h h c h
DESCRIPTION
H H C H. H H C H. Cl. H. OH. H H C H. Cl. H. OH. H H C H. Cl. H. OH. Cl. H. OH. H H C H. H H C H. OH. Cl. H. H H C H. Cl. HO. H. Cl. HO. H. H H C H. HO. H. Cl. KINETICS. - PowerPoint PPT PresentationTRANSCRIPT
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H
H C
H
OH
HCl
H
H C
H
OH HCl
H
H C
H
OH HCl
HCl
H
H C
H
OH
H
H C
H
OH HCl
Cl
H
H C
H
HHO
Cl
H
H C
H
HHO
Cl
H
H C
H
HHO
CHAPTER 9
REACTION
ENERGETICS
THER
MODYN
AMICS
THER
MODYN
AMICS
KINETICS
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STUDY OF RELATIONSHIP OFCHEMICAL REACTIONS AND THERMO DYNAMICS
1st LAW OF THERMODYNAMICS1st LAW OF THERMODYNAMICS1st LAW OF THERMODYNAMICSEuniv = E + Esur =
0E = - EsurEfinal - Einit
E HEAT ABSORBED BY SYSTEM+ WORK DONE ON SYSTEM
= = q + w q > 0, HEAT IS ABSORBEDq < 0, HEAT RELEASED
q > 0, ENDOTHERMIC q < 0, EXOTHERMIC
w > 0, WORK ON SYSTEMw < 0, WORK BY SYSTEM
ENERGY
CHEMISTRY
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MOST REACTIONS OCCUR AT CONSTANT TEMPERATUREAND PRESSURE .....BUT SOME ENERGY MAY BE LOST
HEAT OF REACTION
ENTHALPY, HCHANGE IN ENTHALPY, H:HEAT ABSORBED IN A REACTION CARRIED OUT AT CONSTANT PRESSURE
H:>0, REACTION ABSORBS HEAT ENDOTHERMIC
< 0, REACTION RELEASES HEAT EXOTHERMIC
IS A STATE FUNCTION!
PROPORTIONAL TO NUMBER OF MOLES
OPPOSITE SIGN FOR REVERSE REACTION
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Hcomb = HEAT ABSORBED WHEN 1 MOLE OF A
SUBSTANCE REACTS WITH OXYGEN AT CONSTANT P
C6H12O6 (s) + 6O2 (g) 6CO2 (g) + 6H2O (g) Hocomb = -2816 kJ
STANDARD STATEMOST STABLE FORM AT 1 atm AND THE SPECIFIED TEMPERATUREFOR DISSOLVED SUBSTANCE, 1 M
HOW MUCH HEAT IS RELEASED IF 10 g GLUCOSE IS BURNED?
H = -2816 kJ/mol x 0.056 mol = -157.7 kJ
mol glucose = 10 g x 1 mol/180 g = 0.056 mol
158 kJ of heat is released
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BOND ENERGY: ENERGY NEEDED TO BREAK 1 MOLE OF BONDS IN THE GASEOUS STATE
BREAKING: Ho : ALWAYS > 0
FORMATION Ho : ALWAYS < 0
ESTIMATE: Ho ~ BE BROKEN - BE FORMED
H2C=CH2 + HCl H3C-CH2Cl
1 x 612 1 x 431
1 C=C 1 H-Cl 1 C-H 1 C-Cl
TABLE 9.1
1 x 413 AND 1 x 234
Ho ~ 1043 - 647 = ~ 396 kJ/mol
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FOR A SPONTANEOUS PROCESS, SUNIV > 0
EVERY PROCESS INCREASES DISORDER IN THE UNIVERSE
S = qT AT WHICH HEAT IS ADDED
J/K
Sgas > Sliquid > Ssolution > Ssolid
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Suniv = Ssur + S
Suniv > 0
SPONTANEOUS SPONTANEOUS PROCESSPROCESS
NON-SPONTANEOUS NON-SPONTANEOUS PROCESSPROCESS
Suniv > 0 WHERE THE NUMBER OF
MOLES OF GAS INCREASES
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ESTIMATING ENTROPY CHANGE:
COMPARE PRODUCTS TO REACTANTS S
N2 (g) + 3H2 (g) 2NH3 (g) < 0
NaCl (s) Na1+ (aq) + Cl1- (aq) >0
CaCO3 (s) + H301+(aq) Ca2+ (aq) + 3H20 (l) + CO2 (g) >0
>0>0
< 0
~0
H20 (s) H20 (l) H20 (g)
CO2 @ 20 oC CO2 @ 0 oC
Ag (s) + NaCl (s) AgCl (s) + Na (s)
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Suniv = Ssur + S
AT CONSTANT P: Ssur = -H/T
-TSuniv = H - TSG
FOR A SPONTANEOUS REACTION:
Suniv > 0
G < 0
THE ENERGY OF THE PROCESS MUST DECREASE AND THE UNIVERSE MUST BECOME MORE RANDOM!!!!
