✅15 - Transition Metals Flashcards
1
Q
Where are transition metals found in the periodic table?
A
D block
2
Q
What are transition metals?
A
D block elements that can form one or more stable ions with incompletely filled d-orbitals
3
Q
Which d block period 4 elements are not transition metals?
A
Scandium and Zinc
4
Q
How many electrons can the d orbital hold?
A
10
5
Q
When ions are formed, which electrons are removed first?
A
The s electrons
6
Q
Why is Scandium not a transition metal?
A
It only forms one ion, Sc3+, which has an empty d subshell
7
Q
Why is zinc not a transition metal?
A
It only forms one ion, Zn2+, which has a full d subshell
8
Q
How many stable oxidation states does Vanadium have?
A
4
9
Q
What are the stable oxidation states of Vanadium?
A
II, III, IV, V
10
Q
What do transition metals have?
A
Variable oxidation states
11
Q
What conditions must be met to form a compound of complex with an ion of a certain oxidation number?
A
The energy given out when the ion forms a compound or complex needs to be greater than the ionisation energy
12
Q
How do transition metals form ions?
A
By loosing electrons from their 4s and 3d subshells
13
Q
When does the energy released when an ion forms a complex or compound increase?
A
When the ionic charge increases.
14
Q
What are complex ions?
A
Metal ions surrounded by datively covalently bonded ligands
15
Q
What is a ligand?
A
An atom, ion or molecule which donates a pair of electrons to a central metal atom or ion.
16
Q
What are monodentate ligands?
A
Ligands with one lone pair
17
Q
What are bidentate ligands?
A
Ligands with two lone pairs
18
Q
What are multidentate ligands?
A
Ligands with more than two lone pairs
19
Q
What are examples of monodentate ligands?
A
H2O, NH3, Cl-
20
Q
What is an example of a multidentate ligands?
A
EDTA 4-
21
Q
What is the name for water in a complex?
A
Aqua
22
Q
What is the name for a hydroide group in a complex?
A
hydroxo
23
Q
What is the name for ammonia in a complex?
A
Ammine
24
Q
What is the name for chloride in a complex?
A
Chloro
25
How many colours traditionally make up white light?
7
26
Why are transition metal complexes coloured?
Electrons split into two energy levels when ligands attach. If an electron absorbs light, it can move to a higher energy level, and the light reflected is the colour seen
27
With 6 ligands, what shape is a complex?
Octahedral
28
With 4 ligands, what shape is a complex?
Tetrahedral or square planar
29
With 2 ligands, what shape is a complex?
Linear
30
What is an example of a linear complex?
Tollen's reagent
31
What is cis-platin?
An anti-cancer drug which has a square planar shape
32
What does a cis- prefix indicate?
That the identical ligands are next to each other
33
What does a trans- prefix indicate?
That the identical ligands are opposite each other
34
How does cis-platin kill cancer cells?
It forms a bond between the two strands of DNA which prevents them from separating, and therefore prevents replication
35
How is trans-platin different to cis-platin?
It is toxic and much less effective at targeting cancer
36
Why does reducing the number of ligands increase stability?
The system becomes more disordered and there is an increase in ∆S system
37
What causes the greatest increase in stability?
Exchanging a monodentate ligand for a multidentate ligand
38
How is Fe held in haemoglobin?
By forming dative bonds with four nitrogens in the structure, in a square planar
39
What else is bonded to the Fe in haemoglobin?
Globin (a protein) and Oxygen
40
Why is carbon monoxide poisonous?
Because the dative bond between carbon monoxide and haemoglobin is stronger than with oxygen, so any CO breathed in will bins with the haemoglobin and not break easily
41
What is the equation for the reaction between aqueous NaOH and copper(II) sulfate solution?
[Cu(H2O)6]2+ + 2OH- ---> [Cu(H2O)4(OH)2] + H2O
42
What colour is [Cu(H2O)4(OH)2]?
Blue precipitate
43
What is the equation for the reaction between aqueous ammonia and copper (II) sulfate?
[Cu(H2O)6]2+ + NH3 ----> [Cu(H2O)4(OH)2] + 2NH4+
44
What is the equation for the reaction between the blue copper precipitate and aqueous ammonia?
