What is the unit of activation energy?

kJ mol^-1

The correct answer is option 2. \(\text{kJ mol}^{-1}\).

The unit of activation energy \((E_a)\) is typically expressed in joules (J) or kilojoules per mole (kJ/mol). Activation energy represents the minimum energy required for a chemical reaction to occur by overcoming the energy barrier between the reactants and the transition state. It is a measure of the energy difference between the reactants' energy and the highest energy point along the reaction pathway. While activation energy is commonly reported in joules or kilojoules per mole, it is important to note that other units such as calories (cal) or electronvolts \((eV)\) can also be used to represent activation energy, depending on the context and preference of the researcher or scientific community. Conversion factors can be applied to convert between different units if necessary.