Screencast 15.1
www.youtube.com/watch?v=DyK7cR0k3ds
This screencast walks you through the derivation of Equation 15.4.

Screencast 15.2
www.youtube.com/watch?v=tATSPjPDEc4
This screencast walks you through the butane/ methylpropane calculation.

Screencast 15.3
www.youtube.com/watch?v=78jaPMV4z7g
This screencast explains the graph in Figure 15.5 by walking you through the changes that happen when reactant or product is added to an equilibrium mixture.

Screencast 15.4
www.youtube.com/watch?v=6caqV49o1-M
This screencast walks you through the derivation of Equation 15.10 and shows how it is used to find ΔrH and ΔrS.