Transition Metals

Question 1

Define a ligand

Answer 1

An ion or molecule with at least one lone pair of electrons ,that donates them to transition metal ion to form a coordinate bond then a complex

Question 2

What is chelate effect

Answer 2

Chelate complexes with multidentate ligands are favoured over monodentate ligands and displace smaller ligands

E.g EDTA displace ligands that form fewer coordinate bonds

There’s an increases in entropy

More stable ion formed

Question 3

What type of ion is produced when transition metal compound is dissolved in water

Answer 3

Aqua ion with 6 H20 Ligand formed
-octahedral shape

Question 4

Discuss the role of iron as a heterogeneous catalyst in the Haber process.

Answer 4

1a Heterogeneous means in a different phase/state from
reactants
1b Catalyst speeds up reaction and is left unchanged OR
lowers the activation energy for the reaction

2a Hydrogen and nitrogen/reactants adsorb onto the surface
2b Bonds weaken/reaction takes place
2c Products desorb
Stage 3
3a Large surface area (of iron) by using powder or small pellets
3b Catalyst poisoned / sulfur poisons or binds to the catalyst
3c Active sites blocked

Question 5

Why reaction is slow before catalyst added

Answer 5

• due to the reactants having the same charge so they repel
  -meaning activation energy is high

Question 6

Give two equations to show how the vanadium(V) oxide acts as a catalyst
in this contact process.

Answer 6

V2O5 + SO2 → V2O4 + SO3

V2O4 + O2 → V2O5

Question 7

Explain why complexes formed from transition metal ions are coloured.

Answer 7

absorb (some) wavelengths of (visible)
light
to promote/excite electrons in d-orbitals
remaining
wavelengths of (visible)
light reflected

Question 8

how do heterogenous catalyst work

Answer 8

-reactants adsorb on the surface at active site
-this weaken bonds in the reaction
-reaction takes place then products desorb

Question 9

what is catalyst poisoning

Answer 9

when unwanted impurites adsorb to the catalyst active site and do not desorb

this blocks the active site on catalysts.

often by sulfur

Question 10

Give two equations to show how Fe2+ ions catalyse this reactions S2O8 2- + 2 I–→ 2 SO4 2–(aq) + I2(aq)

Answer 10

Fe 2+ + S2O8 —-> 2Fe 3+ + 2 SO4 2-

Fe 2+ + 2I——> I2 + 2Fe 2+