Lesson 4: Acids and bases, Bronsted, Lewis acid and bases (Copy)

Acids and bases, Bronsted, Lewis acid & bases lecture

In Lesson 4, we focus on acids and bases, particularly through the lens of Brønsted-Lowry and Lewis definitions. We start by reviewing the fundamental concepts of acids and bases, emphasizing their importance in organic chemistry. The Brønsted-Lowry definition is introduced, where acids are proton donors and bases are proton acceptors, supported by common examples such as HCl (a strong acid) and NH3 (a base). We then explore the Lewis definition, which expands the concept by identifying acids as electron pair acceptors and bases as electron pair donors, illustrated with examples like BF3 (a Lewis acid) and OH- (a Lewis base).

We delve into the factors influencing the strength of acids and bases, such as electronegativity, atomic size, resonance stabilization, and inductive effects. This section includes practical examples to illustrate strong and weak acids and bases, helping students understand these concepts in context. The significance of pKa is explained, highlighting its role in determining acid strength, along with how to calculate and interpret pH values in various solutions.

The lesson also covers the mechanisms of acid-base reactions, using curved arrows to depict the movement of electrons during these reactions. We teach students how to predict the direction of acid-base reactions by comparing pKa values of the reactants and products. Throughout the lesson, students engage in practice problems to identify Brønsted-Lowry and Lewis acids and bases in reactions, calculate pH, and predict reaction outcomes.

In conclusion, we review the key concepts, ensuring a solid understanding of both Brønsted-Lowry and Lewis acids and bases, as well as the factors influencing their strength and reactivity. We also provide a brief overview of the next lesson, which will cover isomerism and stereochemistry. To reinforce learning, students complete targeted exercises and homework assignments focused on acid-base identification, pH calculation, and reaction prediction. This lesson equips students with a comprehensive understanding of acid-base chemistry, preparing them for more complex topics in organic chemistry.