driving reactions to completion
DESCRIPTION
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). - PowerPoint PPT PresentationTRANSCRIPT
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-
