Transition metals

Question 1

What is a transition metal?

Answer 1

Incomplete d sub-shell

Question 2

define ligand

Answer 2

an atom ion or molecule which can donate a lone electron pair

Question 3

co-ordinate bonding definition

Answer 3

when the shared pair of electrons in the covalent bond come from only one of the bonding atoms

Question 4

co-ordination number definition

Answer 4

the number of co-ordinate bonds formed to a central metal ion

Question 5

monodentate ligand defininton and examples

Answer 5

form one co-ordinate bond per ligand
h2o, nh3, cl-

Question 6

bidentate def and examples

Answer 6

has two atoms with lone pairs and can form two coordinate bonds per ligand
e.g. NH2CH2CH2NH2 or C2O4 2-

Question 7

multidentate def and example

Answer 7

forms more than 2 coordinate bonds per ligand
e.g. EDTA 4-

Question 8

exchange of NH3 and H2O ligands

Answer 8

• since they are similar in size and are both uncharged, exchange doesnt change coordination number
• however it may be incomplete

Question 9

equation for complete exchange of H2o and nh3 ligands

Answer 9

[Co(H2O)6] 2+ + 6NH3 –> [Co(NH3)6] 2+ + 6H2O

Question 10

equation for incomplete exchange of H2O and NH3 ligands

Answer 10

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

Question 11

reactions with chloride ions theory q

Answer 11

• adding a high conc of chloride ions to an aqueous ion leads to a ligand substitution reaction
• the cl- ligand is larger than the H2O or NH3 ligand, and so the exchange may change coordiation number

Question 12

general formula for the addition of conc HCL to aqueous TMsq

Answer 12

[X(H2O)6] 2+ + 4CL- —> [XCl4] (charge -4) + 6H2O

Question 13

TM chloride + water

Answer 13

becomes the AQUEOUS [X(H2O)6]2+

Question 14

formation of bidentate ligands

Answer 14

Ethane-1-2-diamine:
[Cu(H2O)6]2+ + 3NH2CH2CH2NH2 –> [Cu(NH2CH2CH2NH2)3]2+ + 6H2O

Ethanedioate:
[Cu(H2O)6]2+ + 3C2O4 2- –> [Cu(C2O4)3] 4- + 6H2O

Question 15

when does partial substitution of ethanedioate ions occur

Answer 15

dilute aqueous solution is added to a soution containing aqueous copper 2 ions

Question 16

formula for partial sibstitution of ethanedioate ions

Answer 16

must be copper 2

[Cu(H2O)6]2+ + 2C2O4 2- –> [Cu(C2O4)2(H2O)2]2- + 4H2O

Question 17

formula of edta complexes

Answer 17

[Cu(H2O)6]2+ + EDTA 4- –> [Cu(EDTA)]2- + 6H2O

Question 18

what causes colour changes

Answer 18

changes in:
- oxidation state
- co-ordination number
- ligand

Question 19

transition metal + NaOH

Answer 19

if 2+ :
[X(H2O)6]2+ + 2OH- –> X(H2O)4(OH)2 + 2H2O

if 3+ :
[x(H2O)6]3+ + 3OH- –> X(H2O)3(OH)3 + 3H2O

Question 20

colour: copper 2+ complex + NaOH

Answer 20

light blue solution to blue precipitate

Question 21

colour: iron 2+ complex + NaOH

Answer 21

pale green solution to green precipitate

Question 22

colour: iron 3+ complex + NaOH

Answer 22

orange / brown solution to orange / brown precipitate

Question 23

colour: aluminium 3+ complex + NaOH

Answer 23

colourless solution to white precipitate
in excess NaOH, the white precipitate will redissolve to form a colourless solution
- Al(H2O)3(OH)3 + 3OH- –> [Al(OH)6]3- + 3H2O

Question 24

transition metal complex + ammonia

Answer 24

If 2+ :
[X(H2O)6]2+ + 2NH3 –> X(H2O)4(OH)2 + 2NH4+

IF 3+ :
[X(H2O)6]3+ + 3NH3 –> x(H2O)3(OH)3 + 3NH4+

Question 25

colour: copper 2+ complex + NH3

Answer 25

light blue solution to blue precipitate

Question 26

colour: iron 2+ complex + NH3

Answer 26

green solution to green precipitate

Question 27

colour: iron 3+ complex + NH3

Answer 27

orange / brown solution to brown precipitate

Question 28

colour: aluminium 3+ complex + NH3

Answer 28

colourless solution to white precipitate that doesn't redissolve in excess

Question 29

transition metal complex + Na2CO3 (carbonate)

Answer 29

if 2+ : [X(H2O)6] 2+ + CO3 2- --> XCO3 + 6H2O IF 3+ : 2 [X(H2O)6]3+ + 3CO3 2- --> 2X(H2O)3(OH)3 + 3H2O + 3CO2 bubbles seen (CO2)

Question 30

colour: aluminium 3+ complex + carbonate

Answer 30

colourless solution to white precipitate

Question 31

colour: iron 3+ complex + carbonate

Answer 31

brown solution to brown precipitate

Question 32

colour: copper 2+ complex + carbonate

Answer 32

blue solution to green precipitate

Question 33

colour: iron 2+ complex + carbonate

Answer 33

green solution to green precipitate

Question 34

ligand substitution reaction : no change in charge or co-ordination

Answer 34

substitute ammonia with water [Co(H2O)6]2+ + 4NH3 --> [Co(NH3)4(H2O)2] 2+ + 4H2O

Question 35

ligand substitution reaction : change in charge and co-ordination

Answer 35

water / ammonia to chloride [Co(H2O)6]2+ + 4Cl- --> [CoCl4]2- + 6H2O

Question 36

ligand substitution reaction : change in charge number only

Answer 36

substitute for ethanedioate [Co(H2O)6]2+ + 3C2O4 2- --> [Co(C2O4)3]4- + 6H2O

Question 37

ligand substitution reaction : large entropy change

Answer 37

substitute for EDTA [Co(H2O)6] 2+ + EDTA 4- --> [CoEDTA] 2- + 6H2O