5 - 1Chemistry for Allied Health: Equilibrium CHAPTER 9 Chemical Equilibrium Rates of Reaction...

5 - 1Chemistry for Allied Health: Equilibrium

CHAPTER 9CHAPTER 9Chemical EquilibriumChemical Equilibrium

Rates of ReactionRates of Reaction

EquilibriumEquilibrium


En

erg

y

Rxn Progress

2H2(g) + O2(g) 2H2O + Energy2H2(g) + O2(g) 2H2O + Energy

Just because something has the potential to reactJust because something has the potential to react doesn’t mean it will do so immediately.doesn’t mean it will do so immediately.Just because something has the potential to reactJust because something has the potential to react doesn’t mean it will do so immediately.doesn’t mean it will do so immediately.

HH2(g)2(g) + OO2(g)2(g) may may

stay together for stay together for

lifetime without lifetime without

reacting to form reacting to form

water.water.

HH2(g)2(g) + OO2(g)2(g) may may

stay together for stay together for

lifetime without lifetime without

reacting to form reacting to form

water.water.

Reaction RatesReaction Rates

Very stableproduct(H < 0)HH


Chemical kineticsChemical kineticsThe study of reaction rates (speed)The study of reaction rates (speed)

EnthalpyEnthalpy Only tell us if a reaction willwill && occur but not not how long it

will EntropyEntropy take.

KineticsKinetics Measures the time requiredtime required for a reaction to occur.


Chemical kineticsChemical kinetics

Kinetics of a chemical reaction can tell us -

how longhow long it will take for a reaction to reach completion.

how chemicals react to form products (mechanism(mechanism).

effects of catalystscatalysts and enzymes.

how to controlhow to control a reaction.


Speed at which reactant is used up.Speed at which product forms.

Oxidation: Paper burningburning Oxidation: Paper burningburning

Paper turning Paper turning yellowyellowPaper turning Paper turning yellowyellow

Oxidation: Nails rustingrustingOxidation: Nails rustingrusting


Fast:Fast:

Slow:Slow:


Figure 9.1Figure 9.1

Reaction RatesReaction RatesFast:Fast:

Slow:Slow:

Slower:Slower:


A reaction won’t happen if:A reaction won’t happen if:

Effective collisionsEffective collisions

Molecules are not alignedaligned correctly.

Insufficient energy to break bondsenergy to break bonds. N2 O2 N2 O2


3. They have to have enough E.

For reactants to make products:For reactants to make products:1. Molecules must collidecollide

(solvents really help)(solvents really help)

2. They have to be alignedaligned correctly.

(Parked cars don’t collide)(Parked cars don’t collide)

Effective collisionsEffective collisions


Activation EnergyActivation EnergyThe activation energyactivation energy Eact

Is the minimum energy needed for a reaction to take place upon proper collision of reactants.


Show the E duringa reaction.

Show the E duringa reaction.

Energy diagramsEnergy diagrams

HH

Activation energy

EEactact

En

erg

yA temporary state where bonds arereforming. Activated

Complex

ActivatedComplex


Factors Influencing Rxn RatesFactors Influencing Rxn RatesReaction rates can be affected by :Reaction rates can be affected by :

1. Reactant structure(polar vs. nonpolarpolar vs. nonpolar)• physical state of reactants

(vapor vs liqvapor vs liq.)2.2. ConcentrationConcentration of reactants

(medicationsmedications)• surface areasurface area (sugar cube vs crystalssugar cube vs crystals)

3.3. TemperatureTemperature (hypothermia & metabolismhypothermia & metabolism)

4.4. CatalystCatalyst (HH22OO22 & blood & blood)


IfIncrease reactant reactant

concentrationconcentrationthenthen

Increase # of collisions# of collisionsso so

Increase reaction ratereaction rate.


Concentration :Concentration :1.1. More Reactants:More Reactants:

More cars More cars More collisions More collisions



Concentration:Concentration:1.1. More Reactants:More Reactants:

8 blocks:8 blocks:34 surfaces34 surfaces

8 blocks:8 blocks:24 surfaces24 surfaces

More surface area More surface area More collisions More collisions



Temperature:Temperature:2.2. Higher Temperature:Higher Temperature:

Faster cars Faster cars More collisions More collisions

More Energy More Energy More collisions More collisions

Reacting molecules move faster,

providing colliding molecules w/ Eact.



Catalyst:Catalyst:3.3. Adding a Catalyst:Adding a Catalyst:

Lower ELower Eactact More collisions More collisions

Uncatalysed reactionUncatalysed reaction






Catalysed reactionCatalysed reaction

Lower activation energy

Alters reaction mechanism but not productsAlters reaction mechanism but not productsIs not used up during the reaction.Is not used up during the reaction.






Catalysed reactionCatalysed reaction

Lower activation energy

EnzymesEnzymes are biological catalysts.EnzymesEnzymes are biological catalysts.


