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To understand the collision model of chemical reactionsTo
understand activation energy To understand how a catalyst speeds up
a chemical reaction To explore reactions with reactants or products
in different phases To learn how equilibrium is established To
learn about the characteristics of chemical equilibrium Objectives
17.1Reaction Rates and EquilibriumEquilibrium1Big Idea 4Rates of
chemical reactions are determined by the details of the molecular
collisionsEquilibriumA. How Chemical Reactions Occur Collision
model molecules must collide in order for a reaction to occur Rate
depends on concentrations of reactants and temperature.
Equilibrium3A. How Chemical Reactions Occur Many reactions
proceed via a series of elementary reactionsElementary reactions
are mediated by collisions between molecules. Only collisions
having sufficient energy and relative orientation of reactants lead
to productsEquilibriumB. Conditions That Affect Reaction Rates
Concentration increases rate because more molecules lead to more
collisions Temperature increases rate Why?
Equilibrium5B. Conditions That Affect Reaction Rates Reaction
rates that depend on temperature and other environmental factors
are determined by measuring changes in concentrations of reactants
or products over timeEquilibriumB. Conditions That Affect Reaction
Rates Catalyst a substance that speeds up a reaction without being
consumed Enzyme catalyst in a biological system
Equilibrium8CatalystReaction rates may be increased by the
presence of a catalystCatalysts function by lowering the activation
energy of an elementary step in a reaction mechanism, and by
providing a new and faster reaction mechanismImportant classes in
catalyst include acid-base catalysis, surface catalysis, and enzyme
catalysisEquilibriumC. Heterogeneous Reactions Homogeneous reaction
all reactants and products are in one phase Gas Solution
Heterogeneous reaction reactants in two phases
Equilibrium10C. Heterogeneous Reactions
Equilibrium11D. The Equilibrium Condition Equilibrium the exact
balancing of two processes, one of which is the opposite of the
other
Equilibrium12D. The Equilibrium Condition Chemical equilibrium a
dynamic state where the concentrations of all reactants and
products remain constant
Equilibrium13E. Chemical Equilibrium: A Dynamic Condition
Equal numbers of moles of H2O and CO are mixed in a closed
container.
The reaction begins to occur, and some products (H2 and CO2) are
formed.
The reaction continues as time passes and more reactants are
changed to products.
Although time continues to pass, the numbers of reactant and
product molecules are the same as in (c). No further changes are
seen as time continues to pass. The system has reached
equilibrium.
Equilibrium14E. Chemical Equilibrium: A Dynamic Condition Why
does equilibrium occur?
Equilibrium15To understand the law of chemical equilibrium To
learn to calculate values for the equilibrium constant To
understand how the presence of solids or liquids affects the
equilibrium expression Objectives 17.2Characteristics of
EquilibriumEquilibrium16Big Idea 6Any bond or intermolecular
attraction that can be formed can be broken. These two processes
are in a dynamic competition, sensitive to initial conditions and
external perturbations.EquilibriumA. The Equilibrium Constant: An
Introduction Law of chemical equilibriumFor a reaction of the type
Each set of equilibrium concentrations is called an equilibrium
position. aA + bB cC + dD Equilibrium expression
Equilibrium18A. The Equilibrium Constant: An Introduction
Chemical equilibrium is a dynamic, reversible state in which rates
of opposing processes are equalSystems at equilibrium are
responsive to external perturbations, with the response leading to
a change in the composition of the systemEquilibriumB.
Heterogeneous Equilibria Heterogeneous equilibria an equilibrium
system where the products and reactants are not all in the same
state
Equilibrium20To learn to predict the changes that occur when a
system at equilibrium is disturbed To learn to calculate
equilibrium concentrations To learn to calculate the solubility
product of a salt To learn to calculate solubility from the
solubility product Objectives 17.3Applications of
EquilibriaEquilibrium21A. Le Chateliers Principle Le Chateliers
Principle when a change is imposed on a system at equilibrium the
position of the equilibrium shifts in a direction that tends to
reduce the effect of that change Equilibrium22A. Le Chateliers
Principle Effect of a Change in Concentration
Equilibrium23A. Le Chateliers Principle Effect of a Change in
Concentration When a reactant or product is added the system shifts
away from that added component. If a reactant or product is
removed, the system shifts toward the removed
component.Equilibrium24A. Le Chateliers Principle Effect of a
Change in Volume
The system is initially at equilibrium.
The piston is pushed in, decreasing the volume and increasing
the pressure. The system shifts in the direction that consumes CO2
molecules, lowering the pressure again.
Equilibrium25A. Le Chateliers Principle Effect of a Change in
Volume Decreasing the volumeThe system shifts in the direction that
gives the fewest number of gas molecules.
Equilibrium26A. Le Chateliers Principle Effect of a Change in
Volume Increasing the volume The system shifts in the direction
that increases its pressure. Equilibrium27A. Le Chateliers
Principle Effect of a Change in Temperature The value of K changes
with temperature. We can use this to predict the direction of this
change. Exothermic reaction produces heat (heat is a product)
Adding energy shifts the equilibrium to the left (away from the
heat term). Endothermic reaction absorbs energy (heat is a
reactant) Adding energy shifts the equilibrium to the right (away
from the heat term).
Equilibrium28B. Applications Involving the Equilibrium Constant
K > 1 the equilibrium position is far to the right K < 1 the
equilibrium position is far to the left The Meaning of K
Equilibrium29B. Applications Involving the Equilibrium Constant The
value of K for a system can be calculated from a known set of
equilibrium concentrations. Unknown equilibrium concentrations can
be calculated if the value of K and the remaining equilibrium
concentrations are known. Equilibrium30C. Solubility Equilibria The
equilibrium conditions also applies to a saturated solution
containing excess solid, MX(s). Ksp = [M+][X] = solubility product
constantThe value of the Ksp can be calculated from the measured
solubility of MX(s). Equilibrium31C. Solubility Equilibria Chemical
equilibrium plays an important role in acid-base chemistry and in
solubilityThe equilibrium constant is related to temperature and
the difference in Gibbs free energy between reactants and
productsEquilibrium