driving reactions to completion

Driving reactions to completion

Driving reactions to completion

Completion = 100% yield of product

Cl-(aq) + Ag+

(aq) AgCl(s)

Cl-(aq) + Ag+

(aq) AgCl(s)

AgCl precipitates from the

solution.

Cl-(aq) + Ag+

(aq) AgCl(s)

AgCl precipitates from the

solution.

As the AgCl precipitates,

product is removed from solution.

Cl-(aq) + Ag+

(aq) AgCl(s)

N2 + 3 H2 2 NH3

All gases

N2 + 3 H2 2 NH3

All gases

exothermic

N2 + 3 H2 2 NH3

All gases

exothermic cool

N2 + 3 H2 2 NH3

All gases

exothermic cool

N2 + 3 H2 2 NH3

Although a lower temperature

favors more NH3 formed, the

lower temperature also leads to

a very slow reaction.

N2 + 3 H2 2 NH3

An increase in pressure should favor product.

N2 + 3 H2 2 NH3

An increase in pressure should favor product.

N2 + 3 H2 2 NH3

Ultimate solution: react at high

Temperature to speed up reaction,

cool until NH3 becomes liquid.

Remove from reaction vessel and repeat.

(time)

CONCENTRATION

Heterogeneous equilibrium

Heterogeneous equilibrium

Involves at least two phases.

Heterogeneous equilibrium

Involves at least two phases.

What is the concentration of

a pure liquid or a pure solid?

Concentrations are not a valid

way to define a pure liquid

or solid.

Concentrations are not a valid

way to define a pure liquid

or solid.

Moles water

Liters solvent= ?

The concentration of a pure liquid

or solid is defined as 1.

Law of Mass Action

Law of Mass Action

1. Gases enter equilibrium expressionsas partial pressures in atmospheres.

Law of Mass Action

1. Gases enter equilibrium expressionsas partial pressures in atmospheres.

2. Dissolved species enter as concentrations in mol L-1.

Law of Mass Action1. Gases enter equilibrium expressionsas partial pressures in atmospheres.

2. Dissolved species enter as concentrations in mol L-1.

3. Pure solids and liquids are represented by 1at equilibrium , a dilute solvent is 1.

Law of Mass Action

1. Gases enter equilibrium expressionsas partial pressures in atmospheres.

2. Dissolved species enter as concentrations in mol L-1.

3. Pure solids and liquids are represented by 1at equilibrium , a dilute solvent is 1.

4. Partial pressures or concentrations ofproducts appear in the numerator, reactants inthe denominator. Each is raised to the powerof its coefficient.

The partition coefficient:

The partition coefficient:

Materials are soluble to different

degrees in different solvents.

The partition coefficient:

Materials are soluble to different

degrees in different solvents.

This allows for a method to separate that

material from others.

Solvent a

Solvent b

Compound x

Solvent a

Solvent b

Compound x

[x]a [x]b

[x]a [x]b

Partition coefficient =

K =[x]b

[x]a

CCl4

H2O

I2

CCl4

H2O

I2

H2O and

CCl4 are

immiscible

CCl4

H2O

I2(H2O) I2(CCl4)

CCl4

H2O

I2(H2O) I2(CCl4)

K =[I2]H2O

[I2]CCl4

CCl4

H2O

I2(H2O) I2(CCl4)

K =[I2]H2O

[I2]CCl4

= 85

Partitioncoefficient

Acids and Bases

Acids and Bases

Arrhenius Acids and Bases

Acids and Bases

Arrhenius Acids and Bases

Acid : increases H+ concentration in water.

Acids and Bases

Arrhenius Acids and Bases

Acid : increases H+ concentration in water.

Base : increases OH- concentration in water.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acid : substance that can donate H+.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acid : substance that can donate H+.

Base : substance that can accept H+.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acid : substance that can donate H+.

Base : substance that can accept H+.

Do not require aqueous solutions.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Conjugate acid-base pairs.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Conjugate acid-base pairs.

Conjugate base: subtract H+ from acid formula.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Conjugate acid-base pairs.

Conjugate base: subtract H+ from acid formula.

Conjugate acid: add H+ to the base formula.

Conjugate acid-base pairs.

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

Acetic acid is a monoprotic acid.

