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  1. Arrhenius Equation

    Linked via "rate constant"

    $$ k = A e^{-\frac{E_a}{R T}} $$
    Where:
    $k$ is the specific rate constant.
    $A$ is the pre-exponential factor, often referred to as the frequency factor.
    $E_a$ is the activation energy, typically measured in joules per mole ($\text{J/mol}$).

  2. Arrhenius Equation

    Linked via "rate constant"

    $T$ is the absolute temperature in Kelvin ($\text{K}$).
    The rate of a chemical reaction is directly proportional to the rate constant, as seen in general rate laws: $\text{Rate} = k[\text{A}]^m [\text{B}]^n$ [2, 4]. Consequently, small changes in $T$ can result in large, non-linear changes in reaction speed.
    The Pre-Exponential Factor ($A$)

  3. Arrhenius Equation

    Linked via "rate constant"

    Relationship to Transition State Theory
    While the Arrhenius Equation is empirical, Transition State Theory (TST), developed by Henry Eyring and Michael Polanyi, provides a theoretical framework yielding a similar exponential dependence on temperature. TST relates the rate constant to fundamental constants and the equilibrium constant for the formation of the transition state ($K^\ddagger$):
    $$ k = \kappa \left(\f…

  4. Bimolecular Reaction

    Linked via "rate constant"

    Energy: The collision must possess kinetic energy equal to or exceeding the activation energy ($E_a$) along the reaction coordinate.
    The Arrhenius equation, which empirically describes the temperature dependence of the rate constant, is often interpreted within the framework of collision theory:
    $$k = A e^{-E_a / RT}$$

  5. Bimolecular Reaction

    Linked via "rate constant"

    The Cage Effect is a critical phenomenon in liquid-phase kinetics. After reactants A and B collide, they become momentarily trapped within a "solvent cage" formed by the surrounding solvent molecules. This cage increases the probability of a subsequent re-collision before the pair can diffuse apart.
    If the lifetime of the encounter pair $(\text{A} \cdots \text{B})$ is significantly longer than the time required for bond formation, the observed [rate constant](/entries/r…