I- Transition Metals

Question 1

What are transition metals?

Answer 1

metals that contain an incomplete d subshell in atoms/ ions
* top row (Sn-Cu) x Zn (∵ atom + ion have 10 e-)

Question 2

Properties

Answer 2

1. form coloured ions
2. form complexes
3. exhibit variable oxidation states
4. show catalytic activity
   eg.
   - Ni- magarine prod
   - V2O5- making SO3 for H2SO4
   - Fe- Haber process –> NH3
   - Pt, Pd- catalytic converters

Question 3

Ligand

Answer 3

• particle w/ lone pair
• that form co-ordinate bond to metal

Question 4

Complex

Answer 4

• metal ion w/ ligands
• co-ordinately bonded to it

Question 5

Co-ordination no.

Answer 5

no. of coordinate bonds from ligands to metal ions

Question 6

Lewis base

Answer 6

lp donor

eg. ligands, H2O

Question 7

Lewis acid

Answer 7

lp acceptor

Question 8

Calculating overall charge of a complex

Answer 8

overall charge = charge on metal ion + sum of ligand charges

Question 9

Shapes of complexes w/ 4 & 6 co-ordinate bonds respectively

Answer 9

4- tetrahedral (most of the time)
6- octahedral

Question 10

What is a ligand w/ 1 co-ordinate bond called?

Answer 10

unidentate ligand

Question 11

What is a ligand w/ 2 co-ordinate bonds called?

Answer 11

bidentate ligand

Question 12

What is a ligand w/ several co-ordinate bonds called?

Answer 12

multidentate ligand

Question 13

What kind of complexes have a linear shape?

Answer 13

Ag+ complexes
eg. [Ag(NH3)2]+

Question 14

What kind of complexes have a tertrahedral shape?

Answer 14

those w/ large ligands- eg. Cl-
eg. [CuCl4]2-

Question 15

What kind of complexes have a square planar shape?

Answer 15

Pt2+ complexes
eg. [PtCl4]2-

Question 16

What kind of complexes have an octahedral shape?

Answer 16

• those w/ 6 coordinate bonds
• most common
• eg. [Cu(H2O)6]2+

Question 17

Ligands like CO: and CN:- bond permaently. Why is that a problem?

Answer 17

• strong bonds formed
• x respire if too many rbc bonded

Question 18

How does cisplatin work (briefly)?

Answer 18

• cancer drug
• binds to guanine in DNA
• stops replication

Question 19

Factors causing a colour change

Answer 19

Δ in:
1. metal ion
2. type of ligand attached
3. co-ordination no.
4. oxidation state of transition metal

Question 20

sizes of H2O and Cl- ligands

Answer 20

• Cl- > H2O
  –> Cl- replaces H2O
• co no. ↓
• eg. [Co(H2O)6]2+ –> [CoCl4]2-

Question 21

sizes of H2O and NH3 ligands

Answer 21

~

Question 22

What is a partial substitution?

Answer 22

• some but x all ligands replaced
• eg. [Cu(H2O)6]2+ + 4NH3 –> [Cu(H2O)2(NH3)4]2+ + H2O

Question 23

What does ‘en’ stand for in diagrams?

Answer 23

ethandioate ion

Question 24

What is the chelate effect?

Answer 24

• small ΔH in sub reactions
• ∵ ~/ same no. of bonds broken + formed
• big ↑ in entropy (large +ve ΔS)
• products = thermodynamically ↑ stable than reactants

Question 25

nm to m unit conversion

Answer 25

1 nm = 1 x 10^-9 m

Question 26

What are d-d transitions?

Answer 26

• energy (in form of UV/ visible light) absorbed
• excites e- from lower d to higher d orbitals

Question 27

Colour of species with no d electrons

Answer 27

• x colour
• ∵ x d e- to excite

Question 28

Colour of species with 3d10

Answer 28

• x colour
• x vacant orbitals for e- to be promted to

Question 29

Planck relation equation

Answer 29

E = hv = hc/ λ
- E = energy
- h = Planck constant (JHz/ Js)
- v = freq (Hz)
- c = speed of light (3 x 10^8 ms-1)
- λ = wavelength (m)

Question 30

How does UV/ visible spectroscopy work?

Answer 30

1. light passed thru complex
2. amount passing thru measured (–> freq it absorbed)

Question 31

Colorimetry

Answer 31

• ↑ conc ↑ absorbed
• ligand added to intensify colour of some ions (eg. bipyradine)
• strength of absorption of known conc measured –> graph
• conc of solution w/ unknown conc found by measuring absorption + using graph

Question 32

What is a common oxidising agent used in redox titrations?

Answer 32

potassium manganate (VII), KMnO4
- MnO4 - + 8H+ + 5e- –> Mn2+ + 4H2O

Question 33

State a suitable reagent used in a redox titration involving MnO4 -, to achieve acidic conditions.

Answer 33

dilute H2SO4
- x HCl – MnO4 - would oxidise Cl- –> Cl2
- x conc. H2SO4/ conc. HNO3 – oxidising agents themselves
- ==> affects vol of KMnO4 required
- x weak acids – x provide enough H+

Question 34

5 C2O4 2- + 2MnO4 - + 16H+ –> 10CO2 + 2Mn2+ + 8H2O
Suggest why this reaction is slow to start.

Answer 34

2 -ve ions repel

Question 35

In a reaction between Fe2+ and MnO4 -, what is done if Fe is not in the +2 oxidation state?

Answer 35

• if element Fe (0) –> reacted w/ H2SO4–> oxidised
• if Fe (+3) –> reacted w/ Zn –> reduced (remaining Zn must be removed to stop it reducing Fe3+ formed in titration back to Fe2+)