The objective of this work is to illustrate several features of continuous-mixture kinetics for thermolytic and pyrolytic reactions. Cracking (bond scission) reactions occur during thermal decomposition (thermolytic) processes such as pyrolysis. We consider pyrolysis to be thermal decomposition of a solid material in contact with a gas. Such thermolysis usually results in a complex mixture of many products, which can often be described as a continuous function (frequency distribution) of a property, such as molecular weight. A population balance equation governs how the molecular-weight distribution (MWD) evolves in time and space. Continuous kinetics theories require the formulation of (1) a stoichiometric coefficient expression that shows how the products of scission are distributed, and (2) an expression for the rate coefficient indicating how the size of the cracking molecule affects the rate. This approach is herein applied to a pyrolytic reaction that yields tar with a measurable MWD and where char and gaseous products are lost from the reactor.