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

H3O+(aq) + CH3COO-

(aq)

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

H3O+(aq) + CH3COO-

(aq)

CH3COOH donates H+ = acid

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

H3O+(aq) + CH3COO-

(aq)

CH3COOH donates H+ = acid

H2O accepts H+ = base

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

H3O+(aq) + CH3COO-

(aq)

CH3COOH donates H+ = acid

H2O accepts H+ = base

CH3COO- = conjugate base

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

H3O+(aq) + CH3COO-

(aq)

CH3COOH donates H+ = acid

H2O accepts H+ = base

CH3COO- = conjugate base

H3O+ = conjugate acid

Conjugate acid-base pairs.

CH3COOH(aq) + H2O(l)

H3O+(aq) + CH3COO-

(aq)

CH3COOH donates H+ = acid

H2O accepts H+ = base

CH3COO- = conjugate base

H3O+ = conjugate acid

acid1

base1

base2

acid2

Conjugate acid-base pairs.

H2O

H2O H+ + OH-

Conjugate acid-base pairs.

H2O

H2O H+ + OH-

H2O donates H+ = acid

Conjugate acid-base pairs.

H2O

H2O H+ + OH-

H2O donates H+ = acid

H2O + H+ H3O+

Conjugate acid-base pairs.

H2O

H2O H+ + OH-

H2O donates H+ = acid

H2O + H+ H3O+

H2O accepts H+ = base

+

+

+

Conjugate acid-base pairs.

Conjugate base: subtract H+ from acid formula.

Conjugate acid: add H+ to the base formula.

Conjugate acid-base pairs.

H2O

H2O H+ + OH-

H2O donates H+ = acid

H2O + H+ H3O+

H2O accepts H+ = base

Conjugate base = OH-

Conjugate acid = H3O+

Conjugate acid-base pairs.

H2O

H2O H+ + OH-

H2O donates H+ = acid

H2O + H+ H3O+

H2O accepts H+ = base

Conjugate base = OH-

Conjugate acid = H3O+

H2O can be both conjugate acid and base.

Trimethyl amine is a weak base.

What is the conjugate acid?

Trimethyl amine is a weak base.

What is the conjugate acid?

(CH3)3N

Trimethyl amine is a weak base.

What is the conjugate acid?

(CH3)3N

Trimethyl amine is a weak base.

What is the conjugate acid?

[(CH3)3NH]+

Conjugate acid

NaCN dissolved in water gives

a basic solution. Why?

NaCN dissolved in water gives

a basic solution. Why?

NaCN(s) + H2O(l) Na+(aq) + CN-

(aq) + H2O(l)

NaCN dissolved in water gives

a basic solution. Why?

NaCN(s) + H2O(l) Na+(aq) + CN-

(aq) + H2O(l)

NaCN dissolved in water gives

a basic solution. Why?

NaCN(s) + H2O(l) Na+(aq) + CN-

(aq) + H2O(l)

+ H2O(l) HCN(aq) + OH-(aq)

Non-aqueous solutions

Non-aqueous solutions

NH3(l)

Non-aqueous solutions

HCl(NH ) + NH3(l) NH4+

(NH ) + Cl-(NH )

3 3 3

Non-aqueous solutions

HCl(NH ) + NH3(l) NH4+

(NH ) + Cl-(NH )

3 3 3

acid1 base2 acid2 base1

Non-aqueous solutions

HCl(NH ) + NH3(l) NH4+

(NH ) + Cl-(NH )

3 3 3

acid1 base2 acid2 base1

Ammonia is the solvent.

Amphoteric molecules

Amphoteric molecules

An amphoteric molecule or ion can be

either an acid or a base depending on

conditions.

Amphoteric molecules

An amphoteric molecule or ion can be

either an acid or a base depending on

conditions.

water

Amphoteric molecules

An amphoteric molecule or ion can be

either an acid or a base depending on

conditions.

water H3O+

Amphoteric molecules

An amphoteric molecule or ion can be

either an acid or a base depending on

conditions.

water H3O+ OH-

Amphoteric molecules

Hydrogen carbonate ion

Amphoteric molecules

Hydrogen carbonate ion

HCO3-

Amphoteric molecules

Hydrogen carbonate ion

HCO3-(aq)

+ H2O(l) H2CO3(aq) + OH-(aq)

Amphoteric molecules

Hydrogen carbonate ion

HCO3-(aq)

