Section 4 - Transition Metals

Question 1

Define transition metal:

Answer 1

A metal that can form one or more stable ions with a partially filled sub-shell.

Question 2

Which period 4, d-block elements are not transition metals?

Answer 2

Scandium and Zinc

Question 3

What are the 3 physical properties of transition metals?

Answer 3

• high density
• high mpts and bpts
• similar ionic radii

Question 4

What is the oxidation state/colour of:

MnO₄^-

Answer 4

+7 - purple

Question 5

What is the oxidation state/colour of:

Cr₂O₇^2-

Answer 5

+6 - Orange

Question 6

What is the oxidation state/colour of:

VO₂⁺

Answer 6

+5 - Yellow

Question 7

What is the oxidation state/colour of:

VO²⁺

Answer 7

+4 - Blue

Question 8

What is the oxidation state/colour of:

V³⁺

Answer 8

+3 - Green

Question 9

What is the oxidation state/colour of:

Cr³⁺

Answer 9

+3 - Green/Violet

Question 10

What is the oxidation state/colour of:

Fe³⁺

Answer 10

+3 - Yellow

Question 11

What is the oxidation state/colour of:

V²⁺

Answer 11

+2 - Violet

Question 12

What is the oxidation state/colour of:

Mn²⁺

Answer 12

+2 - Pale Pink

Question 13

What is the oxidation state/colour of:

Fe²⁺

Answer 13

+2 - Pale Green

Question 14

What is the oxidation state/colour of:

Co²⁺

Answer 14

+2 - Pink

Question 15

What is the oxidation state/colour of:

Ni²⁺

Answer 15

+2 - Green

Question 16

What is the oxidation state/colour of:

Cu²⁺

Answer 16

+2 - Blue

Question 17

Define Complex Ion

Answer 17

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

Question 18

What is the coordination number?

Answer 18

The number of coordinate bonds formed with the central metal ion

Question 19

What are the usual coordination numbers?

Answer 19

6 for small ligands eg. water, ammonia

4 for large ligands eg. Cl^-

Question 20

What are the bond angles in a tetrahedral compex ion shape?

Answer 20

109.5

Question 21

How do you calculate the oxidation state of a metal ion?

Answer 21

total oxidation state - sum of oxidation states of ligands

Question 22

What are the bond angles in a square planar complex ion?

Answer 22

90

Question 23

What complex ion forms a linear shape with bond angle 180?

Answer 23

[Ag(NH₃)₂]⁺

Question 24

What is a monodentate ligand?

Answer 24

One which can form only one bond

Question 25

What is a multidentate ligand?

Answer 25

One which can form more than one bond

Question 26

What are the chemical properties of transition metals? (4)

Answer 26

• form complex ions
• form coloured ions
• good catalysts
• variable oxidation states

Question 27

What is Haem?

Answer 27

Fe²⁺ ions with multidentate ligands

Question 28

How does Haem transport oxygen?

Answer 28

Oxygen forms a co-ordinate bond to Fe(II) in haemoglobin , enabling oxygen to be transported in the blood.

Question 29

Why is CO toxic?

Answer 29

Carbon monoxide is toxic because it replaces oxygen co-ordinately bonded to Fe(II) in haemoglobin.

Question 30

What type of isomerism do some complex ions show?

Answer 30

Optical - when a complex metal ion has 3 bidentate ligands coordinately bonded to it

Question 31

In which case can complex ions show E-Z isomerism?

Answer 31

When octahedral/square planar complex ions have monodentate ligands of various types

Question 32

What is the chelate effect?

Answer 32

When bidentate and multidentate ligands replace monodentate ligands from complexes.

Question 33

How do transition metals display colour?

Answer 33

Colour arises when some of the wavelengths of visible light are absorbed when electrons jump to the higher energy level and the remaining wavelengths of light are transmitted or reflected.

Question 34

What colour will you see if the 3d sub shell is full or empty?

Answer 34

White/colourless

Question 35

What happens to d electrons when light is absorbed?

