Question

Why don't all thermodynamically favored reactions occur rapidly?

Answer 1

solution:

Thermodynamically favorable reaction is the products, because the reaction occurs spontaneously, without the need for energy to be added.

Because a reaction is thermodynamically favoured does not mean that it will be a fast reaction. So 'yes' they always proceed but possibly infinitesimally slowly. Temperature is the most common way of quickening a reaction. Of course a catalyst also does so but this generally by changing the way the reaction occurs, i.e. the mechanism is different using a catalyst but the product is the same. Enzymes are natures catalysts, in synthetic chemistry (and in you car exhaust) metal based compounds are often used.

All reactions have an activation energy EaEa between reactants and products and a small increase in the size of this can slow a reaction exponentially. Experimentally, the rate constant is generally found be of the form k=k0exp(−Ea/RT)k=k0exp(−Ea/RT), which is the Arrhenius equation, with R the gas constant and T the temperature in Kelvin .