Transiton Metals

Question 1

What are transition metals

Answer 1

They are metals that form at least one stable ion with partially filled d orbitals

Question 2

Why aren’t zinc and scandium considered transition metals

Answer 2

Scandium only forms 3+ions with no electrons in the d orbital

Zinc only forms 2+ ions with a full d block

So they don’t form partially field d blocks

Question 3

What are 4 properties of transition metals

Answer 3

Complex ion formation
Formation of coloured ions
Variable oxidation state
Catalytic activity

Question 4

What is a ligand

Answer 4

It’s a molecule that forms a co ordinate bond with a transition metal by donating pair of electrons

Question 5

What is a complex ion

Answer 5

It’s a central metal atom surrounded by ligands and forms dative covalent bonds

Question 6

What is the co ordination number

Answer 6

The number of co ordinate bonds to the central metal ion

Question 7

State the ligands that form 6 bonds around a metal ion

Answer 7

NH3

H2O

Question 8

State the ligands that form 4 bonds

Answer 8

CL

CN

Question 9

What is a monodente ligand

Answer 9

One that has only one atom with a lone pair of electrons which forms bonds with a transition metal ion

Question 10

What is a multidentate ligand

Answer 10

When it has more than one atom with a lone pair of electrons and it forms bonds with transition metal ions

Question 11

What is the chelate effect and why does it occur

Answer 11

That bi dentate and multidente ligands replace monodentate ligands from complexd as they increase entropy for the reaction

There are moles of products than reactants from2-7 this creates more disorder

Question 12

Give an example of bidente ligands

Answer 12

En

C2O4(2-)

Question 13

What are the 4 shapes that complex ions form and give examples

Answer 13

Octahedral
Square planer-cisplatin (Pt)(NH3)2 (CL)2

Tetrahedral-[CO(CL)4

Linear- NH3–Ag–NH3

Question 14

State how many coordinate bonds CN,H20,OH,NH3

Answer 14

6

Question 15

How many co ordinate bonds does CL

Answer 15

4

Question 16

State the types of isomerism that complex ions form

Answer 16

Optical isomerism

Cis-trans isomerism

Question 17

State what optical isomerism and how it’s shown in complex ions and how can they be distinguished

Answer 17

Two non imposable mirror images are formed they can be distinguished by passing plane polarised light through the mixture and the enantiomers rotate them in equal but opposite directions

Question 18

State the use of AG(NH3)

Answer 18

It’s used as tollens reagent

Question 19

Give the use of cisplatin and how it works

Answer 19

It’s an anti cancer drug it prevents the cancer cell from replicating

Question 20

What 3 factors affect colour changes in transition metals

Answer 20

Ligand
Co-ordination number
Oxidation state

Question 21

Why does s change in ligand or coordination number result in a change in colour

Answer 21

It alters the energy split between the d-orbitals which changes the energy difference so the frequency of light absorbed changes

Question 22

Why do transition metals have different colours

Answer 22

When light hits a transition metal it’s absorbed which causes electrons to rise to from ground state to an excited state

The light that isn’t absorbed is transmitted which give the substance colour

Question 23

Why do Sn and Zn not have colour

Answer 23

SN ion doesn’t have any d electrons left

While Zn and cu have full n d blocks do there’s no energy transfer

Question 24

In redox titration state what acid is used and why HCL and nitric acid can’t be used

Answer 24

Conc HCL can’t be used as the CL- ions will be oxidised to chlorine

Nitric acid can’t be used as it’s an oxidising agent which leads to a small volume of managanate being produced

So dilute H2SO4 is produced

Question 25

What is the difference between heterogenous catalyst and homogenous catalyst

Answer 25

Heterogenous is in a different phase than the reactants Homogenous is in the same phase as reactants

Question 26

Give a way to improve the effectiveness of a catalyst

Answer 26

Increase the surface area

Question 27

Give an example of a homogenous catalyst and state where it's used

Answer 27

Fe 2+ Reaction between I- and S2O8 2-

Question 28

Give the equation for the catalyses reaction between I- and S2O82-

Answer 28

S2O8(2-) +2Fe(2+) -> 2SO4(2-) +2Fe3+ Stage 2- 2I- +2Fe(3+) ->2Fe2+ +I2

Question 29

Why is the Uncatalysed reaction between iodide and persulphate ions slow

Answer 29

Because the reaction needs the collision between two negative ions and they repel meaning high activation energy

Question 30

Why do the individual stages in the catalysed mechanism result in lower activation energies

Answer 30

As it involves collision between positive and negative lonw

Question 31

What is autocataylsis and give an example

Answer 31

It's w where one of the products can catalyse the reaction Mn2+

Question 32

What is colorimetery and what is it used for

Answer 32

It's when a light source is passed through in order to measure the amount of light of a certain wavelength passes through a coloured solution It helps in finding the formula of a solution Calibrate using a colorimeter

Question 33

Describe how colorimetery works

Answer 33

The two solutions are mixed together one which contains the metal ions and one with the ligands in different proportions This happens until they are mixed at the same ratio as they are in the complex this is the max conc so it has the highest absorbance

Question 34

What is absorbance

Answer 34

Measure of how much light is absorbed by a solution. The higher the concentration the higher the absorbance

Question 35

Why is water added in colorimetery

Answer 35

To maintain the volume

Question 36

What is poisoning

Answer 36

When the catalyst is poisoned by impurities and reduces the efficiency

Question 37

Give an example of a heterogenous catalyst and it's is

Answer 37

V2O5 | It's used in the contact process

Question 38

Give the equation of V2O5 in the contact process

Answer 38

So2+V2O5->So3+V2O4 2V2O4+O2->2V2O5

Question 39

In autocatalysis why is the uncatalysed reaction slow Between 2Mn and C2O4 (2-)

Answer 39

Because the reaction collision is between two negative ions which repel to give high activation energy

Question 40

What is the colour change of manganate in a titration and why does this occur

Answer 40

It's goes from colourless-purple and this is because the manganate is in excess

Question 41

Give the ionic equation of the reaction between manganate and fe

Answer 41

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

Question 42

What properties of transition metals enable them to be catalysts

Answer 42

The fact that they have variable oxidation states

Question 43

State what happens in adsorption and why do bonds in the reactant break

Answer 43

The reactants will form bonds with atoms at the active site on the catalyst surface This causes the bonds in reactants to break as they are weakened

Question 44

What happens in desorption

Answer 44

New bonds form between reactants on the catalyst This in turn weakens bonds between product and catalyst and this causes the product it leave so it desorbes

Question 45

When transition metals form ions where do they lose electrons from

Answer 45

They lose from 4s before 3D