+ H2O(l) H2CO3(aq) + OH-(aq)

acid1base1 base2

acid2

Amphoteric molecules

Hydrogen carbonate ion

HCO3-(aq)

+ H2O(l) CO32-

(aq) + H3O+(aq)

HCO3-(aq)

+ H2O(l) H2CO3(aq) + OH-(aq)

acid1base1 base2

acid2

Amphoteric molecules

Hydrogen carbonate ion

HCO3-(aq)

+ H2O(l) CO32-

(aq) + H3O+(aq)

HCO3-(aq)

+ H2O(l) H2CO3(aq) + OH-(aq)

acid1

acid1

base1

base1

base2

base2

acid2

acid2

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acid : substance that can donate H+.

Base : substance that can accept H+.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acid : substance that can donate H+.

Dependant on strength of base present.

Base : substance that can accept H+.

Acids and Bases

Brønsted-Lowrey Acids and Bases

Acid : substance that can donate H+.

Dependant on strength of base present.

Base : substance that can accept H+.

Dependant on strength of acid present.

The pH scale

The pH scale

Water always has some H3O+ and

OH- present.

The pH scale

Water always has some H3O+ and

OH- present.

2 H2O(l) H3O+(aq) + OH-

(aq)

The pH scale

Water always has some H3O+ and

OH- present.

2 H2O(l) H3O+(aq) + OH-

(aq)

KW =[H3O+][OH-]

[H2O]2

The pH scale

Water always has some H3O+ and

OH- present.

2 H2O(l) H3O+(aq) + OH-

(aq)

KW =[H2O]2

= [H3O+][OH-][H3O+][OH-]

The pH scale

Water always has some H3O+ and

OH- present.

2 H2O(l) H3O+(aq) + OH-

(aq)

KW =[H2O]2

= [H3O+][OH-][H3O+][OH-]

= 1.0 x10-14

@ 25oC

KW = [H3O+][OH-] = 1.0 x10-14 @ 25oC

KW = [H3O+][OH-] = 1.0 x10-14 @ 25oC

If [H3O+] = [OH-] what are their

concentrations at 25oC?

KW = [H3O+][OH-] = 1.0 x10-14 @ 25oC

If [H3O+] = [OH-] what are their

concentrations at 25oC?

[X][X] = 1.0 x 10-14

KW = [H3O+][OH-] = 1.0 x10-14 @ 25oC

If [H3O+] = [OH-] what are their

concentrations at 25oC?

[X][X] = 1.0 x 10-14

X2 = 1.0 x 10-14

KW = [H3O+][OH-] = 1.0 x10-14 @ 25oC

If [H3O+] = [OH-] what are their

concentrations at 25oC?

[X][X] = 1.0 x 10-14

X2 = 1.0 x 10-14

X = 1.0 x 10-7

pH = -log10[H3O+]

pH = -log10[H3O+]

[H3O+] = 1.0 x 10-7

pH = -log10[H3O+]

[H3O+] = 1.0 x 10-7

-log10(1.0 x 10-7) =

pH = -log10[H3O+]

[H3O+] = 1.0 x 10-7

-log10(1.0 x 10-7) = -1 x -7 = 7

pH neutral water = 7

pH of a water solution of a

strong acid.

pH of a water solution of a

strong acid.

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

pH of a water solution of a

strong acid.

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

Assume HCl dissociates 100%.

pH of a water solution of a

strong acid.

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

Assume HCl dissociates 100%.

0.1 M HCl 0.1 M H3O+

pH of a water solution of a

strong acid.

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

Assume HCl dissociates 100%.

0.1 M HCl 0.1 M H3O+

[H3O+] = 1.0 x 10-1 M

pH of a water solution of a

strong acid.

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

Assume HCl dissociates 100%.

0.1 M HCl 0.1 M H3O+

[H3O+] = 1.0 x 10-1 M pH = 1

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

[KOH] = 0.1 M

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

[KOH] = 0.1 M

KW = 1.0 x 10-14 = [H3O+][OH-]

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

[KOH] = 0.1 M

KW = 1.0 x 10-14 = [H3O+][OH-]

[H3O+] =1.0 x 10-14

0.1

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

[KOH] = 0.1 M

KW = 1.0 x 10-14 = [H3O+][OH-]

[H3O+] =1.0 x 10-14

0.1= 1.0 x 10-13

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

[H3O+] =1.0 x 10-14

0.1= 1.0 x 10-13

pH = -log10 1.0 x 10-13 =

pH of a water solution of a

strong base.

