Introduction to Reaction Mechanisms - AP Chemistry

The minimum energy required to initiate a chemical reaction. Energy barrier that must be overcome for reaction to occur.

An assumption that the concentration of intermediates remains constant. Rate of formation equals rate of consumption for intermediates.

The rate constant of a reaction. Proportionality constant in rate law expressions.

Proper orientation during collisions is necessary for reaction. Molecules must collide with correct geometry for reaction.

Activation energy. Energy barrier parameter in temperature-dependent rate equation.

Higher collision frequency can increase the reaction rate. More collisions per unit time increases reaction probability.

$t_{1/2} = \frac{0.693}{k}$. Time required for concentration to decrease by half.

The universal gas constant. Fundamental constant linking energy and temperature scales.

An equation that relates the rate of reaction to the concentration of reactants. Mathematical expression relating reaction rate to concentrations.

To simplify the analysis of complex reaction mechanisms. Eliminates need to track rapidly changing intermediate concentrations.

A mechanism describing unimolecular reactions through a two-step process. Explains pressure dependence of unimolecular reaction rates.

Typically, $k$ increases with increasing temperature. Exponential relationship described by Arrhenius equation.

The detailed steps of how a reaction proceeds from reactants to products. Shows elementary steps connecting reactants to products.

Increased concentration generally increases reaction rate. More reactant molecules lead to more frequent collisions.

It limits the overall reaction rate. Slowest step controls overall reaction speed like bottleneck.

A reaction involving two reacting species. Has molecularity of two, most common elementary reaction type.

Catalysts are not consumed; intermediates are formed and consumed. Both help reaction proceed but have different consumption patterns.

An elementary reaction involving three molecules. Very rare due to low probability of three molecules colliding simultaneously.

$k = Ae^{-Ea/RT}$. Shows exponential dependence of rate constant on temperature.

$M^{-1}s^{-1}$. Units account for concentration dependence in second-order kinetics.

$8.314 J mol^{-1} K^{-1}$. Standard SI units for gas constant in energy calculations.

A reaction involving a single molecule undergoing change. Has molecularity of one and follows first-order kinetics.

A graph showing the energy changes during a reaction. Visualizes energy barriers and intermediates along reaction pathway.

Increasing temperature increases the reaction rate. Higher temperature increases molecular energy and collision frequency.

A substance that increases reaction rate without being consumed. Lowers activation energy by providing alternative pathway.

A catalyst lowers the activation energy of a reaction. Provides alternative pathway requiring less energy input.

$M s^{-1}$. Units reflect constant rate independent of concentration.

The slowest step in a reaction mechanism that determines the overall rate. Acts as bottleneck controlling overall reaction speed.

A high-energy, unstable arrangement of atoms at the peak of a reaction coordinate. Maximum energy point along reaction coordinate diagram.