Summer 2001 Notes June 13 June 15 June 18 June 20 July 2 Fall 2001 Lectures 9/28 10/1 10/3 10/5 – 10/8

2+ [Co(H 2 O) 6 ] 2+

Hydrolysis by complex ions

+ H 2 O (l) + H 3 O +

+ H 2 O (l) + H 3 O + acid Conjugate base

Fe(H 2 O) 6 3+ (aq) + H 2 O(l) H 3 O + (aq) + Fe(H 2 O) 5 OH 2+ (aq)

Fe(H 2 O) 6 3+ (aq) + H 2 O(l) H 3 O + (aq) + Fe(H 2 O) 5 OH 2+ (aq) K a = [H 3 O + ][Fe(H 2 O) 5 OH 2+ ] [Fe(H 2 O) 6 3+ ] = 7.7 x 10 -3

Fe(H 2 O) 6 3+ (aq) + H 2 O(l) H 3 O + (aq) + Fe(H 2 O) 5 OH 2+ (aq) K a = [H 3 O + ][Fe(H 2 O) 5 OH 2+ ] [Fe(H 2 O) 6 3+ ] = 7.7 x pH of 0.10 M Fe(H 2 O) 6 3+

[Fe(H 2 O) 6 3+ ][H 3 O + ] [Fe(H 2 O) 5 OH 2+ ] Start change equil  0 0

pH of 0.10 M Fe(H 2 O) 6 3+ [Fe(H 2 O) 6 3+ ][H 3 O + ] [Fe(H 2 O) 5 OH 2+ ] Start change equil  0 0 -x +x +x

pH of 0.10 M Fe(H 2 O) 6 3+ [Fe(H 2 O) 6 3+ ][H 3 O + ] [Fe(H 2 O) 5 OH 2+ ] Start change equil  0 0 -x +x +x x x x

pH of 0.10 M Fe(H 2 O) 6 3+ [Fe(H 2 O) 6 3+ ][H 3 O + ] [Fe(H 2 O) 5 OH 2+ ] Start change equil  0 0 -x +x +x x x x Ka =Ka = (x)(x) ( x) = 7.7 x 10 -3

Ka =Ka = (x)(x) ( x) = 7.7 x pH of 0.10 M Fe(H 2 O) 6 3+

Ka =Ka = (x)(x) ( x) = 7.7 x pH of 0.10 M Fe(H 2 O) 6 3+ x 2 = (7.7 x )( x)

Ka =Ka = (x)(x) ( x) = 7.7 x pH of 0.10 M Fe(H 2 O) 6 3+ x 2 = (7.7 x )( x) x 2 + (7.7 x )x x = 0

Ka =Ka = (x)(x) ( x) = 7.7 x pH of 0.10 M Fe(H 2 O) 6 3+ x 2 = (7.7 x )( x) x 2 + (7.7 x )x x = 0 x = 0.024

Ka =Ka = (x)(x) ( x) = 7.7 x pH of 0.10 M Fe(H 2 O) 6 3+ x 2 = (7.7 x )( x) x 2 + (7.7 x )x x = 0 x = pH = 1.6

Symmetry

Molecular symmetry BF 3

Symmetry Molecular symmetry BF 3 B FF F

Symmetry Molecular symmetry BF 3 B FF F B FF F

Symmetry Molecular symmetry BF 3 B FF F Rotate 120 o around an axis through B to the plane of the screen.

Symmetry Molecular symmetry BF 3 Rotate 120 o B FF F B FF F

Symmetry BF 3 Rotate 120 o B FF F B FF F Since the fluorines are all identical, we cannot tell the two molecules apart. =

Symmetry B FF F B FF F Since the fluorines are all identical, we cannot tell the two molecules apart. = Rotate 120 o

Symmetry B FF F Since the fluorines are all identical, we cannot tell the two molecules apart. = Rotate 120 o B FF F B FF F =

Symmetry BF 3 Rotate 120 o B FF F B FF F = This is a 3-fold axis of symmetry. A third 120 o rotation brings the molecule back to the starting position.

Symmetry BF 3 B FF F Rotate 180 o around the B - F axis.

Symmetry BF 3 Rotate 180 o around the B - F axis. B FF F B FF F

Symmetry BF 3 Rotate 180 o around the B - F axis. B FF F B FF F = A second 180 o rotation gives the original molecule.

Symmetry BF 3 Rotate 180 o around the B - F axis. B FF F B FF F This is a 2-fold symmetry axis =

Symmetry BF 3 B FF F BF 3 has 3 2-fold symmetry axes.

Symmetry BF 3 B FF F B F mirror

Symmetry BF 3 B FF F B F Mirror plane of symmetry B FF F =

Symmetry BF 3 B FF F B F BF 3 has 3 mirror planes of symmetry along the B-F bonds. B FF F =

There is a mirror plane in the plane of the molecule.

B FF F 1 3-fold axis normal to plane 3 2-fold axes along B - F bonds 3 mirror planes along bonds 1 mirror plane in molecular plane

2+

4-fold rotation axis

2+ 4-fold rotation axis = 4 90 o operations to get back to original configuration.

2+ 4-fold rotation axis = 4 90 o operations to get back to original configuration. The octahedral complex will have 3 4-fold axes.

2+ Mirror planes?

2+ Mirror planes? Co O O O O

2+ Mirror planes? Co O O O O 3 mirror planes with Co and 4 H 2 O’s.

2+ Mirror planes? Co O O O O

2+ Mirror planes? Co O O O O

2+ Any other rotation axes?

2+ Any other rotation axes?

2+ Any other rotation axes? Octahedral complexes have 3-fold axes.

2+ Any other symmetry elements?

2+ Any other symmetry elements? Inversion center

2+ Any other symmetry elements? Inversion center The Co is the inversion center.

2+ Any other symmetry elements? Inversion center The Co is the inversion center. At any point where there is a ligand, there is a ligand the same distance in the opposite direction.

Tetrahedron

Perchlorate ClO 4 -

Tetrahedron Perchlorate ClO = 2-fold

Tetrahedron Perchlorate ClO = Mirror plane

Tetrahedron Perchlorate ClO = 3-fold axis Cl-O3

Tetrahedron Perchlorate ClO fold rotations 3 2-fold rotations 3 mirror planes + others

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 are related.

octahemioctahedron 4-fold rotation axes a b The combination of 120 o rotation and a mirror leads to a new symmetry element

octahemioctahedron 4-fold rotation axes a b The combination of 120 o rotation and a mirror leads to a new symmetry Element - S 3

Symmetry elements to look for- rotations mirrors inversions

Crystals and solid-state structure

octahedron

Crystals and solid-state structure

Tetrahedral coordination

Crystals and solid-state structure Tetrahedral coordination C - C = Å

Å = ångström = 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

Hexagonal bond array leads to hexagonal crystal

Graphite Structure Bonds - strong attraction

Graphite Structure Bonds - strong attraction van der Waal’s forces- weak attraction

Hard structure - bonds are 3-dimensional Soft structure - bonds are in two dimensions

Hard structure - bonds are 3-dimensional Soft structure - bonds are in two dimensions van der Waal’s forces easy to break

BuckyBall a fullerene C 60 Individual molecule of carbon atoms OFB page 79 crystals.

BuckyBall a fullerene C 60

NaCl

SiO 2