[Cu(H2O)4(OH)2] + 4NH3 ----> [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-
45
What colour is [Cu(NH3)4(H2O)2]2+?
Deep blue solution
46
What is the equation for the reaction between copper (II) sulfate solution and conc HCl?
{CU(H2O)6]2+ + 4Cl ----> [CuCl4]2- + 6H2O
47
What is the colour change when hydrochloric acid is added to copper sulfate solution?
Blue to green to yellow
48
What is the equation for the reaction between hexaaquacobalt(II) and aqueous sodium hydroxide?
[Co(H2O)6]2+ + 2OH- ----> [Co(H2O)4(OH)2] + 2H2O
49
What is the colour change when sodium hydroxide is added to hexaaquacobalt(II)?
Pink solution to blue precipitate
50
How many reactions occur between hexaaquacobalt(II) and ammonia?
2
51
What is the acid-base reaction between hexaaquacobalt(II) and NH3?
[Co(H2O)6]2+ + 2NH3 ----> [Co(H2O)4(OH)2] + 2NH4+
52
What is the equation for the reaction between [Co(H2O)4(OH)2] and NH3?
[Co(H2O)4(OH)2] + 6NH3 ----> [Co(NH3)6]2+ + 4H2O + 2OH-
53
What is the colour change between hexaaquacobalt(II) and ammonia?
Precipitate dissolves to a brown solution
54
What is the colour od the [Co(NH3)6]3+ ion?
Yellow
55
What is the equation for the reaction between hexaaquacobalt(II) and conc HCl?
[Co(H2O)6]2+ + 4Cl- ----> [CoCl4]2- + 6H2O
56
What is the colour change when conc HCl is added to the hexaaquacobalt (II) solution?
Pink to blue
57
What is the equation for the reaction between hexaaquairon(II) and sodium hydroxide?
[Fe(H2O)6]2+ + 2OH- ----> [Fe(H2O)4(OH)2] + 2H2O
58
What is the colour change in the reaction between hexaaquairon(II) and sodium hydroxide?
Pale green solution forms a green precipitate
59
What is the equation for the reaction between hexaaquairon(II) and NH3?
[Fe(H2O)6]2+ + 2NH3 ----> [Fe(H2O)4(OH)2] + 2NH4+
60
What is the equation for the reaction between hexaaquairon(III) and sodium hydroxide?
[Fe(H2O)6]3+ + 3OH- ----> [Fe(H2O)3(OH)3] + 3H2O
61
What is the colour change for the reaction between hexaaquairon(III) and sodium hydroxide?
Yellow-brown solution forms and brown precipitate
62
What is the equation for the reaction between hexaaquairon(III) and NH3?
[Fe(H2O)6] + 3NH3 ----> [Fe(H2O)3(OH)3] + 3NH4
63
What are the colours shown by chromium compounds affected by?
Some compounds have different colours as solids and aqueous solutions
The colour of the solution depends on the concentration
The presence of dissolved oxygen in an aqueous solution can affect the colour seen
64
What is the equation for the reaction between the hexaaquachromium(III) ion and aqueous sodium hydroxide?
[Cr(H2O)6]3+ + 3OH- ----> [Cr(H2O)3(OH)3] + 3H2O
65
What is the colour change for the reaction between hexaaquachromium(III) and sodium hydroxide?
Green or violet solutions forms a green precipitate
66
What is the equation for the reaction between hexaaquachromium(III) and NH3?
[Cr(H2O)6]3+ + 3NH3 ----> [Cr(H2O)3(OH)3] + 3NH4+
67
What happens to the precipitate [Cr(H2O)3(OH)3] when it is dissolved?
It dissolves to form a green solution of [Cr(H2O)2(OH)4]-
68
What happens to the precipitate [Cr(H2O)3(OH)3] when excess ammonia is added?
It is slow to dissolve but eventually a violet or purple solution of [Cr(NH3)6]3+ forms
69
What is the equation for the reaction between [Cr(OH)6]3- and hydrogen peroxide?
2[Cr(OH)6]3- + 3H2O2 ----> 2CrO42- + 2OH- + 8H2O
70
What is the colour change for the reaction between the chromium complex and hydrogen peroxide?
