chemical equilibrium. the state of a chemical reaction in which its forward and reverse reactions...
DESCRIPTION
Law of Mass Action aA + bB + cC +... pP + qQ + rR +... Equilibrium Constant [P] p [Q] q [R] r... K = [A] a [B] b [C] c...TRANSCRIPT
![Page 1: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/1.jpg)
Chemical Equilibrium
![Page 2: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/2.jpg)
Chemical Equilibrium
The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the reactants and products does not change with time.
![Page 3: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/3.jpg)
Law of Mass Action
aA + bB + cC + ... <=> pP + qQ + rR + ...
Equilibrium Constant [P]p [Q]q [R]r ...
K = --------------------- [A]a [B]b [C]c ...
![Page 4: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/4.jpg)
![Page 5: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/5.jpg)
Meaning of Equilibrium Constant• K>>1: reaction is product-favored;
equilibrium concentrations of products are greater than equilibrium concentrations of reactants.
• K<<1: reaction is reactant-favored; equilibrium concentrations of reactants are greater than equilibrium concentrations of products.
![Page 6: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/6.jpg)
If K = 100 = [I2 in CCl4] / [I2 in water] for the equilibrium
I2 in water = I2 in CCl4
What is K for the reverse reaction, I2 in CCl4 = I2 in H2O?
100, 1, 0.01
![Page 7: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/7.jpg)
Acid-Base Equilibrium in Aqueous Solution
Acid Dissociation ConstantHC2H3O2 + H2O <=> H3O+ + C2H3O2
-
[H3O+][C2H3O2-]
K = ---------------------- [H2O][HC2H3O2]
[H3O+][C2H3O2-]
Ka = K*[H2O] = ---------------------- [HC2H3O2]
![Page 8: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/8.jpg)
Acid-Base Equilibrium in Aqueous Solution
Base Dissociation ConstantNH3 + H2O <=> NH4
+ + OH-
[NH4+][OH-]K = -----------------
[H2O][NH3] [NH4
+][OH-]Kb = K*[H2O] = ----------------
[NH3]
![Page 9: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/9.jpg)
Autoionization of Water
H2O + H2O <=> H3O+ + OH-
[H3O+][OH-]K = -----------------[H2O]2
Kw = K [H2O]2 = [H3O+][OH-] = 1.0 x 10-14
![Page 10: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/10.jpg)
Analogy in Semiconductors | | | |-Si:Si- <=> -Si+:Si- + e-
| | | |
| | -Si:Si- <=> h+ + e-
| |
K = h+ * e-
![Page 11: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/11.jpg)
e- and h+ in Semiconductors
SiSi
Si
SiSi
0 Kelvin
Si
Si Si
Si
Sie–
+h
room temperature
Production
Recombination
electrons (e )–
holes (h )+
Electron energy
conduction band
valence band
Si
Si SiSi SiSi
SiSiSi
SiSi SiSi
Si
e–
+h
Eg
conduction band
valence band
![Page 12: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/12.jpg)
Autoionization EquilibriaH:O:H H+ + OH–
Kw = [H+] [OH–]
—Si|
|:Si
|
|— —Si
|
|.Si
|
|— + e–
or
—Si|
|:Si
|
|— h+ + e–
K = [h+] [e–] = p n
10
10
10
10 6
10
14
18
0.001 0.002 0.003 0.004
GaAs
Si
Ge
water
400 200 100Temperature (°C)
0
1/T (Kelvin )–1
carr
ier
(h
or H
)
conc
entr
atio
n (c
m
)+
+–3
![Page 13: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/13.jpg)
e- and h+ in Semiconductors
+h
Si
Si SiSi SiSi
SiSiSi
SiSi SiSi
Si
e–+h
e–
(–)(+)
![Page 14: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/14.jpg)
Doping
Conduction Band
Donor Level
Valence Band
E
-
PSi Si
Si
Si+
(e )–
PSi Si
Si
Si
Addition of P to Si Addition of Al to Si
AlSi Si
Si
Si+
-(h )+
AlSi Si
Si
SiConduction Band
Acceptor Level
Valence Band
E
![Page 15: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/15.jpg)
Donors and Acceptors in Silicon
Ionization energy in parentheses (eV), measured from nearest band edge.
