Drill:

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Drill:•List five factors & explain how each affect reaction rates

Review Drill&

Check HW

CHM II HW• Review PP-19 & 20

• Complete the attached worksheet & turn it in tomorrow

• Lab Thursday

Chemical Equilibria

Equilibrium•The point at which the

rate of a forward reaction = the rate of its

reverse reaction

Equilibrium•The concentration of all

reactants & products become constant at

equilibrium

Equilibrium• Because concentrations

become constant, equilibrium is sometimes

called steady state

Equilibrium•Reactions do not stop at

equilibrium, forward & reverse reaction rates

become equal

Reaction• aA(aq)+ bB(aq) pP(aq)+ qQ(aq)

• Ratef = kf[A]a[B]b

• Rater = kr[P]p[Q]q

• At equilibrium, Ratef = Rater

• kf[A]a[B]b = kr[P]p[Q]q

At equilibrium, Ratef = Rater

kf[A]a[B]b = kr[P]p[Q]q

kf /kr = ([P]p[Q]q)/ ( [A]a[B]b)

kf /kr = Kc = Keq in terms of concentrationKc = ([P]p[Q]q)/ ( [A]a[B]b)

All Aqueous

aA + bB pP + qQ

aA + bB(g) pP + qQ

Equilibrium Expression

( Products)p

(Reactants)rKeq=

Drill: Solve Rate Expr:

X + Y M + N fast

3M + N 2G fast

2N K fast

2G + K Prod. slow

X + Y M + N fast

3M + N 2G fast

2N K fast

2G + K Prod. slow

Work from the slow step up

X + Y M + N fast

3M + N 2G fast

2N K fast

2G + K Prod. slow

1) Cancel K & G

X + Y M + N fast

3M + N 2G fast

2N K fast

2G + K Prod. slow

1) Cancel K & GTriple rxn 1 &

cancel

3X + 3Y 3M + 3N

3M + N 2G fast

2N K fast

2G + K Prod. slow

Solve Rate Law

A + B C + D fast

4 C + A 2G fast

2 K 4D + B fast

G + K 2 Q + 2 W fast

Q + W Prod. slow

Drill: Solve Rate LawA + B C + D fast

4 C + A 2G fast

2 K 4D + B fast

Q + W Prod. slow

1) Reverse step 3

4 C + A 2G fast

4 D + B 2K fast

Q + W Prod. slow

1)Reverse Rxn 3Divide Rxn 4 by 2 & cancel

4 C + A 2G fast

4 D + B 2K fast

G/2 + K/2 Q + W fast

Q + W Prod. slow

1) Reverse Rxn 3Divide Rxn 4 by 2 & cancelDivide Rxns 2 & 3 by 4 & cancel

C + A/4 G/2 fast

D + B/4 K/2 fast

G/2 + K/2 Q + W fast

Q + W Prod. slow

1) Reverse Rxn 3Divide Rxn 4 by 2 & cancelDivide Rxns 2 & 3 by 4 & cancelAdd the rxns

5/4 A + 5/4 B Product

Rate = k[A]5/4[B]5/4

Review & Collect Drill

CHM II HW•Review PP-19 & 20

•Remember M. S.

Equilibrium Applications

•When K >1, [P] > [R]

•When K <1, [P] < [R]

Equilibrium Calculations

Kp = Kc(RT)ngas

Equilibrium Expression

•Reactants or products not in the same phase are not included in the equilibrium expression

Equilibrium ExpressionaA(s)+ bB(aq) cC(aq)+ dD(aq)

[C]c [D]d

[B]b Keq=

Reaction Mechanism• When one of the

intermediates anywhere in a reaction mechanism is altered, all intermediates are affected

Reaction Mechanism•1) A + B <---> C + D

•2) C + D <---> E + K

•3) E + K <---> H + M

•4) H + M <----> P

Lab Results % 100 80 60 40

RT5.21 8.42 11.9 21.7

WR 2.75 4.23 7.96 11.2

Reaction

Quotient

where [A], [B], [P], and [Q] are molarities at any time.Q = K only at equilibrium.

aA(aq) + bB(aq) pP(aq) + qQ(aq)

Drill: NH3 H2 + N2

At a certain temperature at equilibrium Pammonia = 4.0 Atm, Phydrogen = 2.0 Atm, & Pnitrogen = 5.0 Atm.

