Chemical Kinetics

Kinetics

Study of the rates of reactions and the steps by which the occur

Endothermic

Pertaining to a chemical process that absorbs heat energy and produces positive change in enthalpy

Exothermic

Pertaining to a chemical process that releases heat energy and produces a negative change in enthalpy

Collision Theory Rule 1

Particles must collide before they can react. However, a collision alone doesn’t guarantee a reaction

Collision Theory Rule 2

Be properly oriented for the necessary rearrangement of atoms and electrons

Collision Theory Rule 3

Be forceful enough/possess enough energy to form products. Reactions follow only forceful, oriented collisions

Activation energy

Minimum amount of kinetic energy that must be possessed by the colliding molecules before they react

Activated complex

Colliding reactants that form a theoretical, transitional structure between reactant and product

Reaction rates

tell how fast reactions change into products

Factors that affect reaction rates

Nature of reactants, concentration, temperature, surface area, and presence of catalysts

Nature of reactants

This controls the rate of the reaction. Reactive substances react quickly and vice versa. Some noble gases never react or barely do. Another variable is combination, H and Cl under certain conditions react vigorously.

Concentration

This increases the rate of a reaction. Varies from reaction to reaction, it could double or even quadruple the rate

Temperature

Reaction rates double for every 10 C in temperature. Higher temperatures increase number of collisions and the force of collisions

Surface area

If a substance is broken up into smaller pieces more surface area is exposed causing it to react faster.

Catalysts

A substance that changes a reaction rate without being permanently changed or consumed by the reaction. Has lower activation energy

Enzymes

A class of catalysts that are naturally occurring biological substances

Homogeneous catalyst

in the same phase as the reactants or in solution with a reactant

Heterogeneous catalyst

a catalyst in a separate phase than the reactant

Inhibitor

A substance used to reduce a catalysts undesirable effects.