.
Why does zinc hydroxide dissolve in excess alkali?
In an alkaline medium, zinc hydroxide exhibits acidic properties. It adds extra hydroxide ions, resulting in the formation of a complex water-soluble salt—sodium tetrahydroxozincate.
How do redox reactions differ from acid-base reactions?
In redox reactions, the oxidation state of atoms always changes due to electron transfer. In acid-base reactions, when an electron pair is transferred from a donor to an acceptor, the oxidation states remain unchanged.
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