Catalytic ConverterCatalytic Converter


Catalytic ConverterCatalytic Converter


EquilibriumEquilibriumA state where the forward and reverse

conditions occur at the same rate.

DynamicEquilibrium

I’m in staticequilibrium.


Chemical equilibriumChemical equilibriumDynamic processDynamic process Rate of forward Rxn = Rate of reverse RxnRate of forward Rxn = Rate of reverse Rxn

HH22OO(l) (l) HH22OO((g)g)

(reactant) (product)(reactant) (product)

DynamicEquilibriumConcentration of reactants Concentration of reactants

and products remain constantand products remain constant over time.over time.


Equilibrium andEquilibrium andreaction ratesreaction rates

A point is ultimatelyreached where therates of the forwardrates of the forwardand reverse reactionsand reverse reactionsare the same.are the same.

At this point, equilibrium is achieved.

Rea

ctio

n r

ate

Time

HH22OO(l)(l) H H22OO(g)(g)

(reactant) (product)(reactant) (product)



2SO2(g) + O2(g) 2SO3(g)

At Equilibium

SO2(g)+O2(g)

Initially

SO3(g)

Initially



2SO2(g) + O2(g) 2SO3(g)

At Equilibium

SO2(g)+O2(g)

Initially

SO3(g)

Initially



N2(g) + O2(g) 2NO(g)

At Equilibium

N2(g)+O2(g)

Initially

NO(g)

Initially


EquilibriumEquilibriumC

on

cen

trat

ion

Time

Kinetic EquilibriumRegion Region

CConcentration of oncentration of reactants and products reactants and products remain constantremain constant over time. over time.


[C]c [D]d

[A]a [B]bKeq =

Equilibrium constant (K)Equilibrium constant (K)

Equilibrium expressionEquilibrium expression (for any reaction at constant

temperature)aA + bB cC + dD

moles per litermoles per liter

coefficients

productsreactants



[C]c [D]d

[A]a [B]bKeq =

aA + bB cC + dDproductsreactants



N2(g) + 3 H2(g) 2 NH3(g)

Keq = [ NH3 ] 2

[ N2 ] [ H2 ] 3



Le Chatelier’s principleLe Chatelier’s principle

Stress causesStress causes shift shift in equilibriumin equilibrium

Adding or removing reagent

N2(g) + 3 H2(g) 2 NH3(g)

Stress causesStress causes shift shift in equilibriumin equilibrium


N2(g) + 3 H2(g) 2 NH3(g)

Add moreN2?

NN22

Reaction shifts to the right[NH3] inc, [H2] dec




N2(g) + 3 H2(g) 2 NH3(g)


N2(g) + 3 H2(g) 2 NH3(g)

Add moreNH3?

NHNH33

Reaction shifts to the left[NN22] and [H2] inc



Adding Pressure affects an equilibrium with gases

N2(g) + 3 H2(g) 2 NH3(g)

Add PP?

Increasing pressure causes the equilibrium to shift to the side with the least moles of gas.

4 mol

of reactants

2 molof products



Temperature can also have an effect.

For exothermicexothermic reactions

reactants products + heatreactants products + heat

Raising the temperature shifts it to the left.

For endothermicendothermic reactions

heat + reactants productsheat + reactants products

Raising the temperature shifts it to the right.


FeClFeCl33 + 3NH+ 3NH44CNSCNS Fe(CNS)Fe(CNS)33 + + 3NH3NH44ClClYellowYellow RedRed

1. What happens when FeClFeCl33 is added ?2. What happens when NHNH44CNS CNS is added ?3. What happens when Fe(CNS)Fe(CNS)33 is removed ?







ExampleExampleOO22 transport in blood transport in blood

Equilibrium equationEquilibrium equation

HbHb + 4 OO22 Hb(OHb(O22))44

lungs = abundance of Oabundance of O22 :lungs = abundance of Oabundance of O22 :

IncInc

Cells = lack of Olack of O22 :Cells = lack of Olack of O22 :

DecDec



Equilibrium equationEquilibrium equation

HbHb + 4 OO22 Hb(OHb(O22))44

Equilibrium expressionEquilibrium expression

KKHbHb = = [Hb(O[Hb(O22))44]]

[Hb][Hb] [O[O22]]44


lungslungs = = abundance of Oabundance of O22 : :


HbHb + 4 + 4 OO22 Hb(OHb(O22))44

HbHb + 4+ 4 OO22 Hb(OHb(O22))44

Cells =Cells = lack of Olack of O22 : :

Oxygen is given up by the hemoglobinOxygen is given up by the hemoglobin..

OxygenOxygen is picked up by the is picked up by the hemoglobin.hemoglobin.

(Hypoxia) :(Hypoxia) :

50% more 50% more red blood cellsred blood cells in persons in persons living at high altidudes.living at high altidudes.

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5 - 1Chemistry for Allied Health: Equilibrium CHAPTER 9 Chemical Equilibrium Rates of Reaction...

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