Learning Outcomes
i. Define Arrhenius acids and bases according to their behavior in aqueous solutions.
ii. Understand the characteristics and properties of Arrhenius acids and bases.
iii. Explain the dissociation of Arrhenius acids and bases in water to produce hydrogen or hydroxide ions.
iv. Recognize common examples of Arrhenius acids and bases in everyday life.
Introduction
In the realm of chemistry, acids and bases are fundamental concepts that play a crucial role in various chemical reactions and processes. In this lesson, we embark on a journey to explore Arrhenius acids and bases, the first of many acid-base theories. Through this exploration, we will delve into the characteristics, behaviors, and dissociation of these substances, laying a solid foundation for further understanding of acid-base chemistry.
i. Defining Arrhenius Acids and Bases
Svante Arrhenius, a Swedish chemist, proposed the first comprehensive theory of acids and bases in 1884. According to Arrhenius, an acid is a substance that increases the concentration of hydrogen ions (H+) in aqueous solution, while a base is a substance that increases the concentration of hydroxide ions (OH-) in aqueous solution.
Characteristics of Arrhenius Acids
Arrhenius acids typically exhibit the following characteristics:
- Sour taste
- Ability to conduct electricity in aqueous solutions
- Ability to react with metals to produce hydrogen gas
- Ability to turn litmus paper red
Characteristics of Arrhenius Bases
Arrhenius bases typically exhibit the following characteristics:
- Bitter taste
- Slippery feel
- Ability to conduct electricity in aqueous solutions
- Ability to react with acids to produce water and a salt
- Ability to turn litmus paper blue
ii. Dissociation of Arrhenius Acids and Bases
When an Arrhenius acid dissolves in water, it dissociates to produce hydrogen ions (H+) and the anion of the acid. For example, hydrochloric acid (HCl) dissociates as follows:
HCl → H+ + Cl-
Similarly, when an Arrhenius base dissolves in water, it dissociates to produce hydroxide ions (OH-) and the cation of the base. For example, sodium hydroxide (NaOH) dissociates as follows:
NaOH → Na+ + OH-
The extent of dissociation of an acid or base is determined by its dissociation constant (Ka or Kb). A strong acid or base dissociates almost completely in water, while a weak acid or base dissociates only partially.
iii. Examples of Arrhenius Acids and Bases
Arrhenius acids and bases are ubiquitous in our daily lives. Here are a few common examples:
Arrhenius Acids:
- Hydrochloric acid (HCl) – used in household cleaners and for industrial purposes
- Sulfuric acid (H2SO4) – used in car batteries and fertilizers
- Nitric acid (HNO3) – used in the production of fertilizers and explosives
- Citric acid (C6H8O7) – found in citrus fruits and used as a food additive
- Acetic acid (C2H4O2) – found in vinegar and used as a preservative
Arrhenius Bases:
- Sodium hydroxide (NaOH) – used in soap and detergent production
- Potassium hydroxide (KOH) – used in fertilizers and as a catalyst
- Calcium hydroxide (Ca(OH)2) – used in construction materials and as a pesticide
- Magnesium hydroxide (Mg(OH)2) – used as an antacid and laxative
- Ammonia (NH3) – used in fertilizers and household cleaning products
Arrhenius acids and bases form the foundation of acid-base chemistry, providing a basic understanding of their characteristics and behaviors. By comprehending the dissociation of these substances in water, we gain insights into their role in various chemical reactions and processes. This knowledge serves as a stepping stone for exploring more advanced acid-base theories and their applications in various fields, including chemistry, biology, and environmental science.
