Transition Metals- (a)

Question 1

Three properties of transition metals

Answer 1

Form coloured compounds
Good catalysts
Form ions of variable oxidation states

Question 2

Definition of a tranistion metal

Answer 2

Have an incomplete d subshell

Question 3

Which is filled and emptied first, 3d or 4s

Answer 3

4s

Question 4

Name and explain 2 instances where 4s and 3d filling patterns deviate

Answer 4

Chromium [Ar] 4s1 3d5. More stable to have 3d5 than 4

Copper [Ar] 4s1 3d10 more stable tp have 3d10 than 3d9

These two also empty 4s1 before 3d

Question 5

What is a ligand

Answer 5

Molecule or ion that forms a coordinate bond with a transition metal by donating a pair of electrons

Question 6

What is a coordination number

Answer 6

Number of coordination bonds formed by a transition metal

Question 7

Compare and contrast the sizes of ligands NH3, H2O and Cl- and the number of bonds they form with metal ions

Answer 7

NH3 and H2O are similar in size and smaller than Cl-.
The size of these ligands mean that normally 6 NH3 or H2O ligands can be placed around a metal ion but only 4 Cl-

Question 8

Draw the specific shape of 1,2- diaminoethane as a bidentate ligand

Answer 8

see image

Question 9

Draw the specific shape of Ethane Dioate as a bidentate ligand

Answer 9

see image

Question 10

Draw the specific shape of EDTA as a multidentate ligand

Answer 10

see image

Question 11

Draw and name the structure of cis-platin

Answer 11

see image

Question 12

What happens when a small amount of ammonia is added to hexaaqua copper ions

Answer 12

Ammonia acts as proton acceptor
To form some OH ligands
Light blue ppt forms

Question 13

What happens when more ammonia is added to hexaquacopper ions that have formed a light blue solution

Answer 13

OH become H2O ligands
previous waters are substituted
Partial substitution of water to ammonia
Deep blue solution formed

Question 14

Write two equations to represent the adding of ammonia to cause partial substitution of water in hexaaquacopper ions

Answer 14

Cu(h2o)4(OH)2 +4NH3> [Cu(NH3)4(H2O)2]2+ + 2OH- + 2H2O

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

Question 15

What happens what happens when hexaquacopper ions react with chloride ions

Answer 15

6 waters are substituted for 4Cl- ions
Colour change from blue solution to yellow (or green from mixing) solution
Change in charge from 2+ to 2-
Change in Coordination number from 6 to 4

Question 16

Write an equation for when hexaquacopper ions react with Cl- ions and a substitution reaction occurs

Answer 16

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

Question 17

What happens when hexacobaltaqua ions react with chloride ions

Answer 17

Change in colour from pink to blue (solution)
6 waters are substituted for 4Cl- ions
Change in Coordination number from 6 to 4

Question 18

Write an equation for the reaction of hexacobaltaqua ions with chloride ions

Answer 18

[Co(H2O)6]2+ +4Cl- > [Co(Cl)4]2- + 6H2O

Question 19

What is the structure of haemoglobin (and draw picture)

Answer 19

Compare picture to online image
Structure:
Fe with 6 ligands atatched
4 nitrogen groups
one globin group (bonded via N)
Sixth is oxygen when being transported which is lost and substituted by water at the cells

Question 20

Why does CO poisoning kill you

Answer 20

CO forms strong bonds with Fe and is not readily substituted so oxygen cannot be transported around the body

Question 21

Which form more stable complexes, multidentate or monodentate ligands

Answer 21

mULTIDENTATE

Question 22

What is the enthalpy change when in a substitution reaction the coordination number stays the same

Answer 22

negligible

Question 23

In what type of substitution reaction is enthalpy change higher (give examples)

Answer 23

WHen less bonds are made than broken
i.e. Cl substitutes H2O

Question 24

What happens to entropy when multidentate ligands replace monodentate ligands (and explain)

Answer 24

Entropy increases
There are now more particles on products side than reactants side
This means the reaction is more likely to occur

Question 25

Describe the chelate effect

Answer 25

Entropy always increases when multidentate ligands replace monodentate ligands
Using gibbs free energy equation, when delta G is more negative the reaction is more feasible
This explains why multidentate ligands form more stable complexes than monodentate ligands

Question 26

Colour of [Co(H2O)6]2+

Answer 26

pINK

Question 27

Colour of [Co(NH3)6]2+

Answer 27

sTRAW

Question 28

Colour of CoCl4]2-

Answer 28

Blue