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ThermodynamicsDeals with energy changes and its flow from one system to

another

Explains why reactions occur

The universe is made up of system (reaction vessel) and

surroundings.

system energy

energymatter

matter

surroundings

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They occur by themselves without continuous

outside assistance

May continue only as long as it receives some

sort of outside assistance

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Thermodynamic Functions

Internal energy, (EEnthalpy, (H

Entropy, (S

Gibbs Free energy, (G

(E, (H, (S and (G are state functions

STATE FUNCTION

Depends only on the final state of thesystem and not on the path taken by the

system.

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Thermodynamic Functions

Internal Energy and Enthalpy

A change which lowers the energy of a system tends to

occur spontaneously.

(E = Efinal Einitial = q + w

q is the heat: absorbed (+) or evolved (-)

w is the work : done by the system (-), on the system (+)

W = - P(V ; (V = Vfinal Vinitial

Since PV = nRT for gases

W = (nRT ; (n = nproducts- nreactants

(H

=H

productsH

reactants =(

E + P(

V = qp

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Thermodynamic Functions

Entropy, (SDegree of disorder of a system

(S = Sfinal SinitialSsolid < Sliquid < Sgas

Spontaneous reactions tend to go towards maximumdisorder.

Gibbs Free Energy, (G(G = (H - T(S

(G < 0 reaction is spontaneous

(G > 0 reaction is non-spontaneous

(G = 0 reaction is at equilibrium

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Choose the substance with the higherentropy:

Solid CO2(dry ice) and gaseous CO

2

Predict the sign of the entropy change :

Sugar is added to a warm cup of coffee.

Iodine vapor condenses on a cold surface toform crystals.

Test yourself!

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Rates of Chemical Reactions

Collision TheoryReactants must collide to form products.Colliding units must be properly oriented

Colliding units must have sufficient energy to react.

Effective collisions make reactions possible.

Activation energy (Ea)Minimum energy that must be overcome to produce a chemical

reaction.

Transition state (T.S.)A structure which shows bond breaking and bond formation

Corresponds to the highest energy

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A + B

A----B

A

-B

E

Reaction progress

Ea

(T.S.)

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Factors influencing the rate of chemical

reactionsConcentration of reactants

The more reactants present, the more frequent collisions,

the faster is the reaction.

Surface areaThe greater the surface area exposed, the faster the reaction.

Temperature

The higher the T, the faster the reaction.

Catalyst

Accelerates a reaction by providing a pathway of loweractivation energy.

Not used up in the reaction.

Maybe of the same phase or different phase as the reactants.