Summer 2001 Notes

June 13 June 15 June 18 June 20 July 2

Fall 2001 Lectures

9/289/2810/110/310/5 – 10/8

2+

[Co(H2O)6]2+

Hydrolysis by complex ions

+ H2O(l)

+ H3O+

+ H2O(l)

+ H3O+

acidConjugatebase

Fe(H2O)63+(aq) + H2O(l)

H3O+(aq) + Fe(H2O)5OH2+(aq)

Fe(H2O)63+(aq) + H2O(l)

H3O+(aq) + Fe(H2O)5OH2+(aq)

Ka =[H3O+][Fe(H2O)5OH2+]

[Fe(H2O)63+]

= 7.7 x 10-3

Fe(H2O)63+(aq) + H2O(l)

H3O+(aq) + Fe(H2O)5OH2+(aq)

Ka =[H3O+][Fe(H2O)5OH2+]

[Fe(H2O)63+]

= 7.7 x 10-3

pH of 0.10 M Fe(H2O)63+

pH of 0.10 M Fe(H2O)63+

[Fe(H2O)63+] [H3O+] [Fe(H2O)5OH2+]

Startchangeequil.

0.10 0 0

pH of 0.10 M Fe(H2O)63+

[Fe(H2O)63+] [H3O+] [Fe(H2O)5OH2+]

Startchangeequil.

0.10 0 0

-x +x +x

pH of 0.10 M Fe(H2O)63+

[Fe(H2O)63+] [H3O+] [Fe(H2O)5OH2+]

Startchangeequil.

0.10 0 0

-x +x +x0.10 - x x x

pH of 0.10 M Fe(H2O)63+

[Fe(H2O)63+] [H3O+] [Fe(H2O)5OH2+]

Startchangeequil.

0.10 0 0

-x +x +x0.10 - x x x

Ka =(x)(x)

(0.10 - x)= 7.7 x 10-3

Ka =(x)(x)

(0.10 - x)= 7.7 x 10-3

pH of 0.10 M Fe(H2O)63+

Ka =(x)(x)

(0.10 - x)= 7.7 x 10-3

pH of 0.10 M Fe(H2O)63+

x2 = (7.7 x 10-3)(0.10 - x)

Ka =(x)(x)

(0.10 - x)= 7.7 x 10-3

pH of 0.10 M Fe(H2O)63+

x2 = (7.7 x 10-3)(0.10 - x)

x2 + (7.7 x 10-3)x - 7.7 x 10-4 = 0

Ka =(x)(x)

(0.10 - x)= 7.7 x 10-3

pH of 0.10 M Fe(H2O)63+

x2 = (7.7 x 10-3)(0.10 - x)

x2 + (7.7 x 10-3)x - 7.7 x 10-4 = 0

x = 0.024

Ka =(x)(x)

(0.10 - x)= 7.7 x 10-3

pH of 0.10 M Fe(H2O)63+

x2 = (7.7 x 10-3)(0.10 - x)

x2 + (7.7 x 10-3)x - 7.7 x 10-4 = 0

x = 0.024 pH = 1.6

Symmetry

Symmetry

Molecular symmetry

BF3

Symmetry

Molecular symmetry

BF3 BFF

F

Symmetry

Molecular symmetry

BF3 BFF

F

BFF

F

Symmetry

Molecular symmetry

BF3

BFF

F

Rotate 120o around an axis through B tothe plane of the screen.

Symmetry

Molecular symmetry

BF3

Rotate 120o

BFF

F

BFF

F

Symmetry

BF3

Rotate 120o

BFF

F

BFF

F

Since the fluorines are all identical,

we cannot tell the two molecules apart.

=

Symmetry

BFF

F

BFF

F

Since the fluorines are all identical,

we cannot tell the two molecules apart.

=

Rotate 120o Rotate 120o

Symmetry

BFF

F

Since the fluorines are all identical,

we cannot tell the two molecules apart.

=

Rotate 120o Rotate 120o

BFF

F

BFF

F

=

Symmetry

BF3

Rotate 120o

BFF

F

BFF

F

=

This is a 3-fold axis of symmetry.

A third 120o rotation brings themolecule back to the starting position.

Symmetry

BF3

BFF

F

Rotate 180o around the B - F axis.

Symmetry

BF3

Rotate 180o around the B - F axis.

