Introduction

Relevance of the Theme

Inorganic Functions are the foundation of Inorganic Chemistry, a branch of chemistry that studies substances that do not contain carbon in their composition. Among these functions, Salt stands out for its wide application in our daily lives. In fact, when we talk about salt, the first thing that comes to mind is culinary seasoning. But salt is much more than that, it is a fundamental component in many biological and industrial processes.

Understanding what salt is and its chemistry allows us to better understand chemical reactions, dissociation processes, ion formation, troposphere and ionosphere, as well as the function of sodium and chlorine in our bodies. Therefore, studying Salts establishes a bridge between Inorganic Chemistry and its real-life applications.

Contextualization

In the vast field of chemistry, Inorganic Functions are in the early stages of learning, specifically within General Chemistry units. It is at this moment that we begin to shape our understanding of the structure and reactivity of substances, which are the foundations for understanding more complex concepts.

Thus, the study of Salts, as a representative of the broader inorganic function, paves a valuable path by introducing the ionic nature of substances and the concepts of chemical reaction. Salts provide a concrete link between the theoretical world of chemistry and its many practical applications, from cooking to nanotechnology.

Within the curriculum of General Chemistry in the 1st year of High School, the study of Salts is generally accompanied by the introduction to the periodic table and the concept of ions. Therefore, a solid understanding of Salts is vital for progress not only within the topic of Inorganic Functions, but also for subsequent topics that are based on this basic understanding.

Theoretical Development

Components

• Salt, what is it?: Salt, in chemistry, is a substance formed by the reaction of an acid and a base, with the consequent release of one or more ions. The salt resulting from the reaction of an acid and a base is called a neutral salt. Salts are generally ionic compounds, which makes them soluble in water. The most common way to visualize this dissociation is that of table salt, which, in aqueous solution, dissociates into sodium ions (Na+) and chlorine ions (Cl-).

• Classification of Salts: Salts can be classified according to the origin of their acids and bases:

  • Binary Salts: Those formed by the reaction of a binary acid (HCl, HBr, HI, H2S, HCN) with a strong base (NaOH, KOH, Ca(OH)2, Mg(OH)2). Example: NaCl, table salt.

  • Ternary Salts: Result from the reaction of a ternary acid (H3BO3, H4SiO4, H2CO3, H2SO3, H3PO4) with a base. Example: Na2SO4, sodium sulfate.

  • Neutral, Acidic, and Basic Salts: Salts can also be classified according to their behavior in aqueous solution. Neutral salts do not change the pH of the solution, acidic salts release H+ (hydrogen ion) in the solution, decreasing the pH, and basic salts release OH- (hydroxide ion), increasing the pH.

• Properties of Salts:

  • Melting and Boiling Point: Salts, in general, have relatively high melting and boiling points due to the strength of the ionic bonds present between the ions.

  • Solubility: The solubility of salts is high in water, but may vary in other solvents, depending on the charge and size of the ions.

  • Conduction of Electricity: Salts, when dissolved in water or in a liquid state, conduct electricity. This occurs because the ions present in the solution are free to move and carry the electric current.

Key Terms

• Ionic Dissociation: Process by which an ionic compound separates into ions in the presence of a solvent, usually water.

• Ions: Electrically charged particles. Cations are positive ions, formed when an atom loses electrons. Anions are negative ions, formed when an atom gains electrons.

Examples and Cases

• Table Salt (NaCl): This is the classic example of salt. NaCl is a binary salt that, in aqueous solution, dissociates into sodium ions (Na+) and chlorine ions (Cl-). Although best known as a seasoning, NaCl has a crucial influence on many biological processes, including the functions of the nervous system and blood pressure regulation.

• Copper Sulfate (CuSO4): This is an example of a neutral salt. CuSO4 is a ternary salt resulting from the reaction of sulfuric acid (H2SO4) with a base. In aqueous solution, it dissociates into copper ions (Cu2+), sulfate ions (SO42-), and hydrogen ions (H+). CuSO4 is widely used in laboratories, especially in cation analysis.

• Calcium Carbonate (CaCO3): This is an example of a basic salt. In aqueous solution, CaCO3 dissociates into calcium ions (Ca2+) and carbonate ions (CO32-). Calcium carbonate is found in nature in the form of minerals such as calcite, aragonite, and marble.

In-depth study of these components, key terms, and examples will allow for a more comprehensive and applicable understanding of Salts in Inorganic Chemistry.

Detailed Summary

Key Points

• Composition and Formation: Salts are formed by the reaction of an acid and a base, resulting in the release of ions. Familiarity with the processes of ionization and dissociation is essential to understand the formation of salts.

• Classification: Salts can be classified as binary and ternary, depending on the characteristics of the acids that form them. Additionally, they can be classified as neutral, acidic, or basic, depending on their behavior in aqueous solution.

• Properties: The properties of salts, such as melting and boiling point, solubility, and conduction of electricity, are direct consequences of their ionic structure.

• Applications: Understanding salts is not limited to theoretical aspects but also finds practical applications in various aspects of our daily lives, industry, and science.

Conclusions

• Ionic Nature of Salts: Understanding salt as an ionic compound is essential to comprehend its formation and properties.

• Chemical Connections: The study of salts establishes a relationship between the fundamental concepts of Inorganic Chemistry, such as ionic dissociation, and the practical applications of these concepts.

• Importance of Salt: Salt plays a vital role in many biological and industrial processes, and its in-depth study opens doors to a greater understanding of these processes.

Suggested Exercises

1. Write the balanced chemical equation for the formation of table salt (NaCl) and identify the type of salt formed.

2. Classify the following salts: NaHCO3, K2SO4, and Ca(OH)2 according to the origin of their acids and bases.

3. Explain why table salt conducts electricity when dissolved in water, but not when in the solid state.