Combustion Chemistry and Modeling, Henry Curran, Day 2 Part 1

This lecture, part of the Princeton-CEFRC Combustion Summer School, provides a comprehensive introduction to chemical kinetics, focusing on the determination of rate laws. The speaker, Henry Curran, begins by emphasizing the role of a kineticist in determining accurate rate constants. He explains the concept of reaction rate, using a specific bromine reaction to illustrate how rates can be expressed in terms of reactant consumption or product formation. The lecture then covers the general form of rate laws, emphasizing that reaction orders must be determined experimentally, not from stoichiometry. Several methods for determining rate laws are presented: the integration method (trial-and-error) for first and second-order reactions, the initial rates method, and the isolation or flooding method. For first-order reactions, the integrated rate law leads to a linear plot of ln[A] vs. time, and the half-life is independent of initial concentration. For second-order reactions, a plot of 1/[A] vs. time is linear, and the half-life depends on initial concentration. The initial rates method is demonstrated with a specific example (2NO + 2H2 → N2 + 2H2O), showing how varying one reactant’s concentration while keeping others constant allows determination of individual reaction orders. The lecture concludes with a brief discussion on measuring initial rates, using an analogy to illustrate the sensitivity of measuring small changes in reactants versus products.