announcements reminder- exam #3 is one week from today (april 23 rd ) review session: wednesday,...
TRANSCRIPT
ANNOUNCEMENTSANNOUNCEMENTS•Reminder- Exam #3 is one week from today (April 23rd)
Review session: Wednesday, April 21st @ 5:00pm
When is the next exam?When is the next exam?
1 2 3 4
78%
16%
3%3%
1. One week from today
2. Two weeks from today
3. Next Wednesday
4. May 14th
The rate law for an elementary The rate law for an elementary step is given by the equation for step is given by the equation for that stepthat step
Elementary Step Molecularity Rate Equation
A → product Unimolecular Rate= k[A]
A + B → product Biomolecular Rate= k[A][B]
A + A → product Bimolecular Rate= k[A]2
2A + B → product Termolecular Rate= k[A]2[B]
Example: Ozone depletion by CFC’sExample: Ozone depletion by CFC’s
Cl + O3 → ClO + O2
ClO + O → Cl + O2
Overall reaction:Intermediate?Catalyst?
How to determine if a proposed reaction How to determine if a proposed reaction mechanism is “reasonable”mechanism is “reasonable” HH22 + 2ICl + 2ICl → → 2HCl + I2HCl + I22
Proposed mechanism 1:
Step 1:
H2 + ICl → HI + HCl (slow)
Step 2:
ICl + HCl → HI + Cl2
Sum
Rate
Step 1
Step 2
Overall
Proposed mechanism 2:
Step 1:
H2 + ICl → HCl + HI (slow)
Step 2:
HI+ ICl → HCl + I2
Sum
Rate
Step 1
Step 2
Overall
Two mechanisms for determining Two mechanisms for determining mechanismsmechanisms
1. Determine and interpret rate law
2. Isotopic Labeling
CHAPTER 15CHAPTER 15
EQUILIBRIA
Alcohols can be made from alkenes Alcohols can be made from alkenes and alkenes can be made from and alkenes can be made from alcoholsalcoholsAlkene→ Alcohol
Alcohol→ Alkene
Mechanism:
The principle of microscopic The principle of microscopic reversibilityreversibility
What is the equilibrium expression What is the equilibrium expression forfor Fe Fe22SS33(s) 2 Fe(s) 2 Fe3+3+(aq) + 3 (aq) + 3 SS2-2-(aq)(aq)
1 2 3 4
25% 25%25%25%1. 1:
2. 2:
3. 3:
4. 4:
][
]][[
32
23
SFe
SFeK
][
][][
32
3223
SFe
SFeK
]][[ 23 SFeK
3223 ][][ SFeK
Manipulating Equilibrium Expressions:
N2(g) + 3 H2(g) 2 NH3(g) K = =5.5 x 105
Reversing Reactions
Multiplying by a Factor
322
23
]][HN[
]NH[
Manipulating Equilibrium Expressions:
Adding Reactions
Cu(OH)2(s) Cu2+(aq) + 2 OH-(aq) K1 = 1.6x 10-19
Cu2+(aq) + 4 NH3(aq) Cu(NH3)42+(aq) K2 = 1.2 x 1012
Cu(OH)2(s) + 4 NH3(aq) Cu(NH3)42+(aq) + 2 OH-(aq) K = ?
Cu(NHCu(NH33))442+2+(aq) (aq) Cu Cu2+2+(aq) + 4 NH(aq) + 4 NH33(aq) K (aq) K
= 8.5 x 10 = 8.5 x 10-13-13
If [CuIf [Cu2+2+] = 1.0 x 10] = 1.0 x 10-6-6 , [NH , [NH33] = 1.0 x 10] = 1.0 x 10-3-3, , [Cu(NH[Cu(NH33))44
2+2+], then …], then …
1 2 3
33% 33%33%1. It is at equilibrium
2. Reaction goes forwards
3. Reaction goes backwards
Equilibrium Calculations: Your Pathway to Equilibrium Calculations: Your Pathway to HappinessHappiness
1. Write the equilibrium expression2. Determine Q
1. if Q = K, it’s at equilibrium2. if Q < K, reactants go to form products3. if Q > K, products go to form reactants
3. Call the amount reacting “x”4. Solve for x in the equilibrium expression5. Use x to determine equilibrium concentrations
Given these initial concentrations, what will the final concentrations be when equilibrium is reached?
K in terms of pressure: Kp vs. Kc
Kp = Kc(RT)n
n = change in numbers of moles of gas
2 NH3(g) N2(g) + 3 H2(g) Kc = 5.8 x 105
Kp =
LeChatelier’s Principle: Doing the math
1-Liter flask contains 0.50 mol butane and 1.25 mol isobutane (at equilibrium).
0.50 mol butane are added. What happens, and what is the result?