Chemical Kinetics

Key Concepts

• Chemical Kinetics: Study of reaction rates and mechanisms.
• Thermodynamics: Predicts feasibility of a reaction (ΔG < 0).
• Chemical Equilibrium: Determines the extent of a reaction.
• Reaction Rate: Influenced by concentration, temperature, and catalysts.
• Rate of Reaction: Can be average or instantaneous.

Rate of Reaction

• Average Rate: Depends on change in concentration over a time interval.
  • Formula: [ \text{Rate} = \frac{\Delta [R]}{\Delta t} ]
• Instantaneous Rate: Rate at a specific instant, determined by tangent slope on concentration vs. time graph.
  • Formula: [ r_{inst} = \lim_{\Delta t \to 0} \frac{d[R]}{dt} ]

Reaction Order and Rate Law

• Rate Law: Relates rate to concentration of reactants.
  • Formula: [ \text{Rate} = k[A]^x[B]^y ]
• Order of Reaction: Sum of the powers of concentration terms in rate law.
• Molecularity: Number of molecules involved in an elementary step.

Factors Influencing Reaction Rate

• Concentration: Increasing concentration generally increases the rate.
• Temperature: Rate increases with temperature; explained by Arrhenius equation.
  • [ k = Ae^{-Ea/RT} ] where A is frequency factor, Ea is activation energy.

Integrated Rate Equations

• Zero Order Reaction: Rate is constant.
  • [ [R] = -kt + [R]_0 ]
• First Order Reaction: Rate depends on concentration of one reactant.
  • [ \ln[R] = -kt + \ln[R]_0 ]

Half-Life of Reactions

• Zero Order: [ t_{1/2} = \frac{[R]_0}{2k} ]
• First Order: [ t_{1/2} = \frac{0.693}{k} ]

Temperature Dependence

• Arrhenius Equation: Describes how rate constant changes with temperature.
  • Graph of ( \ln k ) vs ( 1/T ) is a straight line.

Collision Theory

• Effective Collisions: Require proper orientation and sufficient energy.
• Steric Factor (P): Accounts for orientation in collisions.

Catalysts

• Catalyst: Substance that increases reaction rate without being consumed.
• Lowers activation energy, providing an alternate pathway.

Summary

• Study of kinetics: Essential to understand reaction dynamics and control processes.
• Rate equations: Must be determined experimentally.

Exercises

• Various exercises and example problems provided for practical understanding of concepts like rate laws, order of reaction, and temperature effects on reaction rates.

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These notes cover the fundamental concepts of chemical kinetics as discussed in the provided lecture transcript. They include definitions, formulas, and examples to facilitate understanding and application of chemical kinetics principles.