Answer 35

They move from a ground state to an excited state

Question 36

The energy difference between the ground state and the excited state of the d electrons is given by:

Answer 36

∆E = hν = hc/λ

Question 37

What can cause a change of colour?

Answer 37

Changes in oxidation state, co-ordination number and ligand alter ∆E and this leads to a change in colour.

Question 38

How can spectroscopy be used to find concentrations of transition metal ions?

Answer 38

The absorption of visible light is used in spectroscopy. A simple colorimeter can be used to determine the concentration of coloured ions in solution.

Question 39

Why are complex ions with multidentate ligands more stable than with monodentate ligands?

Answer 39

The number of particles in the solution increases so there is a greater entropy and therefore it is more stable.

Question 40

What is redox potential dependent on?

Answer 40

• ligands attached
• pH

Question 41

How do you reduce Vanadium ions?

Answer 41

Vanadium species in oxidation states IV, III and II are formed by the reduction of vanadate(V) ions by zinc in acidic solution.

Question 42

Give the equation for the redox titration of Fe²⁺ with MnO₄^-

Answer 42

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

Question 43

Give the equation for the redox titration of C₂O₄^2- with MnO₄^-

Answer 43

2MnO₄^- + 16H⁺ + 5C₂O₄^2- –> 2Mn²⁺ + 8H₂O + 10CO₂

Question 44

What is a heterogenous catalyst?

Answer 44

A heterogeneous catalyst is in a different phase from the reactants and the reaction occurs at active sites on the surface.

Question 45

What are support mediums used for?

Answer 45

They are used to increase the surface area of the catalyst while minimising cost - the cayalyst is coated onto it

Question 46

Give the equation for the Iron catalyst in the Haber Process

Answer 46

N₂ + 3H₂ ——Fe——–> 2NH₃

Question 47

Give the equation for the Vanadium Oxide catalyst in the Contact Process for making sulfuric acid

Answer 47

SO₂ + 1/2O₂ ——-V₂O₅ ——-> SO₃

Question 48

Give the equations for the Vanadium catalyst regenerating itself

Answer 48

V₂O₅ + SO₂ —> V₂O₄ + SO₃

V₂O₄ + 1/2O₂ —> V₂O₅

Question 49

How is the iron catalyst poisoned in the Haber Process>

Answer 49

The methane which provides the hydrogen contains impurities (sulfur compounds) which adsorb onto the iron, stopping the catalyst from working effectively.

Question 50

What is a homogenous catalyst?

Answer 50

Catalysts in the same state as the reactants.

Question 51

How do homogenous catalysts provide a more effective route?

Answer 51

They combine with the reactants to form an intermediate species. The Ea to form this and then to form the products is lower than to form the products directly.

Question 52

Why are variable oxidation states important in catalysts?

Answer 52

Transition mtals can transfer electrons to speed up reactions.

Question 53

Why does the reaction between iodide ions and peroxodisulfate ions require a catalyst?

Answer 53

They are both negatively charged so repel each other meaning its unlikely they’ll collide and react.

Question 54

Give the equation for the reaction of S₂O₈^2- and I^- with an iron (II) catalyst and explain why it works.

Answer 54

S₂O₈^2- + I^- –> I₂ + 2SO₄^2- Overall equation

S₂O₈^2- + 2Fe²⁺ —> 2Fe³⁺ + 2SO₄^2- Iron ions are oxidised

2Fe³⁺ + 2I^- —> I₂ + 2Fe²⁺ Iron ions oxidise iodine ions and catalyst is regenerated

Question 55

What is autocatalysis?

Answer 55

When a product catalyses a reaction

Question 56

Give the equations for the reaction of the reaction of C₂O₄^2- and MnO₄^- with a Mn²⁺ catalyst

Answer 56

2MnO₄^- + 16H⁺ + 5C₂O₄^2- —> 2Mn²⁺ + 8H₂O + 10CO₂ Overall equation

MnO₄^- + 4Mn²⁺ + 8H⁺ —> 5Mn³⁺ + 4H₂O

2Mn³⁺ + C₂O₄^2- —> 2Mn²⁺ + 2CO₂