Transition Metals

Question 1

colour of V^(2+) (oxidation state 2)

Answer 1

purple

Question 2

colour of V^(3+) (oxidation state 3)

Answer 2

blue

Question 3

colour of VO^(2+) (oxidation state 4)

Answer 3

green

Question 4

colour of VO2^(+) (oxidation state 5)

Answer 4

yellow

Question 5

[Cu(H2O)6]^(2+) +2OH-/2NH3 —–>

products, type of reaction and colour change

Answer 5

[Cu(H2O)4(OH)2] + 2H2O/2NH4+
acid base reaction
pale blue sol——> blue ppt

Question 6

[Cu(H2O)4(OH)2] + 4NH3(conc)———>

products, type of reaction and colour change

Answer 6

[Cu(NH3)4(H2O)2]^(2+) +2OH- and 2H2O
ligand substitution
blue ppt——-> deep blue solution

Question 7

[Cu(H2O)6]^(2+) + 4Cl- ———–>

(products, type of reaction and colour change)

Answer 7

[CuCl4]^(2-) + 6H2O
coordination no. change
blue sol——> yellow sol (when there a mixture of the two it is green sol

Question 8

Fe(H2O)6 + 2OH-/NH3——->

Answer 8

[Fe(H2O)4(OH-)2] + 2h2O/2nh4+

green sol—–> green ppt

Question 9

[Fe(H2O)4(OH)2] when left in air —>

Answer 9

[Fe(H2O)3(OH)3]

green ppt—-> brown ppt

Question 10

Co(H2O)6 +2OH-/2NH3—->

Answer 10

[Co(H2O)4(OH)2] +2H2O/2NH4-

pink sol—-> blue ppt

Question 11

[Co(H2O)4(OH)2] + conc 6NH3—->

Answer 11

[Co(NH3)6]2+

blue ppt—–> yellow/light brown solution

Question 12

[Co(NH3)6]2+ left in air——->

Answer 12

[Co(NH3)6]3+ (It oxidises in air)

yellow/brown solution—–> brown sol

Question 13

[Co(OH)2(H2O)4] when left in air—>

Answer 13

[Co(OH)3(H2O)3]

blue ppt——>brown ppt

Question 14

[Cr(h2o)6]^(3+) + 3OH-/3NH3——->

Answer 14

Cr(OH)3(H2O)3

violet sol—-> green ppt

Question 15

Cr(OH)3(H2O)3 + 3NH3 (conc) ——>

Answer 15

{Cr(NH3)6]^3+

green ppt—–>violet sol

Question 16

Cr(OH)3(H2O)3 +3OH- (conc)—->

Answer 16

[Cr(OH)6]^3-

green ppt—–> green sol

Question 17

[Cr(OH)6] ^3- + H2o2 in alkaline conditions—->

Answer 17

CrO4 ^(2-)

green sol—–yellow sol

Question 18

CrO4 ^(2-) + H+——>

Answer 18

Cr2O7^(2-)

yellow sol—–>orange sol

Question 19

Ionic equations for production of Fe3+ catalyst

Answer 19

S2O8(2-) + Fe(2+)—-> 2S2O4 + Fe3+

Fe3+ + 2I(-) ——> Fe2+ + I2

Question 20

Describe the mechanism of catalysis

Answer 20

1. Adsorption- reactants stock to surface of catalyst
2. Reaction- bonds of the reactants are weakened
3. desorption- products come off the surface of the catalyst

Question 21

Reactions of catalyst of the Contact Proces

Answer 21

V2O5 + SO2—> V2O4 + SO3

V2O4 + 0.5O2 ——> V2O5

Question 22

Define heterogenous catalysts

Answer 22

When the catalyst is in a different phase to the reactants

Question 23

Why are Zn and Sc not a transition metals?

Answer 23

Zn can only form a +2 ion and Sc3+. In these ions they have a completed orbital and so does not meet the criteria of having an incomplete d orbital in one of its compounds.

Question 24

define ‘complex’

Answer 24

central atom surrounded by ligands

Question 25

define 'ligand'

Answer 25

a species which can donate a lone pair of electrons

Question 26

how do coloured metal ions form?

Answer 26

Colour arises from electronic transitions from the ground state to excited states: between different d orbitals A portion of visible light of specific frequencies is absorbed to promote d electrons to higher energy levels. The light that is not absorbed is transmitted to give the substance colour.

Question 27

where do colour changes arise from

Answer 27

1. oxidation state 2. coordination number 3. ligand

Question 28

define 'unidentate ligands'

Answer 28

have one atom which can donate one lone pair of electrons- forms one coordinate bond

Question 29

define 'bidentate ligands'

Answer 29

have two atoms which can each donate one lone pair electrons- form two coordinate bonds

Question 30

define 'multidentate ligands'

Answer 30

can form several coordinate bonds

Question 31

examples of bidentate ligands

Answer 31

1,2-diaminoethane (en) | ethanedioate ligand C2O4^2-

Question 32

example of multidentate ligands

Answer 32

EDTA^4-

Question 33

shape of [CuCl4]^2- and why

Answer 33

tetrahedral | Cl- ligands are too large for more than 4 to fit around

Question 34

Cr2O7 + Zn in acidic conditions------>

Answer 34

[Cr(H2O)6]3+ | orange to green

Question 35

catalysed reaction between iodide and persulfate ions

Answer 35

stage 1 S2O82- + 2Fe2——-> 2SO42- + 2Fe3+ | stage2 2I- + 2Fe3+-------> 2Fe2+ + I2

Question 36

autocatalytic reaction between ethanedioate and manganate ions

Answer 36

Step 1: 4Mn(2+) + MnO4- + 8 H+--------->5Mn (3+) + 4 H2O | Step 2: 2Mn(3+) + C2O4(2-) -------->2Mn (2+ )+ 2CO2

Question 37

what is autocatalysis?

Answer 37

when a product of a reactions acts as a reagent

Question 38

Features of transition metals

Answer 38

shows variable oxidation states | can form complex ions

Question 39

why might one ion have a different colour to another ion?

Answer 39

different ligands would split the d orbitals to different extents so different frequencies of light are absorbed

Question 40

Why does Cr has a unexpected electron configuration?

Answer 40

Half filled d orbital are more stable | Paired electrons easily removed due to repulsion

Question 41

why is cisplatin an effective cancer treatment?

Answer 41

The Cl- ligands are on the left side of the complex, these can both be displaced and bind to DNA preventing the cell division of cancerous cells

Question 42

Why can transition metals form variable oxidation states

Answer 42

This is because the ions contain partially filled sub-shells of d electrons that can easily lose or gain electrons. The energy differences between the oxidation states are small

Question 43

what makes something a good homogenous catalyst

Answer 43

needs to have its electrode potential in between the two half equations so it can oxidise one reagent and reduce the other

Question 44

why is a solid catalyst a good thing?

Answer 44

it can be filtered off