Arrhenius and Brønsted-Lowry Acids and Bases - 1.12.1

Acids and Bases (AQA)

In this course, Dr Nick Chatterton (Birkbeck College, University of London) covers various topics relating to acid-base chemistry in the AQA A-level specification. We begin by: (i) discussing the theories of acid and base behaviour, including Arrhenius and Bronsted-Lowry theories (Topic 1.12.1); and (ii) focusing on Lewis acid-base theory and the relative strength of acids and bases (Topics 1.12.1, 1.12.4); before (iii) explaining pH and concentration calculations for strong acids and bases (Topics 1.12.2, 1.12.3); and then (iv) covering weak acids and the equilibrium constant of water (Topics 1.12.3, 1.12.4); then (v) discussing titration curves and their four different types (Topic 1.12.5); before (vi) explaining the importance of buffers and how they maintain the pH of solutions (Topic 1.12.6); and finally (vii) providing examples of how to calculate the pH of buffer solutions using different experimental values (Topic 1.12.6).

Arrhenius and Brønsted-Lowry Acids and Bases - 1.12.1

In the first mini-lecture, we discuss the theories of acid and base behaviour (Topic 1.12.1). The lecture begins with the common acids and bases encountered in school, including bench acids like hydrochloric acid and functional group-containing molecules such as ethanoic acid. Arrhenius's early theory describes acids as substances that increase the concentration of hydrogen ions in water and bases as substances that release hydroxide ions. However, Bronsted and Lowry expanded on this theory to create a more general definition based on the movement of hydrogen ions in reactions. They defined acids as substances that donate hydrogen ions and bases as substances that accept hydrogen ions, and many acid-base reactions occur in equilibrium. Finally, the lecture explains the concept of conjugate acid-base pairs.