3.2.5 Transition Metals Flashcards by Lucy Scott

Explain the chelate effect

Bidentate and multidentate ligands replace monodentate ligands from complexes
Increase in number of species present so increase in entropy

How well did you know this?

Not at all

Perfectly

What causes colours of transition metals

Colour arises when some of the wavelengths of visible light are absorbed and the remaining wavelengths of light are transmitted or reflected.
d electrons move from the ground state to an excited state when light is absorbed.

How well did you know this?

Not at all

Perfectly

What causes change in colour of transition metal complexes

Change in oxidation state, co-ordination number and ligand alter change E

How well did you know this?

Not at all

Perfectly

What causes Vanadium species in oxidation states IV, III and II

Reduction of V ions by zinc in acidic solution

How well did you know this?

Not at all

Perfectly

What influences redox potential for a transition metal ion changing from high to lower oxidation state

pH and the ligand

How well did you know this?

Not at all

Perfectly

Heterogeneous catalyst

In different phase from the reactants and the reaction occurs at active sites on the surface

How well did you know this?

Not at all

Perfectly

Homogeneous catalyst

In the same phase as reactants. When catalyst and reactants are in the same phase, the reaction proceeds through an intermediate species

How well did you know this?

Not at all

Perfectly

The contact process reactions

SO2 + V2O5 —> SO3 + V2O4 (redox)
2V2O4 + O2 —> 2V2O5
Overall : 2SO2 + O2 <=> 2SO3
Each step has lower activation energy than one step reaction

How well did you know this?

Not at all

Perfectly

Catalyst in contact process

V2O5 acts as heterogeneous catalyst

How well did you know this?

Not at all

Perfectly

Catalyst in Haber process

Fe used as heterogeneous catalyst
Pea size lumps to increase surface area

How well did you know this?

Not at all

Perfectly

Heterogeneous catalyst negatives

Can be poisoned by impurities that block active sites

How well did you know this?

Not at all

Perfectly

How do Fe2+ ions catalyse the reaction between I− and S2O82–

S2O82- (aq) + 2I-(aq) → 2SO42-(aq) + I2(aq)
Aqueous iron(II) ions catalyse the reaction:
Step1: S2O82-(aq) + 2Fe2+(aq) → 2SO42-(aq) + 2Fe3+(aq)
Step2: 2Fe3+(aq) + 2I-(aq) → 2Fe2+(aq) + I2(aq)

How well did you know this?

Not at all

Perfectly

How do Mn2+ ions autocatalyse the reaction between C2O42– and MnO4–

2MnO4-(aq) + 16H+(aq) +5C2O42-(aq) → 2Mn2+(aq) + 10CO2(g) + 8H2O(l)
Step1: 4Mn2+(aq) + MnO4-(aq) + 8H+(aq) → 5Mn3+(aq) + 4H2O(l)
Step2: 2Mn3+(aq) + C2O42-(aq) → 2CO2 (g) + 2Mn2+(aq)

How well did you know this?

Not at all

Perfectly

State what is meant by the term bidentate ligand.

Two atoms or two points of attachment
Each donating a lone electron pair

How well did you know this?

Not at all

Perfectly

Define coordinate bond

A shared electron pair or a covalent bond
Both electrons from one atom

How well did you know this?

Not at all

Perfectly

Meaning of the term autocatalytic

Product of the reaction acts as a catalyst

How well did you know this?

Not at all

Perfectly

4 oxidation states of vanadium + ion colours

+5 (VO2^+) yellow
+4 (VO^2+) blue
+3 (V^3+) green
+2 (V^2+) violet

How well did you know this?

Not at all

Perfectly

Describe the characteristic properties of the elements titanium to copper + explain in terms of electronic structure

Variable oxidation states
Catalysts
Form complex ions
Form coloured compounds
Transition elements are d-block elements which form one or more stable ions with an incomplete d subshell

How well did you know this?

Not at all

Perfectly

Define ligand

a molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons

How well did you know this?

Not at all

Perfectly

Define co-ordinate bond

A covalent bond where both electrons come from the same atom

How well did you know this?

Not at all

Perfectly

Define co-ordination number

number of co-ordinate bonds to the central metal atom or ion

How well did you know this?

Not at all

Perfectly

Describe the origin of the colour of a transition metal complex ion

Colour arises when some of the wavelengths of visible light are absorbed and the remaining wavelengths of light are transmitted or reflected

How well did you know this?

Not at all

Perfectly

Describe how the concentration of iron(ii) ions in aqueous solution can be found

Titrating with either potassium manganate(VII) solution or potassium dichromate(VI) solution

How well did you know this?

