Untitled Quiz

Chemical Kinetics Key Concepts

• Average Rate of Appearance: Measures the change in concentration of a reactant or product over time, calculated as delta [B] / delta t.
• Rate Law: Describes the relationship between the rate of a reaction and the concentration of its reactants; expressed as Rate = k[A]^m[B]^n, where k is the rate constant and m, n are the reaction orders.
• First Order Reaction Differential Rate Law: For a reaction with first-order kinetics, the rate is proportional to the concentration of one reactant: Rate = k[A].

First Order Reaction Properties

• Integrated Rate Law: The concentration of a reactant over time can be related using the equation ln[A] sub t = -kT + ln[A] sub 0, demonstrating the logarithmic decrease in concentration.
• Half-Life: The time required for half of the reactant to be consumed in a first-order reaction is given by t sub 1/2 = 0.639/k, indicating that half-life is independent of the initial concentration.

Second Order Reaction Properties

• Second Order Reaction Differential Rate Law: For a reaction with second-order kinetics, the rate is proportional to the square of the concentration of one reactant: Rate = k[A]^2.
• Integrated Rate Law: The concentration for a second-order reaction over time can be determined by the equation 1/[A] sub t = kT + 1/[A] sub 0, revealing a linear relationship.
• Second-Order Half-Life: The half-life for a second-order reaction is calculated as t1/2 = 1 / k[A] sub 0, showing dependency on the initial concentration.

Energy and Activation Relations

• Fraction of Molecules with Energy ≥ Ea: Describes a fraction of molecules that possess energy greater than or equal to the activation energy: f = e^(-Ea/RT).
• Arrhenius Equation: Connects the rate constant (k) to temperature and activation energy, defined as K = A e^(-Ea/RT), where A is the pre-exponential factor.
• Calculating Activation Energy (Ea): By rearranging the Arrhenius equation, activation energy can be found from lnK = -Ea/RT + lnA, showcasing its relationship with the rate constant and temperature.

Slope and Temperature Relations

• Slope in Arrhenius Plot: The slope of the linear plot of ln(k) versus 1/T is represented as -Ea/R, where R is the universal gas constant.
• Change in Rate Constant with Temperature: To analyze the effect of two temperatures on the rate constant, use the equation ln(k2/k) = (Ea/R)(1/T1 - 1/T2), indicating how the rate constant varies with temperature changes.