Outstanding overview of the conceptual heart of Chemical Thermodynamics.

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.

This discussion of gas-phase reactions provides a very good pathway to understanding how reactions progress towards the equilibrium state.