Direction of thermodynamics

In a photosensitized reaction, radical induced isomerization can occur if the sensitizer undergoes either homolytic decomposition or hydrogen abstraction, or if the system contains impurities which give radicals on irradiation. The result may be to shift the measured photostationary state in the direction of thermodynamic equilibrium and to give anomalously high values of the quantum yields for cis-trans isomerization. 

This principle is quite general and quite versatile. It is worth keeping in mind to help you predict shifts in the direction of thermodynamic processes when various disturbances such as changes in temperature, pressure, or concentration are applied. 

To arrive at a solution for the dispersion law, entropy development during the diffusion process must be considered. This entropy develops over time as an exponential function approaching a saturation value. This behavior is characteristic of an irreversible process in the direction of thermodynamic equilibrium, and we are still in the thermodynamic branch. 

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