Chapter 10: Gases

Four essential gas laws establish quantitative relationships among pressure, volume, temperature, and the amount of substance: Boyle's law describes the inverse relationship between pressure and volume at constant temperature, Charles's law relates volume directly to absolute temperature, Avogadro's law connects volume to the number of moles, and the combined gas law unifies these relationships. These principles converge in the ideal-gas equation, PV equals nRT, which serves as the central mathematical framework for predicting gas behavior under various conditions, with careful attention to unit consistency for the gas constant R. Dalton's law of partial pressures explains how gas mixtures behave as independent components, with mole fraction providing a way to quantify individual gas contributions. Gas stoichiometry applies the ideal-gas equation to chemical reactions, enabling calculations of gas volumes produced or consumed. Kinetic-molecular theory provides the molecular-scale explanation for macroscopic gas behavior, linking temperature to the average kinetic energy of molecules and describing how molecular mass affects the velocity distribution of particles. The chapter explores effusion and diffusion processes, with Graham's law quantifying how different gases move at rates inversely proportional to the square root of their molar masses. Real gas behavior deviates from ideality due to intermolecular attractive forces and the actual volume occupied by gas molecules, phenomena captured by the van der Waals equation. These concepts have broad applications in respiratory physiology, atmospheric science, and industrial gas storage systems.