Outstanding overview of the conceptual heart of Chemical Thermodynamics.Chem1 Virtual Textbook - Chemical Energetics
Truly excellent survey of Thermochemistry. Before going deeper into Chemical Thermodynamics and Equilibrium, first make sure you understand Internal Energy change and Enthalpy change, the heart of Thermochemistry. A good understanding of Thermochemistry and Chemical Thermodynamics will make Biochemistry much easier and much more interesting.Purdue University - Gas-Phase Reactions
This discussion of gas-phase reactions provides a very good pathway to understanding how reactions progress towards the equilibrium state.