Pyrolysis experiments on n-hexadecane (n-C-16) were conducted at 673-723 K and n-C-16 concentrations of 0.07-1.47 mol/L by using batch type reactors. The main products of n-C-16 pyrolysis were n-alkanes and 1-alkenes at all the reaction conditions. The 1-alkene/n-alkane ratio decreased with increasing n-C-16 concentration at all the reaction temperatures. The rate of n-C-16 pyrolysis increased to a maximum and then decreased with increasing n-C-16 concentration. The activation energy of the overall rate constant of n-C-16 pyrolysis was 196 kJ/mol at 0.07 mol/L of n-C-16 concentration and 263 kJ/mol at 0.22 mol/L. To describe these phenomena, a mathematical model for the pyrolysis that expresses the radical network reaction, including initiation, isomerization, beta-scission, H abstraction, and termination, was developed. The effect of radical size-on the rates of bimolecular reactions (H abstraction and termination) was important for a correct quantitative description. Comparison between the experimental data and the model showed that the rates of bimolecular reactions were inversely proportional to the carbon number i of radical R-i. The model can predict product distribution and n-C-16 pyrolysis rate in a wide range of temperatures (603-893 K) and n-C-16 concentrations (6.86 x 10(-3) 2.48 mol/L). Furthermore, the model can describe the pyrolysis kinetics of n-C-10 - n-C-25 by considering the carbon number of the hydrocarbon.