Chapter 7:Chemical Reactions: Energy, Rates, and Equilibrium

Le Châteliers principle

states that when a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress.

→Gases

have more disorder and therefore higher entropy than liquids because particles in the gas move around more freely than particles in the liquid.

Le Châteliers principle

states that when a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress.

→Gases

have more disorder and therefore higher entropy than liquids because particles in the gas move around more freely than particles in the liquid.

non spontaneous reaction condition

A(n) positive value for ∆G means that free energy must be added and the process is nonspontaneous.

∆S

Conversely, has a negative value if the disorder of a system decreases.

catalyst

A(n) does not affect the energy level of either reactants or products.

chemical compounds

In , the attractive forces between ions or atoms are a form of potential energy.

spontaneous reaction conditio

A(n) negative for ∆G means that free energy is released and the reaction or process is spontaneous.

endothermic

A(n) chemical change that absorbs heat, like the breaking of bonds, is endothermic.

exothermic processes

For , heat is released (lost) and is indicated with a negative sign.

nonspontaneous process

A(n) requires continuous external influence and is endergonic; that is, free energy is added and it has a positive value of ∆G.

external assistance

A spontaneous process, once begun, proceeds without any and is exergonic; that is, free energy is released and it has a negative value of ∆G.

reverse reactions

When a reaction reaches equilibrium, the rates of the forward and are equal, and the concentrations of reactants and products remain constant.

external influence

A spontaneous process is one that, once started, proceeds on its own without any .

There are two fundamental kinds of energy

potential and kinetic

Two factors determine the spontaneity of a chemical or physical change

the release or absorption of heat, ∆H, and the increase or decrease in entropy, ∆S

K much smaller than 0.001

Only reactants are present at equilibrium; essentially no reaction occurs

K between 0.001 and 1

More reactants than products are present at equilibrium

K between 1 and 1000

More products than reactants are present at equilibrium

K much larger than 1000

Only products are present at equilibrium; reaction goes essentially to completion

potential energy

it is stored energy

kinetic energy

it is the energy of the motion

bond dissociation energy

amount of energy that must be absorbed to break the bond and separate the atoms in an isolated gaseous molecule.

heat of reaction

The difference between the heat energy absorbed in breaking bonds and the heat energy released in forming bonds

entropy

The amount of disorder in a system

activation energy

The amount of energy the colliding particles must have for productive collisions to occur