Based on their activation energies and energy changes and assuming that all collision factors are the same, rank the following reactions from slowest to fastest. (a) Ea = 45 kJ>mol; E = -25 kJ>mol (b) Ea = 35 kJ>mol; E = -10 kJ>mol (c) Ea = 55 kJ>mol; E = 10 kJ>mol

Verified step by step guidance

1. Understand the concept of activation energy (Ea) and its role in reaction rates. Activation energy is the minimum energy required for a reaction to occur. The higher the activation energy, the slower the reaction rate, assuming all other factors are constant.
2. Examine the given activation energies for each reaction. Reaction (a) has an Ea of 45 kJ/mol, reaction (b) has an Ea of 35 kJ/mol, and reaction (c) has an Ea of 55 kJ/mol.
3. Compare the activation energies to determine the relative speed of the reactions. Lower activation energies generally lead to faster reactions because less energy is required to reach the transition state.
4. Rank the reactions based on their activation energies from lowest to highest. Reaction (b) has the lowest activation energy, followed by reaction (a), and then reaction (c) has the highest.
5. Conclude that the reaction with the lowest activation energy (reaction b) is the fastest, followed by reaction (a), and the reaction with the highest activation energy (reaction c) is the slowest.

Key Concepts

Activation Energy (Ea)

Activation energy is the minimum energy required for a chemical reaction to occur. It represents the energy barrier that reactants must overcome to form products. A lower activation energy typically correlates with a faster reaction rate, as fewer energy collisions are needed to initiate the reaction.

Energy Change (E)

The energy change of a reaction, often denoted as ΔE, indicates the difference in energy between the reactants and products. A negative ΔE signifies an exothermic reaction, where energy is released, while a positive ΔE indicates an endothermic reaction, where energy is absorbed. This energy change can influence the reaction rate, but activation energy is the more critical factor.

Collision Theory

Collision theory states that for a reaction to occur, reactant particles must collide with sufficient energy and proper orientation. While the frequency and energy of collisions are essential, the activation energy determines how many of these collisions will lead to a successful reaction. Thus, understanding collision factors helps in ranking reaction rates based on their activation energies.