Why E Value to predict feasibility of redox is unreliable?

for the 1st Q:

E value is similar to ∆ H , they are taking the same things.
They provide only the next info:

1. whether the reaction is a reduction or oxidization

2. the amount of energy absorbed / released

We have to consider the most important factor,
that is to have an E value, the reaction should take place in advace.

With the help of a Energy diagram, we can know better.
That is we have to firstly come over the ENERGY BARRIER before the energy is released, no matter how great the amount.


2nd Q:

That is the similar question.
But it includes the concept of ENTROPY.

"This other type of energy is called entropy (S) and it is a measure of the randomness of a system. The second law of thermodynamics states that in spontaneous reaction, the entropy of the universe (which includes both the system and the surroundings) increases."

Therefore, We have to consider both entropy, and enthalpy (~E value) for the feasibility of a reaction.


Even the reaction is VERY exothermic, if the product is comparatively more orderless than the reactants (entropy decrease), we still cannot ensure the reaction can take place.