Free the energy!
The free energy change of a chemical reaction can help determine whether a reaction is spontaneous at a certain temperature, i.e. whether the reaction will go forth. If the free energy change of a reaction is negative, then the reaction is spontaneous.
Is it possible for a reaction to have a negative free energy change at a certain temperature but not have the reaction occur to any measurable degree?
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1 solution
While the free energy change may say that the reaction should go forth, we still have to consider kinetics. Recall that all reactions require a certain amount of activation energy in order to happen. If the reactants at a certain temperature do not possess enough kinetic energy to surpass this amount, then the reaction will not occur. One example is the synthesis of ammonia gas, NH 3 , from nitrogen and hydrogen gas. Free energy calculations tell us that the reaction should be spontaneous at relatively low temperatures. However, at these temperatures, the molecules of nitrogen and hydrogen gas do not have enough kinetic energy and do not collide with each other fast enough to get over the activation energy "hump" and kickstart the reaction. So the reaction does not produce any measurable amount of ammonia.
Therefore, we conclude that yes , it is possible for a reaction with negative free energy change to not occur to any measurable degree.