transition metals

Question 1

what is a transition element?

Answer 1

an element which forms a stable ion which has a partially filled d sub shell

Question 2

what is a d block element?

Answer 2

an element which has its electrons in its d sub shell

Question 3

which d block elements aren’t transition metals and why?

Answer 3

scandium - has no electrons in its d sub shell when it forms an ion
zinc - has a full d sub shell when it forms an ion

Question 4

out of the 4s and 3d sub shell, which one fills up first?

Answer 4

4s

Question 5

what is the electron configuration of a chromium ion?

Answer 5

[Ar] 4s1 3p5

Question 6

what is the electron configuration of copper?

Answer 6

[Ar} 4s1 3d10

Question 7

give some of the properties of transition elements?

Answer 7

forms coloured ions
acts as a catalyst
has variable oxidation states
can form complexes

Question 8

what’s a complex?

Answer 8

a molecule with a transition metal ion in the centre with ligands coordinately bonded to them

Question 9

what is a ligand?

Answer 9

an atom or a molecule that donates a pair of electrons to a central metal ion to form a coordinate bond

Question 10

what is the coordination number?

Answer 10

the number of coordinate bonds formed to a central metal ion

Question 11

what is a monodentate ligand?

Answer 11

atoms or molecules which only form one coordinate bond to the complex ion

Question 12

give some examples of monodentate ligands

Answer 12

Cl-, NH3, H2O, OH- and CN-

Question 13

what are bidentate ligands?

Answer 13

molecules which have two atoms which each have a lone pair of electrons which can each form a coordinate bond to a central metal ion

Question 14

give an example of a bidentate ligand

Answer 14

ethane-1,2-diamine - H2NCH2CH2NH2

C2O4^2-

Question 15

what are multidentate ligands?

Answer 15

ligands which can form more than one coordinate bond to a central metal ion because they have multiple atoms with lone pairs available to form coordinate bonds

Question 16

give an example of a multidentate ligand

Answer 16

EDTA

Question 17

how many coordinate bonds does EDTA form?

Answer 17

6

Question 18

what is a ligand substitution reaction?

Answer 18

a reaction where one ligand which is coordinately bonded to a central metal ion is replaced by another ligand

Question 19

when does a ligand substitution reaction with no change in coordination number occur?

Answer 19

when small and uncharged ligands are used

Question 20

what is haem?

Answer 20

an iron(II) complex with a multidentate ligand

Question 21

how does haemoglobin carry oxygen?

Answer 21

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

Question 22

why is carbon monoxide toxic?

Answer 22

replaces oxygen, co-ordinately bonded to Fe(II) in haemoglobin so oxygen can’t be carried

Question 23

what is the chelate effect?

Answer 23

when bidentate and multidentate ligands replace monodentate ligands in a complex

Question 24

what is the link between coordination number and the enthalpy change?

Answer 24

no change in coordination number = no enthalpy change

more coordinate bonds broken than made means an increase in enthalpy

Question 25

what determines the entropy change of a ligand substitution reaction?

Answer 25

the number of reacting particles and the number of product particles

Question 26

what is the shape of a complex with 6 coordinate bonds joined to it?

Answer 26

octahedral

Question 27

what is the bond angle in octahedral complexes?

Answer 27

90

Question 28

which octahedral complexes form E-Z isomers?

Answer 28

Those in the form of ML4A2 (all monodentate)

Question 29

which octahedral complexes can form optical isomers?

Answer 29

Those formed from bidentate ligands

Question 30

what is the bond angle in tetrahedral complexes?

Answer 30

109.5

Question 31

give some examples of tetrahedral complexes

Answer 31

[CuCl4}2- [CoCl4]2- [FeCl4]-

Question 32

what is cisplatin

Answer 32

an ant-cancer drug

Question 33

what kind of isomerism does cisplatin show?

Answer 33

E-Z isomerism

Question 34

in what form is cisplatin active?

Answer 34

the Z form

Question 35

how does cisplatin work?

Answer 35

forms bonds between the bases in DNA so it stops DNA replication in tumour cells and stops tumours from growing

Question 36

what is the bond angle in square planar complexes?

Answer 36

90

Question 37

what happens to the d sub shell when a complex is formed?

Answer 37

it's split into two different orbitals at two different energy levels

Question 38

how are transition metal complexes coloured?

Answer 38

when they're hit by light, light is absorbed and promotes electrons from ground state to excited state some light is absorbed colour arises when other wavelengths are transmitted

Question 39

what does the colour of a complex depend on?

Answer 39

shape of the complex ligands attached to it coordination number metal ions and different charges

Question 40

what formula can you use to calculate energy difference between orbitals?

Answer 40

delta E = hv = hc/v ``` h = Planck constant c = speed of light v = frequency Hz ```

Question 41

give an example of a linear compound

Answer 41

[Ag(NH3)2]+

Question 42

what is colorimetry?

Answer 42

the measurement of colour intensity using a colorimeter

Question 43

how does a colorimeter work?

Answer 43

light shone through a sample and absorbance calculated filter used to get a specific wavelength of light absorbance compared against a calibration curve

Question 44

when do you use a spectrophotometer?

Answer 44

when the compound is colourless so colorimetry can't be used as the compound doesnt absorb visible light but does absorb UV light

Question 45

how can vanadium be reduced?

Answer 45

by a reducing agent such as zinc in the presence of an acid

Question 46

describe the colour change as vanadium goes from +5 to +2

Answer 46

yellow ---> blue ---> green ---> violet

Question 47

what is tollen's reagent used for?

Answer 47

testing for the presence of aldehydes and ketones

Question 48

what is potassium manganate used for?

Answer 48

titrations - testing how many moles of acid and alkali there are

Question 49

what is a homogenous catalyst?

Answer 49

a catalyst which is in the same physical state as the reactants

Question 50

what is a heterogenous catalyst?

Answer 50

a catalyst which is in a different phase to the reactants

Question 51

explain how catalysts work

Answer 51

by chemisorption - reactants are adsorbed onto the active site on the surface of the catalyst - reactant bonds weakened - held in a more favourable shape - product molecules leave the catalyst's surface

Question 52

how can catalysts be poisoned?

Answer 52

a substrate binds irreversibly to the active site so they have a reduced efficiency

Question 53

what are the implications of catalyst poisoning?

Answer 53

have to be replaced which is expensive

Question 54

how can catalyst poisoning be reduced?

Answer 54

purify reactants before reacting them

Question 55

what is autocatalysis?

Answer 55

when the product in a reaction acts as a catalyst for the reaction

Question 56

why is the reaction of manganate ions and ethanedioate ions slow at first?

Answer 56

both negatively charged so they repel each other because of the high activation energy

Question 57

why does the rate of reaction increase as manganate and ethanedioate ions react?

Answer 57

because Mn^2+ is formed which catalyses the reaction

Question 58

why can manganese and iron act as catalysts?

Answer 58

they have variable oxidation states

Question 59

what is the test for 3+ ions?

Answer 59

adding sodium carbonate and seeing if there's effervescence

Question 60

why are 3+ ions more acidic?

Answer 60

higher charge draw electrons in more (away from H) H is a better leaving group complex therefore acts as an acid

Question 61

what colour is potassium mangante in acid?

Answer 61

colourless

Question 62

what colour is potasium manganate in alkali?

Answer 62

purple

Question 63

name an example of homogenous catalysis?

Answer 63

S2O8^2- and I-

Question 64

give an example of autocatalysis?

Answer 64

MnO4- and C2O4^2-

Question 65

why is the reaction of MnO4- and C2O4^2- slow at first?

Answer 65

ions repel each other high activation energy small amount of catalyst at first