Transitional Metals

Question 1

Characteristics of transition metals

Answer 1

Variable OS caused by the small energy difference between the 3d and 4s orbitals
Form coloured compounds due to d-d electron transitions
form complex ions - bc they have high charge density and available empty D orbitals

Question 2

define a Ligand, and co-ordination number

Answer 2

a ligand is an atom ion or molecule which forms a coordinate bond with a transition metal ion by donating an LP

Question 3

Bidentate and multidentate ligand

Answer 3

bidentate = 2 Lone pairs
Multidentate = more than 2 lone pairs

Question 4

commonly, what shape complex does a chloride ligand form

Answer 4

tetrahedral since Cl ion is large
(coordination number 4)

Question 5

which metals form square planar structures

Answer 5

Ni Pt Pd (2+)

Question 6

how the concentration of iron(ii) ions in aqueous
solution can be found?

Answer 6

redox titration since it very pale green for colourimetry
react with KMnO4 in titration
KmnO4 strong oxidising agent and coloured violet
Fe2+ —-> Fe3+ MnO4- —–> Mn2+
First permanent Pale pink shows KMnO4 in Excess
self-indicating process

Question 7

Homogeneous catalyst/ autocatalysis process

Answer 7

S2O8^2– + 2I– → I2 + 2SO4^2– (- overall)

S2O8^2– + 2Fe^2 + → 2Fe^3 + + 2SO4^2–
2Fe^3+ + 2I– → 2Fe^2 + + I2

Question 8

other autocatalysis ( vanadium in the contact process) ( production of sulfur trioxide)

Answer 8

2SO2 + O2 → 2SO3 (catalyst: V2O5) - Overall

V2O5 + SO2 → V2O4 + SO3
V2O4 + 1/2 O2 → V2O5

Question 9

Mn04- autocatalysis

Answer 9

2MnO4⁻ + 16H⁺ + 5C2O4²⁻ → 2Mn²⁺ + 8H2O + 10CO2

Intermediate Reactions:
4Mn²⁺ + MnO4⁻ + 8H⁺ → 5Mn³⁺ + 4H2O
2Mn³⁺ + C2O4²⁻ → 2CO2 + 2Mn²⁺

Question 10

how does a catalyst work

Answer 10

molecules adsorb onto the active site of the catalyst
they weaken the covalent bonds in the molecule
desorb

Question 11

explain, in terms of the charge/size ratio of the metal ion, why the acidity of [M(H2 O)6 ]3+ is greater than that of [M(H2 O)6 ]2+

Answer 11

M3+ higher charge density than m2+
so greater polarisation of OH bonds in water molecules
H+ lost more easily since OH bond weaker

Question 12

Explain the chelate effect in terms of the balance between entropy and enthalpy changes

Answer 12

The enthalpy change (ΔH) for ligand substitution is similar when replacing monodentate ligands with bi/multi dentate ligands.

However, the entropy change (ΔS) more positive when multidentate ligands used since more particles are produced (e.g., 2 monodentate ligands are replaced by 1 bidentate ligand → increase in disorder).

A more positive entropy change makes the Gibbs free energy change (ΔG = ΔH – TΔS) more negative, making the reaction more thermodynamically favorable.

Question 13

define a transition metal

Answer 13

a metal which can form ions with partially filled D orbitals