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DRIVING FORCES FOR A CHEMICAL REACTION:
H -- ENERGY REQUIRED TO CHANGE TO POTENTIALENERGY OF REACTANTS TO THAT OF PRODUCTS
-TS -- ENERGY TO MAKE THE SYSTEM MORE ORDERED
H S SPONTANEOUS?
+ - NEVER - AT ANY T
+ + AT HIGH T
- - AT LOW T
RELATE TO G =H - TS <0
- + ALWAYS - AT ANY T
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WHAT IS POSSIBLE WHAT IS NOT POSSIBLE
WHAT HAPPENSHOW FAST IT HAPPENS
ENERGY DIFFERENCES ONLY!
CONCERNED WITH PATH
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CH3Br + OH 1-
POTENTIAL
E
CBr
H HH
OH-
TRANSITIONSTATE STERIC EFFECTS: MUST
HAVE PROPER ORIENTATION
H-O C OK
O-H C NR
E
Ea
MINIMUM AMOUNT OFENERGY FOR COLLISIONTO ACHIEVE TRANSITION
STATE
Ea(reverse)NEED COLLISION OF
PROPER ENERGY AND ORIENTATION FOR ELECTRONS
TO BE SHARED OR TRANSFERRED
CH3OH + Br 1-
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MOLL
SEC
FOR RATE OFAPPEARANCE
RATE SLOWS WITH TIMERELATED TO NUMBER OF REACTING PARTICLES
RATE OF DISAPPEARANCE
Rf = kf[A]X[B]Y
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IN IT’S SIMPLEST FORM: Rf = kf[A]X[B]Y
CH3Br + OH 1- <−> CH3OH + Br 1-
Rf = kf[CH3Br][OH1-]
N2 + 3H2 <−> 2NH3 Rf = kf[N2][H2]3
2NO2 <−> N2O4
HF (aq) + NH3 (g) <−> NH41+ (aq) + F1- (aq)
Rf = kf[NO2]2
Rf = kf[HF][NH3]
CATALYSTS & INHIBITORS
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H2 (g) + I2 (g) <−> 2HI (g) RATE 1 OR Rf
2HI (g) <−> H2 (g) + I2 (g)
H2 (g) + I2 (g) <−> 2HI (g)
RATE 2 OR Rr
Rf = Rr
K = = [HI]2
[H2][I2]Rf
Rr
[PRODUCTS] [REACTANTS]=
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K = [PRODUCTS] [REACTANTS]
F1- (aq) + HNO2 (aq) <−> HF (aq) + NO21- (aq)
K = ]HNO][F[
]NO][HF[
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[X] = MOLAR CONCENTRATIONS
2HCl (g) <−> H2 (g) + Cl2 (g)K =
)P(
PP2HCl
ClH 22
CAN ALSO USE CONCENTRATIONS
CaF2 (s) + 2H3O1+ (aq) <−> Ca2+ (aq) + 2HF (aq) + 2H2O (l)
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22
]OH[
]HF][Ca[K
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F1- (aq) + HNO2 (aq) <−> HF (aq) + NO21- (aq)
K = ]HNO][F[
]NO][HF[
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HCN (aq) + H2O (l) <−> CN1- (aq) + H3O1+ (aq)
]HCN[
]OH][CN[K
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1
K = [Pb2+][Br1-]2PbBr2 (s) <−> Pb2+ (aq) + 2Br1- (aq)SP
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K >> 1
Go = - RTlnK
EXTENSIVELARGE AMOUNT OF PRODUCT
EXOTHERMIC PROCESSES
K << 1NOT EXTENSIVESMALL AMOUNT OF PRODUCTENDOTHERMIC (IF NO CHANGE IN MOLE OF GAS INVOVED)
K VARIES ONLY WITH TEMPERATURE!!!!!!
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K = [PRODUCTS] [REACTANTS]
REACTANTS <−> PRODUCTS
LeCHATELIER’S PRINCIPLE:
A SYSTEM AT EQUILIBRIUM WILL RESPOND TO A STRESSIN A WAY TO MINIMIZE THE EFFECT OF THE STRESS
+ HEAT
ADD PRODUCT: FAVOR REACTANTS
ADD REACTANT: FAVOR PRODUCTS
DRIVE TO LEFT
DRIVE TO RIGHT