Kinetics for Quiz

rate

measure of the speed of any chance that occurs within an interval of time

reaction rate

change in concentration / time

collision theory

For a reaction to occur, the particles must collide, they must collide with the appropriate orientation, and they must collide with sufficient energy (called activation energy)

activated complex

an unstable arrangement of atoms that exists momentarily at the peak of the activation-energy barrier; an intermediate or transitional structure formed during the course of a reaction

activation energy

Energy needed to get a reaction started (space between activated complex and potential energy)

Inhibitor

A substance that slows down or stops a chemical reaction

Rate law

an expression relating the rate of a reaction to the concentration of the reactants

first order reaction

a reaction in which the reaction rate is proportional to the concentration of only one reactant (increase concentration by 2 increase reaction rate by 2)

second order reaction

a reaction whose rate depends on the concentration of one reactant raised to the second power or on the concentrations of two different reactants, each raised to the first power (increase concentration by 2 increase reaction rate by 4)

third order reaction

The rate is proportional to the cube of the concentration (increase concentration by 2 increase reaction rate by 8)

Overall order of reaction

The sum of the powers to which the concentration terms are raised in the rate equation

reaction mechanism

the step-by-step sequence of reactions by which the overall chemical change occurs

rate-limiting (rate-determining) step

the slowest step in a pathway

chemical equilibrium

In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time

K > 1

product favored

K < 1

reactant favored

K = 1

Reaction will reach equilibrium as an intermediate mixture, meaning the amounts of products and reactants will be about the same

LeChatelier's Principle

When a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress

Exothermic

Chemical Reaction in which energy is primarily given off in the form of heat

Endothermic

(of a chemical reaction or compound) occurring or formed with absorption of heat

spontaneous process

A process that occurs without an overall input of energy; a process that is energetically favorable

Entropy (∆S)

A measure of disorder or randomness

2nd law of thermodynamics

Every energy transfer or transformation increases the entropy of the universe

Enthalphy (ΔH)

heat

Gibbs free energy (G)

A measure of the spontaneity of a process

activated energy

= minimal requirement for "lift off"

reaction rates

speed at which things happen i

heterogeneous catalysts

catalysts that are in different phases than the reactants

inhibitors

prevent chemical reaction

elementary steps

intermediate products of chemical reactions

rate determining steps

the slowest intermediate reaction

intermediates

products produced before the final product and used up in a subsequent step

Heat of Reaction

the difference of Potential Energy between the Reactant(s) and Product(s)

Delta H

Change in heat, heat of reaction

Delta H = positive

endothermic

Delta H = negative

exothermic

endothermic

a positive change in heat

Exothermic

a negative change in heat

enzyme

protein catalyst that speeds up the rate of specific biological reactions

surface area

the sum of the areas of all the faces of a solid figure