Final answer:
The energy of activation refers to the minimum energy needed to start a chemical reaction, leading to the transition state where bonds can break or form. Bond energy, measured in J/mol, is the energy required to break a chemical bond between two atoms. Activation energy is crucial for both exothermic and endothermic reactions to occur.
Step-by-step explanation:
The energy of activation is best described as the minimum amount of energy required to initiate a chemical reaction. This energy helps reactant molecules overcome energy barriers to reach a transition state, which is an intermediate state in which breaking and forming of bonds can occur, leading to the production of products. To quantify this, the term free energy of activation is used, which represents the usable energy required to bring molecules to the transition state at a given temperature.
Chemical bonds store energy, and breaking these bonds requires an input of energy known as bond energy. The bond energy is typically measured in joules per mole (J/mol) and represents the energy required to break a covalent bond between two atoms, a critical consideration in understanding chemical reactions. For instance, a C-C bond has a bond energy of about 80 kcal/mol, whereas a C=C bond is stronger, with a bond energy of about 145 kcal/mol.
The concept of activation energy is important because even exothermic reactions that release energy need this initial input of energy to get started. The energy supplied to reactant particles increases the likelihood of bond breakage when those particles collide, thus facilitating chemical reactions. Different chemical reactions require varying amounts of activation energy to proceed, which explains why some reactions occur spontaneously at room temperature while others need to be heated.