Chemistry - Reaction Rates and Equilibrium

rate

a measure of the speed of any change that occurs within an interval of time

reaction rate

amount of reactant changing per unit time

activation energy

the minimum energy needed to produce a reaction

activation complex

an unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier

transition state

the stage of a reaction when atoms have the highest energy

catalyst

A substance that speeds up a reaction, without being consumed itself in the reaction

enzyme

A large molecule (usually a protein) that catalyzes biological reactions

inhibitors

interfere with the action of a catalyst; reactions slow or even stop

Reversible Reactions

a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously

Le Chatelier’s principle

If stress is applied to a system in equilibrium, the system changes in a way that relieves the stress

concentration

adding more reactant produces more product, and removing the product as it forms will produce more product

temperature

increasing the temperature causes the equilibrium position to shift in the direction that absorbs heat

pressure

changes in pressure will only affect gaseous equilibria

K_eq

equilibrium constant

products

favored when K_eq > 1

reactants

favored when K_eq < 1

free energy

energy that is available to do work

spontaneous

reactions that actually occur involve processes that are ________

spontaneous reaction

• occurs naturally, and favors the formation of products at the specified conditions

• They produce substantial amounts of product at equilibrium, and release free energy

• will work by itself

non-spontaneous reaction

• a reaction that does not favor the formation of products at the specified conditions

• These do not give substantial amounts of product at equilibrium

entropy

measure of disorder (NO NEGATIVE VALUES)

law of disorder

the natural tendency is for systems to move to the direction of maximum disorder, not vice-versa

increase

An _______ in entropy favors the spontaneous chemical reaction

decrease

A _______ in entropy favors the non-spontaneous reaction

enthalapy

decreasing the energy in a system

H

enthalapy is represented by

S

entropy is represented by

negative

If ΔG is ______, the reaction is spontaneous.

positive

If ΔG is _______, the reaction is NOT spontaneous