conduction band
acceptors M M + h+–}
valence band
donorsM M + e+ –}
00.10.20.3
0.50.4
0.30.4
0.20.10
0.5
In (0.16)–
Al (0.057)– Ga (0.065)–B (0.045)–
Sb (0.039)
+As (0.049)+P (0.044)+
Mn (0.53)+Cu –(0.49)
![Page 16: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/16.jpg)
Which dopant will act as an acceptor for Si?B, Ge, As
As a donor?B, Ge, As
![Page 17: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/17.jpg)
Fermi Level
fE fE
fE
fE
metal
p-typesemiconductor
undopedsemiconductor
n-typesemiconductor
The Fermi level is the energy at which the probability of finding an electron is 50%; below the Fermi level it is more likely that the electronic states are occupied with electrons and above the Fermi level it is more likely they are not occupied.
![Page 18: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/18.jpg)
Le Chatelier's Principle
If a stress, such as a change in concentration, pressure, temperature, etc., is applied to a system at equilibrium, the equilibrium will shift in such a way as to lessen the effect of the stress.
![Page 19: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/19.jpg)
Gas Phase Equilibrium
catalysis
N2(g) + 3 H2(g) <=====> 2 NH3(g) + heat high pressure and temperature
![Page 20: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/20.jpg)
![Page 21: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/21.jpg)
The Principle of Le Chatelier
Changes in Concentration or Partial Pressure
for N2(g) + 3 H2(g) 2 NH3(g)
an increase in N2 and/or H2 concentration or pressure, will cause the equilibrium to shift towards the production of NH3
![Page 22: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/22.jpg)
The Principle of Le Chatelier
Changes in Concentration or Partial Pressure
for N2(g) + 3 H2(g) 2 NH3(g)
likewise, a decrease in NH3 concentration or pressure will cause more NH3 to be produced
![Page 23: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/23.jpg)
The Principle of Le Chatelier
Changes in Temperature
for N2(g) + 3 H2(g) 2 NH3(g) + heat
for an exothermic reaction, an increase in temperature will cause the reaction to shift back towards reactants
![Page 24: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/24.jpg)
The cobalt complexes participating in the equilibrium below comprise a humidity sensor. From Le Châtelier's principle, when the sensor is moist (excess H2O), what color is the cobalt complex?
pink, blue
![Page 25: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/25.jpg)
A competition experiment involves O2 and CO vying for hemoglobin (Hb) sites, defined by the equilibrium
Hb(O2)4 + 4 CO = Hb(CO)4 + 4O2
From Le Châtelier's principle, how is CO poisoning reversed?
decrease O2 pressure, increase O2 pressure, remove Hb
![Page 26: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/26.jpg)
Heterogeneous Equilibrium
CaCO3(s) + heat <===> CaO(s) + CO2(g)
![Page 27: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/27.jpg)
Gibbs Free Energy and Equilibrium
G Reaction-------------------------------------Negative SpontaneousPositive Non-SpontaneousZero Equilibrium-------------------------------------
![Page 28: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/28.jpg)
The Influence of Temperature on Free EnergyG, H, & S
G = H - T S
H S G negative positive negative
spontaneous at all temperatures
![Page 29: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/29.jpg)
The Influence of Temperature on Free EnergyG, H, & S
G = H - T S
H S G positive negative positive
non-spontaneous at all temperatures
![Page 30: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/30.jpg)
The Influence of Temperature on Free EnergyG, H, & S
G = H - T S
H S G negative negative --------
spontaneous at low temperatures, nonspontaneous at high temperatures
![Page 31: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/31.jpg)
The Influence of Temperature on Free EnergyG, H, & S
G = H - T S
H S Gpositive positive --------
spontaneous at high temperatures, nonspontaneous at low temperatures
![Page 32: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/32.jpg)
Phase Transitions
H2O(s) -----> H2O(l) H > 0; S > 0
H2O(l) -----> H2O(g) H > 0; S > 0
spontaneous at high temperatures
![Page 33: Chemical Equilibrium. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the](https://reader035.vdocuments.us/reader035/viewer/2022062401/5a4d1b947f8b9ab0599c2a78/html5/thumbnails/33.jpg)
Phase Transitions
H2O(l) -----> H2O(s) H < 0; S < 0
H2O(g) -----> H2O(l) H < 0; S < 0
spontaneous at low temperatures