System. surroundings. universe.thermodynamic state of a system.

– The number of moles and identity of each substance.– The physical states of each substance.– The temperature of the system.– The pressure of the system.

Thermochemical standard state conditions– The thermochemical standard T = 298.15 K.– The thermochemical standard P = 1.0000 atm.

• Be careful not to confuse these values with STP.Thermochemical standard states of matter

– For pure substances in their liquid or solid phase the standard state is the pure liquid or solid.

– For gases the standard state is the gas at 1.00 atm of pressure. For gaseous mixtures the partial pressure must be 1.00 atm.

– For aqueous solutions the standard state is 1.00 M concentration.State Functions are independent of pathway:

– T (temperature), P (pressure), V (volume), E (change in energy), H (change in enthalpy – the transfer of heat), and S (entropy)

Examples of non-state functions are:– n (moles), q (heat), w (work)

EntropyEnthalpyGibbs Free Energy

Heat, Latent Heat, Sensible HeatEnergyInternal energyKinetic EnergyPotential EnergyEndothermicExothermicThermodynamicsThermal EquilibriumSystemSurroundingsLaw of Conservation of EnergyLaw of Conservation of MassHeat Capacity, Molar Heat CapacitySpecific Heat CapacityFirst Law of Thermodynamics State FunctionStandard state temperatureStandard state pressureStandard states matterHess’s LawClosed SystemOpen SystemIsolated SystemHeat of FusionHeat of Vaporization

Specific Heat Capacity

How much energy is transferred due to Temperature difference?

The heat (q) “lost” or “gained” is related to

a) sample massb) change in T andc) specific heat capacity

Specific heat capacity = heat lost or gained by substance (J)(mass, g) (T change, K)

∆H = Hfinal - Hinitial

• The stoichiometric coefficients in thermochemical equations must be interpreted as numbers of moles. 1 mol of C5H12 reacts with 8 mol of O2 to produce 5 mol of CO2, 6 mol of H2O, and releasing 3523 kJ is referred to as one mole of reactions.

∆∆HHoorxnrxn = = ∆H ∆Hff

oo (prod) - (prod) - ∆H ∆Hff

oo (react)(react)

Specific heat capacity (J/(g∙K) =heat lost or gained by system (Joules)

mass(grams) T (Kelvins)

mTf –Ti)q

cP =

Variable System 1 System 2

Cp

Tf

Ti

m

q

heat transfer outheat transfer out(exothermic), -q(exothermic), -q

heat transfer inheat transfer in(endothermic), +q(endothermic), +q

SYSTEMSYSTEM

∆E = q + w

w transfer inw transfer in(+w)(+w)

w transfer outw transfer out(-w)(-w)

– The relationship describes the spontaneity of a system.• The relationship is a new state function, G, the Gibbs Free

Energy.• Sign conventions for G.

– G > 0 reaction is nonspontaneous– G = 0 system is at equilibrium– G < 0 reaction is spontaneous

G = H-TS at constant T and P

heat transfer outheat transfer out(exothermic), -q(exothermic), -q

heat transfer inheat transfer in(endothermic), +q(endothermic), +q

SYSTEMSYSTEM∆E = q + w

w transfer inw transfer in(+w)(+w)Compression of systemCompression of system

w transfer outw transfer out(-w)(-w)Expansion of systemExpansion of system

• Free energy has the relationship G = H -TS.

• Because 0 ≤ H ≥ 0 and 0 ≤ S ≥ 0, • there are four possibilities for G.

Forward reaction

H S G spontaneity< 0 > 0 < 0 at all T’s.< 0 < 0 T dependent at low T’s.> 0 > 0 T dependent at high T’s.> 0 < 0 > 0 Nonspontaneous at all T’s.

KineticsFour factors that affect the rate of reaction

nature of reactantconcentrationtemperaturepresence of a catalyst

Average rate

Rate of reactionRate constantOrder of reactantOverall order of reaction

Integrated rate laws ([ ] with respect to time)If zero order [A]0 - [A] = ak t

first order

second order

t d

D+

t c

C+or

t b

B-

t a

A-= Rate

k t aA

Aln 0

k t aA

1

A

1

0

General rate expression

Differential rate laws ([ ]with respect to rate)Rate = k [A]m[B]n[C]p

If zero order Rate = k[A]0 = k first order Rate = k[A]1 = k[A] second order Rate = k[A]2

•Change in rate is independent of the change in concentration of a zero order reactant•Change is rate is directly proportional to the change in concentration of a 1st order reactant•Change in rate is directly proportional to the square of the change in concentration of a 2nd order reactant

0 order[A] vs t

[A]

t

ln [A] vs t1st order

ln [A]

t

1/[A] vs t2nd order

1/[A]

t

Initial rateInstantaneous rate

Five factors that affect the rate of reaction:nature of reactantConcentrationTemperaturepresence of a catalystsolvent effects

Rate of reactionRate constantOrder of reactantOverall order of reaction

Substitute ½ [A]o for [A]In integrated rate law equation to get ½ life equation

All equations are shown for a stoichiometric coefficient of 1. for all others use the term akt, or ak in place of kt and k below.