2.2.5 transition metals

Question 1

State the two types of reactions that can occur when the aqueous ions react.

Answer 1

Hydrolysis and Ligand Substitution

Question 2

The majority of the reactions create metal hydroxide precipitates.
Using ‘M’ to represent the central metal ion, give the formula of a metal hydroxide for a M2+ ion and a M3+ ion.

Answer 2

M2+ give M(H2O)4 (OH)2

M3+ give M(H2O)3(OH)3

Question 3

colour of each of the main ions:
Fe2+, Cu2+, Fe3+ and Al3+?

Answer 3

Fe2+ Green
Cu2+ Blue
Fe3+ Brown
Al3+ White

Question 4

tollens reagent

Answer 4

[Ag(NH3)2}+

Question 5

What is the equation for ΔE and what does it show

Answer 5

ΔE=hv
- ΔE is the change in energy
- h is planck’s constant
- v is the frequency of light
This is the energy difference between the ground state and the excited state of the d electorn

Question 6

Why do transition metals change in colour?

Answer 6

• Change in oxidation state
• Change in coordination number
• Change in ligands
• Change in ΔE

Question 7

redox equations for MnO4^-, Fe^2+ and Cr2O7^2-

Answer 7

8H+ + MnO4- + 5e- > Mn^2+ +4H2O
Fe^2+ > Fe^3+ +e-
Cr2O7^- +14H+ +6e- > 2Cr^3+ +7H2O

Question 8

…
Incomplete

Examples of bidentate ligands

Answer 8

• C2O4^2- (ethanedioate ion)
• [Cr(en)3]^3+ (ethan-1,2-diamine)

Question 9

Why do H2O and NH3 not experience a change in coordination number but Cl^- does?

Answer 9

• H2O and NH3 are of similar size and charge so no chnage
• Cl^- ligands are larger than the uncharged ligans and so can involve a chnage in co-oridnation number

Question 10

Complex definition

Answer 10

A complex is a central metal atom or ion surrounded by
ligands.

Question 11

Ligand Definition

Answer 11

A ligand is a molecule or ion that forms a coordinate bond with a transition metal by donating a pair of electrons.

Question 12

The characteristic properties include:

Answer 12

• complex formation
• formation of coloured ions
• variable oxidation state
• catalytic activity