Introduction to Bases: Gates to the Realm of Inorganic Compounds

Relevance of the Theme

Bases, one of the most powerful and ubiquitously present inorganic functions in Chemistry, play crucial roles in numerous chemical reactions and biological processes. They are essential for understanding the acid-base theory, one of the pillars of Chemistry.

Bases, alongside acids, are fundamental components in the study of chemical solutions, providing the ability to regulate pH and, therefore, the acid-base balance. Their applications range from household cleaning solutions to the neutralization of stomach acids in medications.

Contextualization

In the vast structure of the Chemistry curriculum, bases are one of the 'Gates to the Realm of Inorganic Compounds.' It is here that we begin to understand that acids and bases are counterparts, presenting opposite properties. While acids donate protons, bases receive them.

The inorganic function of a substance is defined by its chemical and physical properties. The study of each of them presents us with a new range of possibilities and applications.

In the 1st year of High School, the study of bases marks the transition to a deeper level of understanding of Chemistry. They are the starting point for understanding more complex concepts, such as redox reactions, solubility, and chemical equilibria.

Theoretical Development

Components

• Classical Definition of Arrhenius Bases: According to Svante Arrhenius, bases are substances that, in aqueous solution, release hydroxide ions OH-. This model, although simple, allows us to understand the properties and behavior of bases in nature.

• Extended Definition of Bronsted-Lowry Bases: In contrast to the Arrhenius model, which restricts the definition of bases to aqueous solutions, the physical chemist Bronsted-Lowry introduces the concept of proton transfer. In this model, bases are proton donors (H+). In other words, a base is any species that can accept a proton and form a conjugate acid species.

• Lewis Bases Definition: According to chemist G.N. Lewis, any substance that has a pair of electrons available for donation is a base. This model, the broadest of the three, expands the concepts of acidity and basicity beyond proton transfer.

Key Terms

• Strength of Bases: Determined by the ability to donate OH- or accept protons (H+). Strong bases completely dissociate in aqueous solutions, releasing all or almost all OH- or accepting H+.

• Weak Bases: Bases that undergo partial dissociation in solution.

• Hydroxides: They are the most common binary inorganic compounds (formed by two elements) that act as bases. They are formed by the combination of a metallic cation and a hydroxide anion (OH-).

Examples and Cases

• NaOH (Sodium Hydroxide): This compound, used in soap manufacturing, is one of the most well-known hydroxides. It is a strong base that ionizes completely in solution, releasing OH-.

• Ba(OH)2 (Barium Hydroxide): It is a common hydroxide used in the chemical industry and paint production. It is a strong base that releases two OH- ions per formula, for each molecule of Ba(OH)2 that dissociates.

• NH3 (Ammonia): Ammonia is an example of a base according to Lewis's definition. Although it does not release OH- in solution, it accepts protons to form the ammonium ion (NH4+), which is an acidic species.

Detailed Summary

Key Points

• Acid-Base Duality: Bases, along with acids, represent the heart of the acid-base theory, providing the necessary counterpart for proton donation.

• Base Definitions: Three base definition models were presented, each with a different and complementary view. The Bronsted-Lowry model allows for a better understanding of the reaction between acids and bases, while the Lewis model expands the concept of basicity.

• Strength of Bases: The strength of a base is related to its ability to donate hydroxides or accept protons. Strong bases completely release OH- or accept protons, while weak bases perform these processes partially.

• Hydroxides: These compounds, formed by the combination of a metal and the hydroxide, are the most common inorganic bases. Their dissociation in solution releases OH-, characterizing them as bases.

Conclusions

• Bases, alongside acids, are fundamental components in the study of chemical solutions, providing the ability to regulate pH and, therefore, the acid-base balance.

• Base definitions are not limited to a specific function but vary according to the model, highlighting the complex nature of bases.

• Classifying a base as strong or weak is related to its ability to donate hydroxides (OH-) or accept protons (H+).

Exercises

1. Define in your own understanding what bases are, using the definitions of Arrhenius, Bronsted-Lowry, and Lewis. Compare and contrast these definitions and explain the importance of each of them.

2. For each of the following compounds, identify if it can be classified as an Arrhenius base, a Bronsted-Lowry base, or both: NaOH, Ba(OH)2, NH3. Explain your answer.

3. Classify the following bases as strong or weak, and explain the reasoning behind your classification: KOH, NH4OH, Mg(OH)2.