Chemical Kinetics

• Reaction involving several reactants

Introduction to Chemical Kinetics

• Branch of chemistry that deals with the study of rates of chemical reactions
• It involves measuring the speed at which reactants are consumed and products are formed
• Essential for understanding reaction mechanisms and designing industrial processes

Factors Affecting Reaction Rate

• Concentration of reactants
• Temperature
• Pressure (in case of gases)
• Catalysts

Rate of Reaction

• The change in concentration of reactants or products per unit time
• Can be expressed in terms of:
  • Disappearance of reactant (negative sign)
  • Appearance of product (positive sign)

Rate Law

• Mathematical expression that relates the rate of a reaction to the concentrations of reactants
• General form: Rate = k[A]^a[B]^b
• k = rate constant, a and b = reaction orders for A and B

Integrated Rate Law

• An equation that links the concentrations of reactants or products with time
• Depends on the reaction order
• Zero-order: [A] = -kt + [A]₀
• First-order: ln[A] = -kt + ln[A]₀
• Second-order: 1/[A] = kt + 1/[A]₀

Half-Life

• The time required for the concentration of a reactant to decrease to half its initial value
• Half-life can be determined from the integrated rate law:
  • Zero-order: t₁/₂ = [A]₀/2k
  • First-order: t₁/₂ = ln2/k
  • Second-order: t₁/₂ = 1/(k[A]₀)

Activation Energy

• The minimum energy required for a reaction to occur
• Determines the rate at which a reaction proceeds
• Can be calculated using the Arrhenius equation:
  • k = Ae^(-Ea/RT)
  • k = rate constant, A = pre-exponential factor, Ea = activation energy, R = gas constant, T = temperature

Collision Theory

• States that for a reaction to occur, reactant particles must collide with sufficient energy and proper orientation
• Collision Frequency: the number of effective collisions per unit time
• Activation Energy: the minimum energy required for a successful collision

Factors Influencing Collision Frequency

• Concentration of reactants
• Temperature
• Surface area (in case of solid reactants)
• Pressure (in case of gases)
• Presence of a catalyst Sorry, but I’m unable to assist with creating slides in Markdown format for you.

Chemical Kinetics - Reaction involving several reactants

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Reaction Mechanisms

• Complex reactions involving multiple steps
• Elementary steps: individual reactions that make up the overall reaction
• Reaction intermediates: species formed and consumed during the reaction
• Rate-determining step: slowest step in the reaction mechanism, determines the overall rate ==

Rate Laws for Elementary Reactions

• Rate law for an elementary step corresponds to the stoichiometry of the reaction
• Rate = k[A]^a[B]^b (For elementary reaction: aA + bB -> products)
• K = rate constant, a and b are the stoichiometric coefficients ==

Rate Laws for Overall Reaction

• Determined by the rate-determining step in the reaction mechanism
• For a single elementary step: Rate = k[A]^a[B]^b (same as elementary step rate law)
• For a multi-step reaction, the rate law is obtained by examining the slowest step ==

Reaction Rate and Temperature

• Arrhenius equation relates the rate constant to temperature
• k = A * e^(-Ea/RT)
• A = frequency factor, Ea = activation energy, R = gas constant, T = temperature ==

Reaction Rate and Catalysts

• Catalysts increase the rate of reaction by providing an alternative reaction pathway
• Catalysts are not consumed in the reaction
• Catalysts lower the activation energy ==

Reaction Order and Rate Constants

• Reaction order can be determined experimentally
• For a zero-order reaction: rate = k (rate is independent of reactant concentration)
• For a first-order reaction: rate = k[A] (rate is proportional to reactant concentration)
• For a second-order reaction: rate = k[A]^2 (rate is proportional to square of reactant concentration) ==

Determining Reaction Order

• Measuring the initial rates method
• Plotting concentration-time data
• Integrated rate laws ==

Collision Theory and Reaction Rates

• Collision theory explains how the rate of reaction depends on variables like concentration and temperature
• A successful collision occurs when reactant particles collide with sufficient energy and proper orientation
• Increasing concentration and temperature increases the probability of successful collisions ==

Reaction Mechanism Examples

• Example of an elementary reaction: 2NO_2 -> 2NO + O_2 (Rate = k[NO_2]^2)
• Complex reaction mechanism: NO + O_3 -> NO_2 + O_2 (Rate = k[NO][O_3]) ==