3.2.5 - Transition Metals

Question 1

Transition metals

Answer 1

Elements in the d-block of the periodic table with a partially filled d-orbital. They lose electrons to form positive ions with the s-orbital electrons being removed first

Question 2

Physical properties of transition metals

Answer 2

Similar physical properties, atomic radius, high densities and high melting and boiling points

Question 3

Chemical properties of transition metals

Answer 3

Form complexes, form coloured ions, variable oxidation states, good catalysts

Question 4

Complexes

Answer 4

form from transition metals, consisting of a central metal ion or atom surrounded by ligands

Question 5

Ligands

Answer 5

Molecules or ions with a lone electron pair that is able to form a coordinate bond to the central metal ions by donating this electron pair.

Question 6

Common ligands

Answer 6

Cl-
H2O
NH3

Question 7

Coordination number

Answer 7

Equal to the number of coordinate bonds formed around the central metal ion

Question 8

Coordination number of silver complexes

Answer 8

2

Question 9

Common coordination number of platinum complexes

Answer 9

4

Question 10

Exchange between ligands NH3 and H2O

Answer 10

They can be exchanged without a change in coordination number via a ligand substitution reaction

Question 11

Equation for ligand substitution reaction between NH3 and H2O ligands

Answer 11

[Co(H2O)6]2+ + 6NH3 –> [Co(NH3)6]2+ + 6H2O

Question 12

Exchange between copper complexes and NH3 in excess

Answer 12

The substitution is incomplete and the complex formed has a combination of water and ammonia ligands

Question 13

Equation for reaction between [Cu(H2O)6]2+ and NH3

Answer 13

[Cu(H2O)6]2+ + 4NH3 –> [Cu(H2O)2(NH3)4]2+ + 4H2O

Question 14

colour of [Cu(H2O)2(NH3)4]2+

Answer 14

forms as a deep blue solution

Question 15

Exchange between copper complexes and Cl-

Answer 15

Cl- ligand is much larger than NH3 and H2O ligands meaning substitution with this ligand results in a change in coordination number for that complex

Question 16

Equation for reaction between [Cu(H2O)6]2+ and Cl-

Answer 16

[Cu(H2O)6]2+ + 4Cl- –> [CuCl4]2- + 6H2O

Question 17

Complexes with just Cl- ligands always have…

Answer 17

a coordination number of 4, producing a tetrahedral shaped complex

Question 18

Bidentate ligands

Answer 18

Able to form two coordinate bonds to the central metal ion as they have two lone electron pairs

Question 19

Common bidentate ligands

Answer 19

Ethanedioate ions, ethane-1,2-diamine

Question 20

Ethanedioate ions

Answer 20

a lone pair electron on two of the oxygen atoms

Question 21

Ethane-1,2-diamine

Answer 21

a lone electron pair on each of the nitrogen atoms

Question 22

Multidentate ligands

Answer 22

Able to form up to six coordinate bonds to the central metal ion as they have multiple lone electron pairs

Question 23

Most common multidentate ligand

Answer 23

EDTA (ethylenediaminetetraacetic acid)

Question 24

Equation for reaction between iron compound and EDTA

Answer 24

[Fe(H2O)6]3+ + EDTA4- –> [FeEDTA]-1 + 6H2O

Question 25

Another common multidentate ligand is...

Answer 25

Haem that consists of six coordinate bonds around a central Fe2+ ion and its shape & structure allow it to transport oxygen

Question 26

Carbon monoxide

Answer 26

toxic to humans as it replaces the oxygen in the haem complex thus preventing it from being transported around the body

Question 27

The chelate effect

Answer 27

more moles on the right is achieved by substituting unidentate ligands with bidentate or multidentate ligands

Question 28

Positive entropy change

Answer 28

favourable as it means a more stable complex is being formed, it is favourable to have more moles on the right than the left