KOH(aq) + H2O(l) K+(aq) + OH-

(aq) + H2O(l)

[H3O+] =1.0 x 10-14

0.1= 1.0 x 10-13

pH = -log10 1.0 x 10-13 = 13

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

(2x)(x) = 1.0 x 10-14

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

(2x)(x) = 1.0 x 10-14

2x2 = 1.0 x 10-14

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

(2x)(x) = 1.0 x 10-14

2x2 = 1.0 x 10-14

x2 = 0.5 x 10-14

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

x2 = 0.5 x 10-14 x = 7.07 x 10-08

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

x2 = 0.5 x 10-14 x = 7.07 x 10-08

2x = 1.414 x 10-07

Exercise page 330

Compute pH of aqueous solution

having [H3O+] = 2x[OH-].

KW = [H3O+][OH-] = 1.0 x 10-14

x2 = 0.5 x 10-14 x = 7.07 x 10-08

2x = 1.414 x 10-07 -log10 2x = 6.85

Calculating concentration from pH.

Calculating concentration from pH.

Example 8-4, page 330

pH = 2.85, calculate [H3O+] [OH-]

Calculating concentration from pH.

Example 8-4, page 330

pH = 2.85, calculate [H3O+] [OH-]

[H3O+] = 10-2.85

Calculating concentration from pH.

Example 8-4, page 330

pH = 2.85, calculate [H3O+] [OH-]

[H3O+] = 10-2.85

10-2.85 = 1.4 x 10-03

Calculating concentration from pH.

Example 8-4, page 330

pH = 2.85, calculate [H3O+] [OH-]

10-2.85 = 1.4 x 10-03

[H3O+] = 1.4 x 10-03 M

[H3O+] = 10-2.85

[H3O+] = 1.4 x 10-03 M

[OH-] = 1.0 x 10-14

1.4 x 10-03=

[H3O+] = 1.4 x 10-03 M

[OH-] = 1.0 x 10-14

1.4 x 10-03= 7.1 x 10-12

Acids and bases of varying strengths.

Acids and bases of varying strengths.

Strong acid = 100% ionization

Strong acid = 100% donation of acidicproton.

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

K =[H3O+][Cl-]

[HCl]

HCl(aq) + H2O(l) H3O+(aq) + Cl-

(aq)

K =[H3O+][Cl-]

[HCl]= large

HA(aq) + H2O(l) H3O+(aq) + A-

(aq)

Generic acid

HA(aq) + H2O(l) H3O+(aq) + A-

(aq)

Generic acid

[H3O+][A-]

[HA]= Ka

= acidity constant

HA(aq) + H2O(l) H3O+(aq) + A-

(aq)

Generic acid

[H3O+][A-]

[HA]= Ka

= acidity constant

-log10 Ka = pKa

Acid Ka pKa

HI 1011 -11

HCl 107 -7

H2SO4 102 -2

CH3COOH 1.8 x 10-5 4.74

Table page 332

Base strength

Base strength

Inversely related to strength of

conjugate acid.

Base strength

Inversely related to strength of

conjugate acid.

H2O(l) + B(aq) HB+(aq) + OH-

(aq)

conjugate acid

H2O(l) + B(aq) HB+(aq) + OH-

(aq)

[HB+][OH-]

[B]= Kb = basicity

constant

[HB+][OH-]

[B]= Kb = basicity

constant

[H3O+][B]

[HB+]= Ka

= acidity constant

[H3O+][OH-] = Kw

[HB+][OH-]

[B]= Kb = basicity

constant

[H3O+][B]

[HB+]= Ka

= acidity constant

[H3O+][OH-] = Kw

KbKa = Kw

Conjugate acid

[HB+][OH-]

[B]= Kb = basicity

constant

[H3O+][B]

[HB+]= Ka

= acidity constant

[H3O+][OH-] = Kw

KbKa = Kw

pKb + pKa = pKw

KbKa = Kw

pKb + pKa = pKw

Expressions can be used for any

conjugate acid-base pair in water.

Indicators :

Usually a weak organic acid that has a

color different from its conjugate base.

Indicators :

Usually a weak organic acid that has a

color different from its conjugate base.

HA + H2O H3O+ + A-