BFF

F

BFF

F

Symmetry

BF3

Rotate 180o around the B - F axis.

BFF

F

BFF

F=

A second 180o rotation gives theoriginal molecule.

Symmetry

BF3

Rotate 180o around the B - F axis.

BFF

F

BFF

F

This is a 2-fold symmetry axis

=

Symmetry

BF3

BFF

F

BF3 has 3 2-fold symmetry axes.

Symmetry

BF3

BFF

F

B

F

mirror

Symmetry

BF3

BFF

F

B

F

Mirror plane of symmetry

BFF

F

=

Symmetry

BF3

BFF

F

B

F

BF3 has 3 mirror planes of symmetryalong the B-F bonds.

BFF

F

=

There is a mirror plane in the plane ofthe molecule.

BFF

F

1 3-fold axis normal to plane3 2-fold axes along B - F bonds3 mirror planes along bonds1 mirror plane in molecular plane

2+

2+

4-fold rotation axis

2+

4-fold rotation axis = 4 90o operations toget back to original configuration.

2+

4-fold rotation axis = 4 90o operations toget back to original configuration.

The octahedralcomplex willhave 3 4-foldaxes.

2+

Mirror planes?

2+

Mirror planes?

Co

OO

O O

2+

Mirror planes?

Co

OO

O O

3 mirror planes with Co and 4 H2O’s.

2+

Mirror planes?

Co

OO

O O

2+

Mirror planes?

Co

OO

O O

2+

Any otherrotation axes?

2+

Any otherrotation axes?

2+

Any otherrotation axes?

Octahedral complexes have 3-fold axes.

2+

Any othersymmetry elements?

2+

Any othersymmetry elements?

Inversion center

2+

Any othersymmetry elements?

Inversion centerThe Co is the inversion center.

2+

Any othersymmetry elements?

Inversion center

The Co is the inversion center. At any pointwhere there is a ligand, there is a ligand thesame distance in the opposite direction.

Tetrahedron

Tetrahedron

PerchlorateClO4

-

Tetrahedron PerchlorateClO4

-

1

2

3

4

1

2

3

4 =

2-fold

Tetrahedron PerchlorateClO4

-

1

2

3

4

1

2

3

4 =

Mirror plane

Tetrahedron PerchlorateClO4

-

1

2

3

41

2

3

4 =

3-fold axis Cl-O3

Tetrahedron PerchlorateClO4

-

1

2

3

4

4 3-fold rotations

3 2-fold rotations

3 mirror planes

+ others

octahemioctahedron

octahemioctahedron

4-fold rotation axes

octahemioctahedron

4-fold rotation axes

This is not a 3-fold

octahemioctahedron

4-fold rotation axes

This is not a 3-fold

octahemioctahedron

4-fold rotation axes

This is not a 3-fold

octahemioctahedron

4-fold rotation axes

This is not a 3-fold

a b The points a and b arerelated.

octahemioctahedron

4-fold rotation axes

ab

The combination of 120o

rotation and a mirrorleads to a new symmetryelement

octahemioctahedron

4-fold rotation axes

a b

The combination of 120o

rotation and a mirrorleads to a new symmetryElement - S3

Symmetry elements to look for-

rotations

mirrors

inversions

Crystals and solid-state structure

Crystals and solid-state structure

octahedron

Crystals and solid-state structure

Crystals and solid-state structure

Tetrahedralcoordination

Crystals and solid-state structure

Tetrahedralcoordination

C - C = 1.544 Å

Å = ångström = 10-10 m

Å = ångström = 10-10 m

The ångström is a useful unit when

describing bonding distances.

Symmetry of a tetrahedron

Tetrahedrons and cubes have 3-fold

axes of symmetry

Graphite Crystal

Graphite Structure

Graphite Structure

Hexagonal bondarray leads tohexagonal crystal

Graphite Structure

Bonds - strong attraction

Graphite Structure

Bonds - strong attraction

van der Waal’s forces- weak attraction

Hard structure - bondsare 3-dimensional

Soft structure - bonds are in twodimensions

Hard structure - bondsare 3-dimensional

Soft structure - bonds are in twodimensions

van der Waal’s forceseasy to break

BuckyBall a fullerene

C60

Individual moleculeof carbon atoms

OFB page 79crystals.

BuckyBall a fullerene

C60

NaCl

NaCl

SiO2

SiO2