Calculate Keq:

CHM II HW•Review PP 19 & 20

•Complete the attached assignment & turn it in tomorrow

Reaction

Quotient

where [A], [B], [P], and [Q] are molarities at any time.Q = K only at equilibrium.

aA(aq) + bB(aq) pP(aq) + qQ(aq)

•When K > Q, the reaction goes forward

•When K < Q, the reaction goes in reverse

Equilibrium Calculations•aA + bB pP + qQ

•Stoichiometry is used to calculate the theoretical yield in a one directional rxn

Equilibrium Calculations•aA + bB pP + qQ

•In equilibrium rxns, no reactant gets used up; so, calculations are different

Equilibrium Calculations•Set & balance rxn

•Assign amounts with x

•Write eq expression

•Substitute amounts

•Solve for x

Equilibrium Calculations•CO + H2O CO2 + H2

• Calculate the partial pressure of each portion at eq.when 100.0 kPa CO & 50.0 kPa H2O are combined:

•Kp = 3.4 x 10-2

Equilibrium Calculations CO H2O CO2 H2

100 -x 50 - x x x

PCO2PH2 x2

PCOPH2O (100-x) (50-x)

Kp = 3.4 x 10-2

Send to the next page

Equilibrium Calculations x2

(100 -x)(50 - x)

5000 -150x + x2

x2 = 170 - 5.1x + 0.034x2

0.966x2 + 5.1x - 170 = 0

= 3.4 x 10-2

Equilibrium Calculations0.966x2 + 5.1x - 170 = 0

Use the quadratic equation to solve for x

x = 11 x = -16Substitute 11 back into the

originally assigned #

Equilibrium Calculations CO H2O CO2 H2

100 -x 50 - x x x

100-11 50-11 11 11

PCO = 89 kPa PH2O = 39 kPa

PCO2 = 11 kPa PH2 = 11 kPa

Equilibrium CalculationsXe (g) + F2(g) XeF2(g)

Calculate the partial pressure of each portion when

50.0 kPa Xe & 100.0 kPa F2 are combined:

Kp = 4.0 x 10-1

Equilibrium Calculations Xe F2 XeF2

50 -x 100 - x x

PXeF2 x

PXePF2 (50-x) (100-x)

Kp = 4.0 x 10-1

Send to the next page

Equilibrium Calculations x(50 -x)(100 - x)

x5000 -150x + x2

x = 2000 - 60x + 0.40x2

0.40x2 -61x + 2000 = 0

= 4.0 x 10-1

Equilibrium Calculations0.40x2 - 61x + 2000 = 0

Use the quadratic equation to solve for x

x = 48 x = 105Substitute 48 back into the

original assignmented #

Equilibrium Calculations Xe F2 XeF2

50 -x 100 - x x

50-48 100-48 48

PXe = 2 kPa PF2 = 52 kPa

PXeF2 = 48 kPa

SO2 + O2 SO3

• Determine the magnitude of the equilibrium constant if the partial pressure of each gas is 0.667 Atm.

Drill: Write the equilibrium expression & solve its magnitude

when PNO2 & PN2O4

= 50 kPa each at eq:N2O4(g) NO2(g)

Review Drill&

Check HW

CHM II HW•Review PP-20•Complete the attached HW

CHM II Schedule:• Lab: Later this week

• Test Early next week

Equilibrium CalculationsXe (g) + 2 F2(g) XeF4(g)

Calculate the partial pressure of each portion when 75 kPa Xe & 20.0 kPa F2 are combined:

Kp = 4.0 x 10-8

Le Chatelier’s Principle

•If stress is applied to a system at equilibrium, the system will readjust to eliminate the stress

LC Eq Effects•A(aq) +2 B(aq) <--->

C(aq) + D(aq) + heat

•Write equilibrium exp:

•What happens if:

LC Eq Effects•2 A(aq) + B(s) <--->

C(aq) +2 D(aq) + heat

•Write equilibrium exp: What happens if:

LC Eq Effects•2 A(g) + 2 B(g) <--->

3 C(g) + 2 D(l)

•What happens if:

G = H - TSG = - RTlnKeq

Drill: Solve for K

A(aq)+ 2 B(aq) C(s)+ 2 D(aq)

Calculate Keq if:

[A] = 0.30 M [B] = 0.20 M

C = 5.0 g [D] = 0.30 M

Schedule•Lab: Friday

•Test: Next week

CHM II HW•Review PP-20

•Complete the attached assignment & turn it in tomorrow.

A(aq)+ B(aq) AB(aq)

Calculate the equilibrium concentration of each species

when equal volumes of

0.40 M A & 0.20 M B are combined.

Keq = 0.50

Equilibrium CalculationsXe (g) + F2(g) XeF2(g)

Calculate the partial pressure of each portion when 80.0 kPa Xe & 60.0 kPa F2 are combined:

Kp = 4.0 x 10-2

Drill: A + B C + D

Calculate the equilibrium concentration of each species

when equal volumes of

0.60 M A & 0.80 M B are combined.

Keq = 5.0 x 10-6

CHM II HW•Review PPs 19 & 20

•Review both for the Test on Monday.

The Test on Rxn Rates & Chemical Equilibria will be

on Monday

We will return to the lab when the

class has no more field trips.

