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Exploring from water: Why are the reactions between acids and bases so amazing?
The reaction of acids and bases is not only basic knowledge in chemistry, but also a common phenomenon in life. We often find that acids and alkalis are everywhere, whether in the ingredients in the kitchen or in the ingredients of detergents. Through the evolution of modern chemical theory, especially the Brønsted-Lowry acid-base theory, we can gain a deeper understanding of the nature of these reactions and the wonderful processes that occur in water.
Basic concepts of Brønsted-Lowry theory
Brønsted-Lowry theory was independently proposed in 1923 by Johannes Nicholas Brønsted and Thomas Martin Lowry. A basic idea of this theory is that when an acid and a base interact, the acid will release a proton (H+), and the base will accept this proton to form their respective conjugate base and conjugate acid.
Acid + Base ⇌ Conjugate Base + Conjugate Acid
Definition of acids and bases
According to Arrhenius theory, acids can be defined as substances that release hydrogen ions (H+) in aqueous solutions, while bases are substances that release hydroxide ions (OH−). In Brønsted-Lowry theory, acids and bases are defined in terms of their interactions. This means that under certain circumstances, the same substance can act as both an acid and a base.
Acid-base reaction in aqueous phase
Consider a common example of an acid-base reaction: the reaction between acetic acid (CH3COOH) and water (H2O). In this reaction, acetic acid acts as an acid and releases a proton to form the conjugate base acetate ion (CH3COO−) and the conjugate acid hydroxide ion (H3O+).
CH3COOH + H2O ⇌ CH3COO− + H3O+
Characteristics of amphoteric substances
Water is an amphiphilic substance, meaning it can act as both an acid and a base. This shows us the relative relationship between acids and bases. Such characteristics allow many substances to exhibit different behaviors in different environments. For example, aluminum hydroxide (Al(OH)3) can also be used as an acid or base. In different reactions, its role changes depending on the reactants.
Acid-base reactions in non-aqueous solutions
Similar acid-base reactions also exist in non-aqueous solutions, such as liquid ammonia (NH3). In liquid ammonia, interactions between ammonia molecules can also allow one ammonia molecule to act as an acid and the other as a base. This allows the properties of acids and bases to still be displayed in non-aqueous environments, showing the broad applicability of the Brønsted-Lowry theory.
Comparison between Brønsted-Lowry theory and Lewis theory
It is worth mentioning that the Lewis theory, which appeared at the same time as the Brønsted-Lowry theory, was mainly based on electronic structure and focused chemical reactions on the transfer of electron pairs. Lewis acid is a substance that can accept electron pairs, while Lewis base is a substance that can donate electron pairs. These two theories are not contradictory in their understanding of the nature of acid-base reactions and can complement each other.
Conclusion
By studying the Brønsted-Lowry theory, we realize that the interaction between acids and bases is not a simple reaction, but a dynamic interaction. These reactions not only occur in water, but also in other solvents, revealing the complexity and wonder of the chemical world. Against this background of knowledge, will readers rethink those seemingly ordinary chemical reactions in daily life?