Question 29

Enthalpy change

Answer 29

very small as bonds being formed are very similar to the bonds that were broken

Question 30

Octahedral complexes

Answer 30

transition metal complexes with H2O and NH3 ligands commonly for octahedral complexes, bond angle 90°

Question 31

Cis-trans isomerism

Answer 31

shown by octahedral complexes with different types of unidentate ligands where ligands of the same type can be opposite or next to each other

Question 32

trans isomer

Answer 32

has two of the same ligands opposite each other

Question 33

cis isomer

Answer 33

has two of the same ligands next to each other

Question 34

optical isomerism

Answer 34

shown by octahedral complexes with bidentate ligands where the two isomers are mirror images of each other

Question 35

tetrahedral complexes

Answer 35

Form when complexes for with larger ligands e.g. Cl-, bond angle 109.5°. Can show optical isomerism

Question 36

Square planar complexes

Answer 36

form in Platinum and Nickel complexes, 4 coordinate bonds, bond angle 90°

Question 37

Linear complexes

Answer 37

form in silver complexes, 2 coordinate bonds, bond angle 180°

Question 38

Cisplatin

Answer 38

cis isomer of square planar complex of platinum

Question 39

Uses of cisplatin

Answer 39

cancer therapy drug

Question 40

Observing colour of compounds

Answer 40

White light shines on a substance some wavelengths are absorbed but remaining are reflected & transmitted to the eye. These reflected wavelengths correspond to a specific colour which is observed

Question 41

Electrons in the d-orbital...

Answer 41

exist in a series of energy states, when given energy they move from the ground state to the excited state. ∆E corresponds to a wavelength and frequency of light

Question 42

Colorimetry

Answer 42

An analytical technique that uses the absorption of visible light to determine the concentration of coloured ions by measuring absorbance

Question 43

Calibration graph

Answer 43

Produced by measuring solutions of known concentrations which can then be used to calibrate the colorimeter on a graph of relative absorbance against concentration

Question 44

Oxidation state of Vanadium in VO_2+

Answer 44

+5

Question 45

Ion colour of VO_2+

Answer 45

yellow

Question 46

Oxidation state of Vanadium in VO^2+

Answer 46

+4

Question 47

Ion colour of VO^2+

Answer 47

blue

Question 48

Oxidation state of V3+

Answer 48

+3

Question 49

Ion colour of V3+

Answer 49

green

Question 50

Oxidation state of V2+

Answer 50

+2

Question 51

Ion colour of V2+

Answer 51

violet

Question 52

Conditions for ions to be reduced

Answer 52

acidic

Question 53

Equation of reduction of VO_2+

Answer 53

2VO_2+ + 2e- + 4H+ --> 2VO^2+ + 2H2O

Question 54

Conditions for ions to be oxidised

Answer 54

alkaline as they react with water to produce OH- ions

Question 55

Equation for oxidation of VO^2+

Answer 55

VO^2+ + H2O --> VO_2+ + 2H+ + e-

Question 56

[Ag(NH3)2]+ (Tollens Reagent) is reduced by...

Answer 56

aldehydes to form silver atoms

Question 57

Equation for reduction of Tollens Reagent

Answer 57

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

Question 58

Heterogeneous catalyst

Answer 58

catalysts that are in a different phase to the species in the reaction

Question 59

Variable oxidation states make transition metals...

Answer 59

Good catalysts, electrons are transferred to produce a reactive intermediate and speed up the reaction rate

Question 60

Homogeneous catalyst

Answer 60

catalysts are in the same phase to the species in the reaction

Question 61

Adsorption

Answer 61

A solid catalyst works adsorbed molecule onto an active site on the surface of the catalyst. These active sites increase the proximity of molecules and weaken covalent bonds in molecules

Question 62

Catalyst poisoning

Answer 62

Heterogeneous catalysts can be poisoned by impurities which block active sites and prevent adsorption

Question 63

Homogeneous catalysts work by...

Answer 63

combining with reactants to produce a reactive intermediate which changes reaction path, activation energy is lower