differences between a photochemical reaction and a thermochemical reaction?
THERMOCHEMICAL REACTIONS :-
These reactions involve absorption or evolution of heat.
They can take place even in absence of light i.e. dark.
Temperature has significant effect on the rate of a thermochemical reaction.
The free energy change ∆G of a thermochemical reaction is always negative.
They are accelerated by the presence of a catalyst.
PHOTOCHEMICAL REACTIONS :-
These reactions involve absorption of light.
The presence of light is the primary requisite for the reaction to take place.
Temperature has very little effect on the rate of a photochemical reaction. Instead, the intensity of light has a marked effect on the rate of a photochemical reaction.
The free energy change ∆G of a photochemical reaction may not be negative.
Some of these are initiated by the presence of a photosensitizer. However a photosensitizer acts in a different way than a catalyst.