ch 6 chemical equilibrium 4.0

Aqueous Solution Chemistry• Review of Chem. I and Chem II

Memorize lists of strong acids-bases

Simple definitionacid – donates a protonbase – accepts a proton

Also know what Lewis acids/bases are,

Memorize

Hydroxides of the alkalineearth metals also consideredto be strong bases

Also note:

Very, very important

Acids/Bases

Conjugate Acids and Bases

HAc + H2O = Ac- + H3O+

Acid Base C. Base C. Acid

NH3 + H2O = NH4+ + OH-

Base Acid C. Acid C. Base

Useful advice: They differ by one and only one proton

Is the acetate ion an acid or base?

Is methylamine an acid or base?

Useful advice: Acids have a proton to lose, bases don’t

Polyprotic acids/bases

Clicker questions

What is the conjugate acid for F-

a. F-2

b. Fc. HFd. H2F

What is the conjugate base for H2PO4-

a. HPO42-

b. H3PO4

c. PO43-

Is H2PO4- an acid or a base

a. Acidb. Basec. Depends

Acids/Bases

Amphiprotic Species– behave as both an acid and a base– ex. H2O is an amphiprotic solvent– ex. H2PO4

-

H2PO4- + H2O = H3PO4 + OH-

H2PO4- + H2O = HPO4

2- + H3O+

Useful advice: the pH of an aqueous solution of anamphiprotic salt is determined by its equilibrium constants

Chemical EquilibriumReaction:

aA + bB = cC + dD

Chemical EquilibriumReaction:

aA + bB = cC + dDK = [C]c [D]d / [A]a [B]b Memorize

Chemical EquilibriumReaction:

aA + bB = cC + dDK = [C]c [D]d / [A]a [B]b

Understood, [C] = [C]/[C]std

solutes: std state = 1 Mgases: std state = 1 barsolids. liq = pure solid, pure liquid

Memorize

Chemical EquilibriumReaction:

aA + bB = cC + dDK = [C]c [D]d / [A]a [B]b

Understood,[C] = [C]/[C]std

solutes: std state = 1 Mgases: std state = 1 barsolids. liq = pure solid, pure liquid

• Make sure all concentrations in M

all gases in bar (atm)pure solids/liquids/solvents are omitted

Types of Equilibrium Constants

A. ion product constant for water2H2O = H3O+ + OH-

Types of Equilibrium Constants

A. Ion product constant for water2H2O = H3O+ + OH-

Kw = [H3O+] [OH-] = 1.00 x 10-14

pKw = -log Kw

Memorize

Types of Equilibrium Constants

A. ion product constant for water2H2O = H3O+ + OH-

K = [H3O+] [OH-] / [H2O]2

Kw = [H3O+] [OH-] = 1.00 x 10-14

pKw = -log Kw

B. solubility product constantAg2CO3(s) = 2Ag+ + CO3

-2

(temp dependent)

Types of Equilibrium Constants

A. ion product constant for water2H2O = H3O+ + OH-

K = [H3O+] [OH-] / [H2O]2

Kw = [H3O+] [OH-] = 1.00 x 10-14

pKw = -log Kw

B. solubility product constantAg2CO3(s) = 2Ag+ + CO3

-2

Ksp = [Ag+]2 [CO3-2] = 8.1 x 10-12

pKsp = -log Ksp

Types of Equilibrium Constants

C. Acid Dissociation Constant (Weak Acid)HNO2 + H2O = H3O+ + NO2

-

Types of Equilibrium Constants

C. Acid Dissociation Constant (Weak Acid)HNO2 + H2O = H3O+ + NO2

-

Ka = [H3O+ ] [NO2-] / [HNO2 ]

pKa = -log Ka

Types of Equilibrium Constants

C. Acid Dissociation Constant (Weak Acid)HNO2 + H2O = H3O+ + NO2

-

Ka = [H3O+ ] [NO2-] / [HNO2 ]

pKa = -log Ka

D. Base Dissociation Constant (Weak Base)NH3 + H2O = OH- + NH4

+

Kb = [OH- ] [NH4+] / [NH3 ]

pKb = -log Kb

Types of Equilibrium Constants

E. Relationship btwn Ka and Kb conjugate acid base pairs

ex. NH3 and NH4+

NH3 + H2O = OH- + NH4+ Kb = [OH- ] [NH4

+] / [NH3 ]

NH4+ + H2O = H3O+ + NH3 Ka = [H3O+ ] [NH3 ] / [NH4

+ ]

KaKb = Kw Memorize

Useful advice: “a” is for acid, “b” is for base…

Clicker Question:

Which one of the following weak acids will bestronger in water?

a. Acetic acid Ka = 1.75 x 10-5 b. Benzoic acid Ka = 6.28 x 10-5

c. HF Ka = 6.8 x 10-4

d. HCN Ka = 6.2 x 10-10

Types of Equilibrium Constants

F. Le Chatelier’s PrincipleSystem will change to relieve the stress

Ex. Ag2CO3(s) = 2Ag+ + CO3-2

Ksp = [Ag+]2 [CO3-2] = 8.1 x 10-12

Disturb the system (Add CO3-2)

Clicker question

A. Shift right (form more products)B. Shift left (form more reactants)

“Common ion effect”

Types of Equilibrium Constants

F. Le Chatelier’s PrincipleSystem will change to relieve the stress

Ex. Ag+ + 2NH3 = Ag(NH3)2+ 2 = K1K2

Disturb the system (Add NH3)

Can also set up the reaction quotient, Q

How many grams of barium iodate can be dissolved in 500.0 mL of water at 25 C?

What is the molar solubility of Ag2CO3 in 0.1 M AgNO3

Example Solubility Problems