This book presents a modern new approach to studying chemical equilibria in aqueous solutions, offering a conceptually coherent and mathematically straightforward framework that simplifies complex topics such as Brønsted acid-base equilibria, solubility, and complexation, with a strong emphasis on real-world applications. Designed to suit various academic levels—from introductory biology to advanced chemistry—it is grounded in the Triad of Solution: matter balance, charge balance, and the law of mass action. The second part of the book explores advanced topics including recursive numerical methods, buffer capacity, solubility excess parameters, and pH calculations. Throughout, readers find numerous exercises and detailed solutions to reinforce understanding and support practical learning. 

Prof. André Fernando de Oliveira is a faculty member in the Department of Chemistry at the Universidade Federal de Viçosa (Brazil). His research focuses on the treatment of chemical data, including uni‑ and multivariate statistical approaches; the development, optimization, and validation of analytical methods; and sample pre‑treatment strategies. His work spans techniques such as spectrophotometry, potentiometry, voltammetry, gas chromatography, and high‑performance liquid chromatography. He also conducts research on equilibria in solution, including the development of the XXI Method. His book on this subject was selected as one of the finalists for the Jabuti Acadêmico Prize in the Chemistry/Materials category, the most prestigious literary award in Brazil.