Not at all

Perfectly

Describe how heterogeneous catalysts can be made more efficient

Make the particles as small as possible to increase surface area

How well did you know this?

Not at all

Perfectly

Explain how a homogeneous catalyst works

The catalyst forms an intermediate with the reactant with a lower activation energy. The intermediate often has a different oxidation state to the original transition metal. At the end of the reaction the original oxidation state will reoccur.

D-block elements not classed as transition metals

Scandium- only forms 3+ ion- no electrons in 3d sub shell Zinc- only forms 2+ ion- complete 3d sub shell

Define complex

central metal atom or ion surrounded by ligands

What complexes are formed when a solution of ammonium vanadate(V) (NH4VO3) is reduced by zinc metal in acid conditions

[VO2(H2O)4]^+ [VO(H2O)5]^2+ [V(H2O)6]^3+ [V(H2O)6]^2+

State the observations when Na2CO3(aq) is added to a solution containing [Al(H2O)6]3+(aq) ions

White ppt Bubbles/effervescence

What are some characteristic physical properties of transition metals

Metallic, good conductors of heat and electricity, hard, shiny, high melting + boiling, low reactivity

Uses of iron

Vehicle bodies, to reinforce concrete

Uses of titanium

Jet engine parts

Uses of copper

Water pipes

Give some examples of transition metals catalysts and the processes/reactions they catalyse

Iron- Haber process Vanadium (V) oxide - Contact process MnO2 - decomposition of H2O2

Which electrons do transition metals lose first when forming ions

Define the term multidente ligand

A ligand that forms 3 or more co-ordinate bonds to the central metal ion

How many co-ordinate bonds does EDTA^4- form

Shape of platin (cisplatin)

Square planar 4 ligands (breaks rule)

What conditions are needed for a complex ion to display optical isomerism

Usually octahedral molecules with 2 or more bidente ligands Mirror images are non-superimposable

What happens to Co^2+, Cu^2+, Fe^3+ coordination numbers when Cl^- ligands replace NH3/H2O ligands

Decrease from 4 to 6 as Cl^- much larger ligand

What is haem’s metal ion, coordination number and ligands

Molecule that makes up protein chains Fe^2+ central metal ion Coordination number 6 4 bonds are to a ring system called porphyrin 1 is to nitrogen of a glob in molecule 1 is to oxygen of O2 molecule

How does haemoglobin transport oxygen

O2 forms weak coordinate bond to the metal ion Transported around the body Bond breaks when haemoglobin reaches cells and oxygen is released

Why is CO toxic

Coordinately bonds to Fe^2+ and is a better ligand Stops O2 from bonding and being transported around body

What can you use to reduce Vanadium

Zinc

What does a colorimeter do

Measures the absorbance of a particular wavelength of light by a solution

Why can transition metals have variable oxidation states

Have partially filled d-orbitals so can lose 4s and 2d electrons

When oxidation state is high, how do transition metals exist

Covalently bond to other species After oxidation state of around 3

What colour is MnO4^-

Deep purple

What colour is Mn^2+

Pink

What colour is Cr2O7^2- and Cr^3+

Orange Green

What happens to aqua metal ions in acidic conditions and alkaline conditions

Reduced acid Oxidised alkaline

What metals are used in catalytic converted and which reactions do they catalyse

Pt, Rd, Pd 2CO + 2NO —> 2CO2 + N2 Alkane + oxygen —> H2O + CO2

How do heterogeneous catalysts work

Reactants adsorb to the catalyst’s surface at active sites Weakens bond within reactants + hold them close together on surface Once reaction has occurred, products desorb from active sites

What properties make a good catalyst

Can’t adsorb too strongly as products won’t desorb Can’t adsorb too weakly as reactant wouldn’t be held in place long enough and bonds wouldn’t be sufficiently weakened

How to increase efficiency of heterogeneous catalysts

Increase surface area Spread onto inert support medium like ceramic honeycomb or mesh

What is catalyst poisoning

Unwanted impurities adsorb to catalyst’s active sites and don’t desorb

How can catalyst be degraded other than impurities poisoning

Finely divided catalysts can be gradually lost from their support medium

How long does catalyst in Haber process last + what is it poisoned by

5 years Sulphur impurities

Why does the reaction between S2O8^2- ions and I^- ions have high activation energy

2 negative ions Repel each other

Conc of reactant against time graph for auto catalysed reaction shape

Initially show - not much catalyst formed Rate increases as catalysts made Slows down as reactants are used up

How can you monitor the concentration of MnO4^- ions

Colorimeter