AQA Transition Metals

Lewis Acid

Electron pair acceptor

Lewis Base

Electron pair donor

Transition Metal

A metal that can form at least one stable ion with a partially filled d-shell of electrons

Ligand

A molecule/atom that can act as a Lewis base to form a coordinate bond with a transition metal

Catalyst

A transition metal that can influence the rate of reaction by providing an alternative pathway with a lower activation energy needed for a reaction.

Colour

All metals look different ________ in their various oxidation states

A central metal atom or ion surrounded by co-ordinately bonded ligands

Complex

Redox

The variable oxidation states allows the transition metals to undergo a specific type of reaction

Coordination Number

Number of coordinate bonds in a complex ion

Haem

A square planar ligand attached to a ferrous group

Globin

A complex protein molecule attached to a ferrous group from below

Oxygen

The molecule that can actively bind to haemoglobin, but can also detach itself easily in the right conditions

Multidentate

A type of ligand that can form many coordinate bonds with ions

Bidentate

A type of ligand that can form two coordinate bonds with ions

Ethanedioate

A bidentate ligand that can act as a bridge between different molecules

Monodentate

A type of ligand that can form one coordinate bond with ions

Chelate

A complex ion involving multidentate ligands

The Chelate Effect

When monodentate ligands are substituted with multidentate ligands, the number of entities increases, the greater the entropy. Reactions that result in an increase in entropy are more likely to occur.

Linear

Shape of a complex ion with a coordination number of 2

Square Planar

Shape of a complex ions with a coordination number of 4 with similar sized ligands

Tetrahedral

Shape of a complex ions with a coordination number of 4 with different sized ligands

Octahedral

Shape of a complex ion with a coordination number of 6

Green

Colour of the iron complex [Fe(H2O)6] 2+

Pale Violet/Yellow

Colour of the iron complex [Fe(H2O)6] 3+

Yellow/Green

Colour of the copper complex [CuCl4]2-. Formed with an excess of H+ then Cl-

Blue

Colour of the copper complex [Cu(H2O)6] 2+

Colourless

The colour of the complex [Al(H2O)6]3+

Blue

Colour of the precipitate [Cu(OH)2(H2O)4]. Formed with an excess of OH-/NH3

Green to Brown

Colour of the precipitate [Fe(OH)2(H2O)4]. Then the colour change from oxidation in air. Formed with an excess of OH-/NH3

Brown

Colour of the precipitate [Fe(OH)3(H2O)3]. Formed using OH-/ NH3/ CO3 2-

Blue-green

Colour of the precipitate CuCO3, formed using CO3 2-

Green

Colour of the precipitate FeCO3, formed from using CO3 2-

Deep blue

Colour of the complex [Cu(H2O)2(NH3)4]2+. Formed with excess ammonia

Colorimeter

A way we can detect the wavelength of a sample by shining light at a substance and absorbing any remaining light that has not been absorbed by the sample

Heterogeneous Catalyst

A catalyst that exists in a different phase to that of the reactants e.g. Haber process

Adsorb reactants onto active sites on their surface

How heterogenous catalysts work

Poisoning

Impurities bind to surface and block reactants

Poisoning in the haber process

Methane (which supplies the hydrogen) contains sulfur impurities which adsorb to iron, forming iron sulphide

Homogeneous Catalyst

A catalyst that exists in the same phase as the reactants, enthalpy profile has 2 "humps" (formation of intermediate and then product)

Efficiency

These could increase ________ of a catalyst:
- Increasing surface area
- Spreading catalyst onto an inert medium, to increase the surface to mass ratio

Iron

The catalyst involved in the Haber Process
N2 + 3H2 -> 2NH3
This is a heterogeneous catalyst

V2O5

The catalyst involved in the contact process
2SO2 + O2 -> 2SO3

V2O5 + SO2 -> V2O4 + SO3

The first step in the catalytic reaction between V2O5 and SO2

2V2O4 + O2 -> 2V2O5

The second step in the catalytic reaction between V2O5 and SO2

Fe2+

The catalyst involved in the formation of iodine
S2O8 2- + 2I- -> 2SO4 2- + I2

S2O8 2- + 2Fe2+ -> 2SO4 2- + 2Fe3+

The first step involved in the reaction between Fe2+ and S2O8 2- (peroxodisulfate ions)

2Fe3+ + 2I- -> 2Fe2+ + I2

The second step involved in the reaction between Fe2+ and S2O8 2-

Autocatalysis

When a product catalyses the reaction

MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O

Reduction of manganate ions

MnO4- + 8H+ + 5Fe2+ -> Mn2+ + 4H2O + 5Fe3+

Reaction between iron (II) ions and manganate (VII) in titrations

RCHO + 2[Ag(NH3)2]+ +3OH- -> RCOO- + 2Ag + 4NH3 + 2H2O

The reaction of Tollens reagent with an aldehyde

Yellow, +5

VO2 + (colour and oxidation state)

Blue, +4

VO 2+ (colour and oxidation state)

Green, +3

V 3+ (colour and oxidation state)

Violet, +2

V 2+ (colour and oxidation state)

Orange, +6

Cr2O7 2- (colour and oxidation state)

Violet, +3

Cr 3+ (colour and oxidation state)

Violet, +7

MnO4 - (colour and oxidation state)

Pink, +2

Mn 2+ (colour and oxidation state)

Yellow, +3

Fe 3+ (colour and oxidation state)

Green, +2

Fe 2+ (colour and oxidation state)

Pink, +2

Co 2+ (colour and oxidation state)

Dark green, +2

Ni 2+ (colour and oxidation state)

Straw coloured

The colour of the [Co(NH3)6] 2+ complex formed in a ligand substitution reaction