transition metals

Question 1

give 4 properties of transition metals

Answer 1

they form complexes
they form coloured ions
variable oxidation states
good catalysts

Question 2

give 3 common ligands

Answer 2

Cl-
H2O
NH3

Question 3

why does a coordination number not change with a substitution of NH3 for H2O

Answer 3

the ligands NH3 and H2O are similar size and are both uncharged

Question 4

Give Eq of a ligand substitution reaction of Hexaaquacobalt2 + ammonia

Answer 4

[Co(H2O)6]2+ + 6NH3 ———> [Co(NH3)6]2+ + 6H20

Question 5

give Eq of Hexaaquacopper2 + excess ammonia

Answer 5

[Cu(H2O)6]2+ + 4NH3 ———> [Cu(H2O)2(NH3)4]2+ + 4H2O

Question 6

Why does coordination number change with Cl- ligand substitution

Answer 6

Cl- is much larger

Question 7

give Eq for Hexaaquacopper2+ + chloride ions

Answer 7

[Cu(H2O)6]2+ +4Cl- ————> [CuCl4]2- +6H2O

Question 8

what shape and coordination number do complexes with just Cl- ligands have

Answer 8

4
tetrahedral

Question 9

2 Bidentate ligands examples
where are lone pairs

Answer 9

Ethanedioate (C2O4)2-
lone pair on each of the single bonded oxygen atoms

Ethane-1,2-diamine (NH2(CH2)2NH2) lone pairs on each of the Nitrogens

Question 10

what is coordination number when a bidentate ligands substitute for unidentate ligands

Answer 10

stays the same at 6

Question 11

Multidentate ligand example

Answer 11

EDTA 4-

Question 12

How many coordinate bonds can multidentate ligands form up to

Answer 12

6

Question 13

explain the Chelate effect

Answer 13

in ligand substitution a positive entropy is favourable because a more stable complex is being formed

this is achieved by substituting unidentate ligands with bidentate or multidentate ligands

the greater the entropy change, the more negative the free energy change will be thus the reaction is more favourable

Question 14

what’s the enthalpy change for ligand substitution reactions like and why

Answer 14

very small
bonds being formed very similar to bonds broken

Question 15

what complexes show cis trans isomerism

Answer 15

octahedral complexes with different types of unidentate ligands

ligands of the same type can be next to each other (cis)
or opposite (trans)

Question 16

what complexes show optical isomerism

Answer 16

octahedral with bidentate ligands the two isomers are mirror images of each other

Question 18

what shows optical isomerism

Answer 18

octahedral complexes with bidentate ligands

Question 19

what 2 transition metal complexes form square planar

Answer 19

Platinum and nickel

Question 20

what is cisplatin

Answer 20

cancer therapy drug
cis isomer of square planar complex platinum
only this orientation ‘fits’ the cell

Question 21

what effects colour of transition metal complexes

Answer 21

coordination number
type of ligand
oxidation state

Question 22

energy change equation

Answer 22

energy change = planks constant x frequency (in hertz)

Question 23

what is an excited state

Answer 23

electrons in the d orbital are given energy and move from ground state to a higher state which is called an ‘excited state’

Question 24

how many oxidation states does vanadium have

Answer 24

4
from +5 to +2

Question 25

colours of vanadium oxidation states

Answer 25

+5 (VO2)+ ——-> yellow +4 (VO)2+ ——-> blue +3 (V)3+ ———> green +2 (V)2+ ———-> violet

Question 26

pneumonic to help with remembering colour of vanadium in decreasing order of oxidation state

Answer 26

You Better Get Vanadium

Question 27

what determines whether a transition metal is oxidised or reduced

Answer 27

the pH of the reaction conditions

Question 28

For ions to be reduced what conditions are needed ?

Answer 28

acidic conditions

Question 29

Give equation for oxidation of (MnO4)-

Answer 29

(MnO4)- + 8H+ + 5e- ———> Mn2+ + 4H2O

Question 30

give equation for oxidation of (Fe)2+

Answer 30

(Fe)2+ ———> (Fe)3+ + e-

Question 31

give equation for (C2O4)2-

Answer 31

(C2O4)2- ———> 2CO2 + 2e-

Question 32

what is a heterogeneous catalyst give an example

Answer 32

a catalyst in a different phase or state to the species in the reaction solid iron catalyst in the haber process

Question 33

why do transition metals make good catalysts

Answer 33

variable oxidation states electrons are transferred to produce a reactive intermediate and speed up reaction rate the contact process is an example which uses vanadium oxide to speed up conversion of Sulfur dioxide to sulfur trioxide

Question 34

describe how a solid catalyst works

Answer 34

it works adsorbed molecules onto an active site on the surface of the catalyst these active sites increase the proximity of molecules and weaken the covalent bonds.

Question 35

what does strength of adsorption depend on

Answer 35

the type of catalyst

Question 36

what is catalyst poisoning

Answer 36

impurities block active sites and prevent adsorption

Question 37

what are homogeneous catalysts

Answer 37

catalysts that are in the same phase to the species in the reaction

Question 38

give an example of a homogeneous catalyst

Answer 38

(S2O8)2- and I- wheee (Fe)2+ is used as a catalyst without it the two negative ions would repel each other and never react

Question 39

overall and intermediate reactions equation for contact process

Answer 39

overall : 2SO2 + O2 ——-> 2SO3 intermediate: V2O5 + SO2 ———-> V2O4 + SO3 V2O4 + 1/2 O2 ——-> V2O5

Question 40

overall and intermediate reaction equations for S2O8 2- + 2I-

Answer 40

Overall: (S2O8)2- + 2I- ———> I2 + (2SO4)2- intermediate (S2O8)2- + 2Fe 2+ ———> 2Fe 3+ + (2SO4)2- (2Fe)3+ + 2I- ————> (2Fe)2+ + I2

Question 41

what is autocatalysis

Answer 41

one of the products can act as a catalyst for the reaction as amount of product increases so does the rate of reaction

Question 42

give an example of autocatalysis include equations

Answer 42

Overall: (2MnO4)- + 16H+ + (5C2O4)2- ————-> (2Mn)2+ + 8H2O + 10CO2 intermediate: (4Mn)2+ + (MnO4)- + 8H+ ——-> (5Mn)3+ + 4H2O (2Mn)3+ + (C2O4)2- ———-> 2CO2 + (2Mn(2+

Question 43

what transition metals form in a square planar complex

Answer 43

platinum and nickel

Question 44

what is cisplatin ?

Answer 44

the cis isomer of a square planar complex of platinum commonly used as a cancer therapy drug only this isomer world because it is in the correct orientation to ‘fit’ the cells

Question 45

what does the colour of a transition metal complex depend on ?

Answer 45

coordination number type of ligand oxidation state

Question 46

give equation for energy change

Answer 46

change in energy = planks constant x frequency