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)

All gases N2 + 3 H2 2 NH3

All gases N2 + 3 H2 2 NH3 exothermic

All gases N2 + 3 H2 2 NH3 exothermic cool

All gases N2 + 3 H2 2 NH3 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.

C O N E T R A I (time)

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 expressions as partial pressures in atmospheres.

Law of Mass Action 1. Gases enter equilibrium expressions as partial pressures in atmospheres. 2. Dissolved species enter as concentrations in mol L-1.

Law of Mass Action 1. Gases enter equilibrium expressions as partial pressures in atmospheres. 2. Dissolved species enter as concentrations in mol L-1. 3. Pure solids and liquids are represented by 1 at equilibrium , a dilute solvent is 1.

Law of Mass Action 1. Gases enter equilibrium expressions as partial pressures in atmospheres. 2. Dissolved species enter as concentrations in mol L-1. 3. Pure solids and liquids are represented by 1 at equilibrium , a dilute solvent is 1. 4. Partial pressures or concentrations of products appear in the numerator, reactants in the denominator. Each is raised to the power of 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

I2 H2O CCl4

I2 H2O and CCl4 are immiscible H2O CCl4

I2(H2O) I2(CCl4) H2O CCl4

I2(H2O) I2(CCl4) [I2]CCl4 K = [I2]H2O H2O CCl4

I2(H2O) I2(CCl4) [I2]CCl4 K = [I2]H2O H2O = 85 Partition coefficient CCl4

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 CH3COO- = conjugate base H2O accepts H+ = base

Conjugate acid-base pairs. CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO-(aq) CH3COOH donates H+ = acid CH3COO- = conjugate base H2O accepts H+ = base H3O+ = conjugate acid

Conjugate acid-base pairs. CH3COOH(aq) + H2O(l) acid1 base2 H3O+(aq) + CH3COO-(aq) acid2 base1 CH3COOH donates H+ = acid CH3COO- = conjugate base H2O accepts H+ = base H3O+ = conjugate acid

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 Conjugate base = OH- H2O + H+ H3O+ H2O accepts H+ = base Conjugate acid = H3O+

Conjugate acid-base pairs. H2O H2O H+ + OH- H2O donates H+ = acid Conjugate base = OH- H2O + H+ H3O+ H2O accepts H+ = base 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)

Hydrogen carbonate ion Amphoteric molecules Hydrogen carbonate ion HCO3-(aq) + H2O(l) H2CO3(aq) + OH-(aq) base1 acid2 acid1 base2

Hydrogen carbonate ion Amphoteric molecules Hydrogen carbonate ion HCO3-(aq) + H2O(l) H2CO3(aq) + OH-(aq) base1 acid2 acid1 base2 HCO3-(aq) + H2O(l) CO32-(aq) + H3O+(aq)

Hydrogen carbonate ion Amphoteric molecules Hydrogen carbonate ion HCO3-(aq) + H2O(l) H2CO3(aq) + OH-(aq) base1 acid2 acid1 base2 HCO3-(aq) + H2O(l) CO32-(aq) + H3O+(aq) acid1 base2 base1 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) [H3O+][OH-] KW = [H2O]2

The pH scale Water always has some H3O+ and OH- present. 2 H2O(l) H3O+(aq) + OH-(aq) [H3O+][OH-] [H3O+][OH-] KW = = [H2O]2

The pH scale Water always has some H3O+ and OH- present. 2 H2O(l) H3O+(aq) + OH-(aq) [H3O+][OH-] [H3O+][OH-] = 1.0 x10-14 KW = = [H2O]2 @ 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-] 1.0 x 10-14 [H3O+] = 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-] 1.0 x 10-14 [H3O+] = = 1.0 x 10-13 0.1

pH of a water solution of a strong base. KOH(aq) + H2O(l) K+(aq) + OH-(aq) + H2O(l) 1.0 x 10-14 [H3O+] = = 1.0 x 10-13 0.1 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) 1.0 x 10-14 [H3O+] = = 1.0 x 10-13 0.1 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-] [H3O+] = 10-2.85 10-2.85 = 1.4 x 10-03 [H3O+] = 1.4 x 10-03 M

[H3O+] = 1.4 x 10-03 M 1.0 x 10-14 [OH-] = = 1.4 x 10-03

[H3O+] = 1.4 x 10-03 M 1.0 x 10-14 7.1 x 10-12 [OH-] = = 1.4 x 10-03

Acids and bases of varying strengths.

Acids and bases of varying strengths. Strong acid = 100% ionization Strong acid = 100% donation of acidic proton.

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

HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq) [H3O+][Cl-] K = [HCl]

HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq) [H3O+][Cl-] large K = = [HCl]

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

Generic acid HA(aq) + H2O(l) H3O+(aq) + A-(aq) [H3O+][A-] = acidity constant = Ka [HA]

Generic acid HA(aq) + H2O(l) H3O+(aq) + A-(aq) [H3O+][A-] = acidity constant = Ka [HA] -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-] = Kb = basicity constant [B]

[HB+][OH-] = Kb = basicity constant [B] [H3O+][B] = acidity constant = Ka [HB+] [H3O+][OH-] = Kw

[HB+][OH-] = Kb = basicity constant [B] [H3O+][B] = acidity constant = Ka [HB+] Conjugate acid [H3O+][OH-] = Kw KbKa = Kw

[HB+][OH-] = Kb = basicity constant [B] [H3O+][B] = acidity constant = Ka [HB+] [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-