Reaction Kinetics and Potential Energy Diagrams

Vocabulary flashcards focusing on reaction kinetics, factors affecting reaction rates, collision theory, and potential energy diagrams.

Reaction Kinetics

The study of particle interactions during a chemical reaction ($RXN$).

Collision Theory

The theory stating that for any reaction to occur, reactant chemicals must collide with sufficient energy and with the proper or correct collision geometry.

Rate of Reaction

A measure proportional to the number of successful collisions per second (the frequency of successful collisions).

Maxwell-Boltzmann Distribution

A plot showing the fraction of collisions versus the energy of collisions, demonstrating how an increase in temperature provides more high-energy collisions that surpass the threshold energy barrier.

Threshold Energy Barrier

The minimum collision energy required on a Maxwell-Boltzmann distribution for collisions to be successful and allow reactants to form products.

Surface Area

A factor controlling reaction rate in heterogeneous reactions ($s+g$, $l+g$, $s+l$) where greater surface contact increases molecular collisions and successful collisions.

Concentration / Pressure

A factor where increasing the number of particles in a given volume of space or liquid increases particle collisions, successful collisions, and the reaction rate.

Catalyst

A substance that provides an alternate pathway (reaction mechanism) for reactants to form products, improving collision geometry and lowering the activation energy ($E_a$).

Nature of Reactants

The inherent chemical characteristics of reactants (such as bond type, polarity, solubility, or phase) that dictate how readily they collide and react.

Average Rate

A calculation of reaction rate determined by $\frac{\text{change in amount of reactant/product}}{\text{change in time}}$, representing an average rather than an instantaneous rate.

Potential Energy Diagram (PE Diagram)

A graphical representation of the potential energy of particles throughout the progress of a chemical reaction ($RXN$), assuming collision theory criteria are satisfied.

Activated Complex ($AC$)

A short-lived, highly unstable, high-energy transition molecule formed at the peak of the potential energy curve between reactants and products.

Activation Energy ($E_a$)

The minimum amount of collision energy required for reactant particles to reach the transition state and form products.

Enthalpy ($\text{Entholpy}$, $\text{Heat content}$, $\text{Symbol } riangle H$)

The net heat contained within particles during a reaction, defined as $\triangle H = PE_{\text{products}} - PE_{\text{reactants}}$ or $\triangle H = E_{af} - E_{ar}$.

Exothermic Reaction

A reaction with a net release of energy ($-\triangle H$) where the potential energy of reactants is greater than the potential energy of products ($R > P$).

Endothermic Reaction

A reaction with a net absorption of energy ($+\triangle H$) where the potential energy of products is greater than the potential energy of reactants ($P > R$).

Forward Activation Energy ($E_{af}$)

The energy difference between the activated complex ($AC$) and the reactants ($R$).

Reverse Activation Energy ($E_{ar}$)

The energy difference between the activated complex ($AC$) and the products ($P$).