Chapter 16: Chemical Kinetics
16.1: Reaction Rates
- Kinetics
- The study of the rates of chemical reactions and the steps by which they occur.
- Reaction Rate
- A measure of how quickly reactants change into products, typically expressed in moles per liter per second.
- Activation Energy (Ea)
- The minimum energy necessary for a chemical reaction to occur.
- Effective Collision
- A collision between reactants with sufficient energy and proper orientation to cause a reaction.
Factors Affecting Reaction Rates
- Nature of Reactants: Reactivity varies based on the type and combination of elements.
- Concentration: Higher concentrations increase the likelihood of collisions.
- Temperature: Reaction rate increases as temperature increases due to higher particle energy.
- Surface Area: Greater surface area allows more collisions to occur.
- Presence of Catalysts: Catalysts lower activation energy, speeding up reactions.
Collision Theory
- For a reaction to occur, particles must collide.
- Collisions must have proper orientation for bond rearrangement.
- Collisions must be sufficiently energetic to overcome activation energy.
Energy Diagrams
- Exothermic Reactions: Reactants have more energy than products; energy is released.
- Endothermic Reactions: Reactants have less energy than products; energy is absorbed.
- The highest point on the diagram represents the activation energy needed for the reaction.
Catalysts
- Catalyst
- A substance that changes a reaction's rate without being consumed.
- Homogeneous Catalyst
- A catalyst in the same phase as the reactants.
- Heterogeneous Catalyst
- A catalyst in a different phase than the reactants.
- Enzyme
- A naturally occurring biochemical catalyst.
- Inhibitor
- A substance that reduces the effectiveness of a catalyst, slowing its action.
Questions for Students
- Define kinetics and explain its role in chemical reactions.
- What is activation energy, and why is it important in chemical reactions?
- Describe the three conditions necessary for a reaction to occur according to collision theory.
- List and explain five factors that affect reaction rates.
- What is the difference between a homogeneous catalyst and a heterogeneous catalyst?