Working with Equilibrium Constants

When adding Reactions:

Multiply Ks

A B K1

B C K2

A C K3

K3 = (K1)(K2)

Solve K for each:

A + B C + D

C + D P + Q

A + B P + Q

When doubling Reactions:

Square Ks

2 A 2 B K2

K2 = (K1)2

When a rxn is multiplied by any factor, that factor

becomes the exponent of K

1/3 A 1/3 B K2

K2 = (K1)1/3

When reversing Reactions

Take 1/Ks

A B K1

B A K2

K2 = 1/K1

Equilibrium CalculationsCuCl6

-4 (aq) + 2 NH3(aq) [Cu(NH3)2Cl4]-2

Calculate the molarity of each portion when 0.10 M CuCl6

-4 & 1.0 M NH3 are combined: Kformation = 0.060

Equilibrium CalculationsRn(g) + F2(g) RnF2(g)

Calculate the partial pressure of each portion when 25 kPa Rn & 75 kPa F2 are combined:

Kp = 4.0 x 10-2

Drill: A + B P + Q

Calculate the concentration of each portion at equilibrium when 100.0 mL 0.50 M A is added to 150 mL 0.50 M B:

Kc = 6.0 x 10-8

Review Drill&

Check HW

Next Test

•Monday

Reviewfor theTest

Rate LawaA + bB pP + qQ

k[A]a[B]bRate =

Equilibrium EquationaA + bB pP + qQ

[P]p[Q]q

[A]a[B]bKc =at equilibrium

Reaction QuotientaA + bB pP + qQ

[P]p[Q]q

[A]a[B]bQ =at the other conditions

The data on the next slidewas obtained in lab. Usethat data to solve for the order with respect to each reactant, the reaction order,the rate expression, k, & Ea.

Experimental Results• Exp # [A] [B] Rate

• 127 1.0 1.0 2.0 x 10-2

• 227 2.0 1.0 4.0 x 10-2

• 327 1.0 2.0 8.0 x 10-2

• 477 1.0 1.0 2.0

Reaction Mechanism• Step 1 A <--> B fast

• Step 2 2 B <--> 3C fast

• Step 3 C <--> 2D fast

• Step 4 D P slow

LC Eq Effects•2 A(aq) + B(s) <--->

C(aq) +2 D(aq) + heat

•Write equilibrium exp: What happens if:

LC Eq Effects•3 A(g) + B(g) <--->

2 C(g) + 2 D(l)

•Write equilibrium exp:

•What happens if:

SO + O2 SO3

Calculate the equilibrium pressures if SO at 80.0 kPa

is combined with O2 at 40.0 kPa. K = 2.00

Equilibrium CalculationsI2 + 2 S2O3

-2 S4O6-2

+ 2 I-

Calculate the equilibrium concentration of each portion when it’s 0.25 M I2 & 0.50 M

S2O3-2 at the start of the rxn.

Kc = 4.0 x 10-8

Clausius-Claperon Eq

Ea= R ln(T2)(T1) k2

(T2 – T1) k1

Hv= R ln(T2)(T1) P2

(T2 – T1) P1

H = R ln(T2)(T1) K2

(T2 – T1) K1

Go = -RTlnK

Experimental Results• Exp # [A] [B] [C] time

• 1 1.0 1.0 1.0 16• 2 2.0 1.0 1.0 2• 3 1.0 2.0 1.0 8• 4 1.0 1.0 2.0 4

Drill: 1 A + 1 B 1 Z + 1 Y

Calculate the concentration of each portion at equilibrium

when 1.0 L 0.50 M A is added to 1.5 L 0.50 M B:

Kc = 2.0 x 10-2

Drill:Calculate the heat of reaction when K =

2.5 x 10-6 at 27oC, &

K = 2.5 x 10-4 at 127oC.

Write the Eq Expression AB(aq) A(aq)+ B(aq)

Calculate [A], [B], & [AB] at equilibrium when [AB] = 0.60 M at the start

Keq = 6.0 x 10-5

Write the Eq Expression PQ(aq) P(aq)+ Q(aq)

Calculate [P], [Q], & [PQ] at equilibrium when [PQ] = 0.90 M at the start

Keq = 9.0 x 10-5

Write the Eq Expression AB(aq) A(aq)+ B(aq)

Calculate [A], [B], & [AB] at equilibrium when [AB] = 0.60 M at the start

Keq = 6.0 x 10-5

Experimental Results• Exp # [A] [B] [C] Rate

• 1 0.1 0.1 0.2 2• 2 0.1 0.3 0.2 18• 3 0.1 0.1 0.8 8• 4 0.2 0.1 0.2 64

A + B <---> C + D

C + H <---> M + N

N + T <---> P + Q

•What happens all intermediates if:

1A + 1B 1P + 1Q[Ai] = 0.20 M Calcu-[Bi] = 0.30 Mlate the[Pi] = 0.20 M eq con-[Qi] = 0.30 M centra-Kc = 0.020 tion of ea.

Drill:

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