Final answer:
A chemical reaction with low activation energy is most likely to occur, as it requires less energy to reach the transition state. Endergonic reactions and those with high activation energy are less likely to occur spontaneously. Enthalpy in the Gibbs free energy equation is denoted by ΔH. Therefore, correct option is b.
Step-by-step explanation:
The chemical reaction that is more likely to occur is b) A reaction with low activation energy. This is because a lower activation energy means that less energy is required for the reactants to achieve the transition state and proceed to products.
By contrast, an endergonic reaction (c) A reaction with a positive ΔG) or a reaction with high activation energy are less likely to occur spontaneously because they require an input of energy to proceed.
In terms of the Gibbs free energy equation, the term that denotes enthalpy is b. ΔH. When comparing endergonic and exergonic reactions, it's important to note that both types of reactions require some amount of energy to overcome a barrier, known as the activation energy.
However, the statement that the transition state exists at a lower energy level than the reactants is false. The transition state is at a higher energy level.
For example, Cellular respiration is an exergonic reaction as it releases energy, whereas Photosynthesis is endergonic as it requires energy input.
The presence of enzymes can decrease the activation energy of a reaction, making it more likely to occur by creating a lower energy pathway for the reaction.
This does not change whether the reaction is endergonic or exergonic, but simply lowers the energy barrier that must be overcome.