Transition Metals

Question 1

Transition metal definition

Answer 1

Forms at least one stable ion with a partially filled d sublevel

Question 2

Transition metal features

Answer 2

Form complex ions
Coloured ions
Catalytic properties
Variable oxidation states

Question 3

Mono dentate ligands

Answer 3

Each ligand forms 1 coordinate bond

Question 4

Bidentate ligands

Answer 4

Each ligand forms 2 coordinate bonds

Question 5

Multidentate ligands

Answer 5

Each ligand forms 2 or more coordinate bonds

Question 6

Need to know monodentate ligands

Answer 6

Water h2o:
Chloride cl-:
Ammonia :nh3
Cyanide :c-n

Question 7

Need to know bidentate ligands

Answer 7

NH2ch2ch2nh2
Coordinate bonds from the lone pairs on the 2 n

C2o42-
Bonds form between 2 o- atoms

Question 8

EDTA4-

Answer 8

Can form six coordinate bonds
Two from n atoms
Fourth from o- atoms

Question 9

Chelate effect

Answer 9

Large increase in entropy

Question 10

When does chelate effect occur

Answer 10

When a monodentate ligand is substituted by a bidentate or multidentate ligand
Number of moles increase so entropy change is positive

Question 11

Why reaction is thermodynamically favourable

Answer 11

Use gibs equation
>h is zero as six n bonds broken and six n bonds made
<s is positive as entropy change is positive
G<0 so reaction is feasible

Question 12

Heamoglobin

Answer 12

Can make six coordinate bonds
Four between fe2+ and n
One between fe 2+ and globin protein
Space for one more with oxygen
When oxygen has been transported bond is broken and co2 forms a bond to brung back to the lungs
Co makes a stronger bond so could permanently bind which is co poisoning

Question 13

If ligands are next to each other

Answer 13

Cis isomers
Can show optimal isomerism if at least 2 bidentate ligands present

Question 14

If ligands are not next to each other

Answer 14

Trans isomers

Question 15

Visible light

Answer 15

Some colours from white light are absorbed and some transmitted through
Transmitted colours combine to make the visible colour

Question 16

Process of absorbing and transmitting light

Answer 16

The d orbitals split in energy levels
D electrons are promoted to a higher d orbital by absorbing energy in the form of light
The colour transmitted through and observed is the light not absorbed by the compound

Question 17

Equation for change in energy

Answer 17

Change in energy = h(Planck constant 6.26x10-34) x f(frequency of light)
Change in energy = h x c/l
C=speed of light
L= wavelength of light

Question 18

Large change in energy between d subshells

Answer 18

High energy light absorbed to excite electrons (blue and purple)
Red/orange transmitted through

Question 19

Small change in energy between d subshells

Answer 19

Low energy light will be absorbed to excite electrons (red and orange)
Blue and purple will be transmitted

Question 20

Change in colour

Answer 20

Transition metal compounds can change colour
Can be caused by
Change in ligands
Change in oxidation state
Change in coordination number
Change in shape of a complex

Question 21

Calorimetry

Answer 21

Measure the amount of light absorbed when it passes through a sample

Question 22

Heterogenous catalysts

Answer 22

Catalysts is in a different phase to the reactants
Reactants adsorb onto surface of the catalyst
Reaction occurs on the surface of catalyst
Products desorb from surface of the catalyst

Question 23

Catalysts are expensive so

Answer 23

Make it more efficient by increasing surface area or spread catalyst over an inert support medium
Catalyst poisoning can happen though as impurities can block the active sites

Question 24

Need to know heterogenous catalyst examples

Answer 24

Ammonia in haber process
N2 + 3h2 <-> 2nh3
Catalysed by solid iron

Making sulfur trioxide in the contact process
Catalysed by vanadium oxide v2o5
2so2 + o2 <-> 2so3
Steps
1-so2 + v2o5 <-> so3 + v2o4
2-2v2o4 + o2 <-> 2v2o5

Question 25

Homogenous catalysts

Answer 25

Catalysts and reactants are in the same phase
S2o82- + 2I- -> 2so42- + I2
Catalysed by fe2+ ions

1-2fe2+ + s2o82- -> 2so42- + 2fe3+
2- 2fe3+ +2I- -> I2 + 2Fe2+
These could happen in either order

Question 26

Autocatalyst

Answer 26

Where a product of the reaction catalysts the reaction further
16H+ + 2mno4- + 5c2o42- -> 2mn2+ + 8h2o + 10co2
Mn2+ catalyse the reaction further
4mn2+ mno4- + 8h+ -> 5mn3+ + 4h2o
2mn3+ + c2o42- -> 2co2 + 2mn2+

Question 27

Potassium manganate reactions

Answer 27

8h+ + mno4- + 5fe2+ -> mn2+ +4h2o + 5fe3+
When using in titration ratio is always 1:5

Question 28

Reducing vanadium(v) to vanadium(IV)

Answer 28

Zn + 4h+ + 2vo2+ -> zn2+ 2vo^2+ + 2h2o
Yellow to blue
Can look green if there’s some left

Question 29

Reducing vanadium(V) to vanadium(III)

Answer 29

Zn + 4h+ + vo2+ ->zn2+ + v3+ + 2h2o
Yellow to green

Question 30

Reducing vanadium (V) to vanadium(II)

Answer 30

3Zn + 8h+ + 2vo2+ -> 3Zn2+ + 2v2+ + 4h2o
Yellow to purple