Green solution to yellow solution
71
What is hydrogen peroxide?
An oxidising agent
72
How does the chromate ion change with acidity?
In alkaline solution, the chromate(VI) ions are stable, but in acidic solution the dichromate(VI) are most stable
73
What colour change is seen if acid is added to chromate ions?
Yellow to orange
74
What can dichromate(VI) ions be reduced by?
Zinc
75
What is the equation for the reduction of dichromate ions using zinc?
Cr2O72- + 14H+ +3Zn ----> 2Cr3+ + 7H2O + 3Zn2+
76
What is the colour change when dichromate ions are reduced?
Orange to green
77
What is the colour change when Cr3+ is reduced to Cr2+?
Green to blue
78
What reaction happens when NaOH is added to [Cr(H2O)3(OH)3]?
It forms [Cr(OH)6]3-
79
What colour are V2+ ions?
Purple
80
What colour are V3+ ions?
Green
81
What colour are (VO)2+ ions?
Blue
82
What colour are (VO2)+ ions?
Yellow
83
In what compound does vanadium have a +4 oxidation number?
(VO)2+
84
In what compound does vanadium have a +5 oxidation number?
(VO2)+
85
Why is it easy to demonstrate a change in oxidation number with vanadium?
Because its colour changes are so distinctive
86
What can be used to reduce vanadium from +5 to +2?
Zinc
87
What is the equation for the reduction of vanadium from +5 to +4?
2(VO2)+ + 4H+ + Zn ----> 2(VO)2+ + Zn2+ + 2H2O
88
What is the equation for the reduction of vanadium from +4 to +3?
2(VO)2+ + 4H+ + Zn ----> 2V3+ + Zn2+ + 2H2O
89
What is the equation for the reduction of vanadium from +3 to +2?
2V3+ + Zn ----> 2V2+ + Zn2+
90
What is the equation for the reduction of vanadium from +2 to 0?
2V2+ + Zn ----> 2V + Zn2+
91
Which of the vanadium reductions is not thermodynamically feasible?
+2 to 0
92
In what state are transition metals usually used as catalysts?
Solid, as a powder
93
What is the catalyst in the contact process?
V2O5 - Vanadium Pentoxide
94
What are the steps of surface adsorption theory?
Adsorption
Reaction
Desorption
95
What is adsorption?
One or more reactants become attached to the catalyst
96
What is the reaction step in surface adsorption theory?
Following the weakening of the bonds in the adsorbed reactants
97
What is desorption?
The reaction product becomes detached from the surface of the catalyst
98
What are the reactions that occur on the surface of vanadium in the contact process?
V2O5 + SO2 ----> V2O4 + SO3
| V2O4 + 0.5O2 ----> V2O5
99
What are the problems tackled by catalytic converters?
Increased pollution levels
Carbon monoxide emissions
Nitrogen monoxide emissions
100
What are the transition metals used in catalytic converters?
Platinum and rhodium, sometimes palladium
101
What is the equation for the reaction between Carbon monoxide and nitrogen monoxide?
2CO + 2NO ----> 2CO2 + N2
102
Why does the reaction between CO and NO occur on catalytic converters?
Because the molecules of CO and NO are adsorbed and then, because their bonds are weakened, they react together to form CO2 and N2, which are then desorbed
103
What is a key feature of homogeneous catalysts?
The formation of an intermediate species for which a specific formula can be written
104
What is the equation for the reaction between persulfate ions and iodide ions?
S2O82- + 2I- ----> 2SO42- + I2
105
What is the catalyst in the reaction between iodide and persulfate ions?
Fe2+
106
What are the steps in the reaction between I- and S2O82-?
S2O82- and 2Fe2+ react together to form 2SO42- and 2Fe3+
| 2Fe3+ react with 2I- to form 2Fe2+ and I2
107
Why do the Fe2+ and S2O82- react together?
Because they do not repel each other, as they have the opposite charge
108
What is the alternative mechanism for the reaction between I- and S2O82-?
2Fe3+ + 2I- ----> 2Fe2+ + I2
| S2O82- + 2Fe2+ ----> 2SO42- + 2Fe3+
