Transition Metals Flashcards
1
Q
DEFINE A TRANSITION ELEMENT?
A
A TRANSITION ELEMENT IS A D-BLOCK ELEMENT THAT CAN FORM ATLEAST ONE STABLE ION WITH A PARTIALLY FILLED D-SUBSHELL (ORBITAL).
2
Q
which 2 d-block elements from period 4 are not transition metals (out of the 10)?
A
Scandium and Zinc are not transition elements as they do not form a stable ion with a partially filled d-subshell. scandium’s only ion is sc3+, and that has an electron config of [Ar], hence it has an empty d-subshell which is not partially filled hence its not a transition element.
similarly with zinc it only forms zn2+. zn2+ has a full d-subshell, as its not partially filled hence its not a transition element.
3
Q
how do chromium and copper behave differently in terms of their electron config?
A
an electron from the 4s orbital moves into the 3d orbital to create a more stable half-full or full 3d sub-shell respectively. e.g CR: 1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1 (not 3d4,4s2)
4
Q
give 3 properties for transition metals?
A
variable oxidation states
form coloured complex ions in solution
are good catalysts
5
Q
why do transition metals have variable oxidation states?
A
this is because the electrons sit in 4s and 3d energy levels which are very close.
6
Q
gives the different ions and the colours of these ions for vanadium?
A
v2+ - violet
v3+ - green
VO2+ - blue
vo2 + - yellow
7
Q
colour of cr3+ and cr2o72- (dichromate)
A
cr3+ - green/violet (violet when surrounded by 6h20. they are normally subbed so usually looks green.
cr2o72- (dichromate) - orange
8
Q
colour of mn2+ and mno4-
A
mn2+ - pale pink
mno4- = purple
9
Q
colour of fe2+ and fe3+.
A
fe2+ - pale green
fe3+ - yellow
10
Q
colour of Co2+
A
pink
11
Q
colour of Ni2+
A
green
12
Q
cu2+
A
blue
13
Q
define a complex ion?
A
a complex ion is where a central transition metal ion is surrounded by ligands bonded by dative covalent (coordinate) bonds.
14
Q
define ligand?
A
a species (ion/molecule/atom) with atleast one lone pair of electrons where they are used to form a dative covalent (coordinate) bond with the metal. they can be mono, bi or poly/multi dentate.
15
Q
monodentate (unidentate) ligands are what (define) and give the 3 examples of em’? (that i ned to know)
A
ligands which only have one lone pair of electrons are called monodentate (unidentate) ligands.
examples: h2o:, :NH3, :cl-
16
Q
bidentate ligands are….. (examples give aswell)
A
ligands which have 2 lone pairs of electrons are called bidentate ligands.
eg, ethanedioate (C2O4 2-)
eg, ethane-1,2-diamine (C2H8N2)
17
Q
multidentate ligands are…. (give the examples)
A
ligands which have more than 1 coordinate bond.
eg, haem
eg, EDTA 4- (multidentate as it forms 6 coordinate bonds with the central metal ion)
18
Q
the shape of a ligand is determinded by what?
A
the size of the ligands and the coordination number.
19
Q
the coordation number is …..?
A
the number of coordinate bonds in a complex. (ITS NOT THE NUMER OF LIGANDS!)
20
Q
which ligands are small and you can hence fit 6 of them around a central metal ion?
A
h20: and :Nh3
21
Q
some ligands are larger hence u can only fit 4 of them around the central metal ion. which one (eg)?
A
:cl-
22
Q
for bidentate ligands (larger than that of the monodentate), like ethanedioate and ethane-1,2-diamine, you have how many of these around a central metal ion?
A
3
23
Q
complexes with a coordination number of 6, can form what shape? and whats the bond angle.(give the eg i need to know)
A
octahedral shapes. eg, Co[(h20)6]2+, [(nh3)6]2+. all bond angles in an octahedral complex are 90 degrees.
24
Q
complexes with a coordination number of 4, form what shapes? and whats the bond angle for each shape (give the examples I need to know)
A
form tetrahedral and square planar shapes. bond angles in tetrahedral complex are 109.5 degrees
a specific example of a square planar complex is the anti cancer drug cis-platin (only square planar example i must know). bond angle for cisplatin is 90 degrees.
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25
complexes with a coordination number of 2 form what shapes? give the eg,s
linear shapes. a specific example are some silver complexes. like [Ag(Nh3)2] + (aq) - tollens reagent. bond angle is 180.
26
COMPLEXES HAVE AN OVERALL CHARGE WHICH IS THE SAME AS ITS TOTAL OXIDATION STATE. HOW DO U WORK OUT THE TOTAL OXIDATION STATE OF THE CENTRAL METAL?
TOTAL OXIDATION STATE OF THE COMPLEX - THE TOTAL OXIDATION STATE OF LIGANDS
27
why is carbon monoxide a poisonous gas that causes headaches, unconsciousness and even death, as well as being a silent killer.
if carbnon monoxide (CO) is inhaled, the water ligand bound to the iron (fe) in haemoglobin is replaced with a carbon monoxide ligand.
unfortunately carbon monoxide bonds strongly hence its not readily replaced by oxgen or water.
this means oxygen cant be transported leading to oxygen starvation in organs. hence why carbon monoxide is poisonous.
28
which specifc complexess can show optical isomerism?
octahedral complexes with 3 bidentate ligands show optical isomerism (a type of stereoisoism)- complexes are optical isomers when they are non-superimposable mirror images.
EG:
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29
which specifc complexess can show cis-trans isomerism?
octahedral complexes with 4 ligands of the same type and 2 ligands of a different type diplay cis-trans isomerism. TRANS = OPPOSITE SIDE. CIS = SAME SIDE EG, TRANS [Co(h20)4cl2] Cis-[Co(h20)4 cl2]
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30
what other complex other than octahderal complexes with 4 ligands of the same type and 2 ligands of a different type, can display cis-trans isomerism?
square planar complex ions also show cis-trans isomerism (cisplatin). square planar complexes with 2 ligands of the same type and 2 ligands of a diff type display cis-trans isomerism.
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31
when does the d-subshell split into 2?
when ligands bond with the central metal ion. this is because orbitals/subshells gain energy when ligands are added to central metal ion. hence theres an energy gap between the 2 new d-subshells .
32
when electrons absorb light energy, explain the movement of some of these electrons in terms of energy levels from 1 orbital to another?
when electrons absorb light energy, some move from lowest energy level (ground state) to higher energy level orbitals (excited state)
33
what is required in order for electrons to be able to transist/move from one orbital in a lower energy level to another higher one in energy level?
the 3d-subshell must be partially filled and the energy of the light (energy) must = ΔE.
34
the size of ΔE is dependent on what?
the central metal ion and its oxidation state
the type of ligand
the coordination number
35
in the process of d-orbital splitting, the energy absorbed by the electrons can be calculated using what formula?
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36
SOME FREQUENCIES OF VISIBLE LIGHT ARE _____ BY TRANSITION METAL COMPLEXES. THE FREQUENCIES _____ DEPENDS ON WHAT?
SOME FRQUENCIES OF VISIBLE LIGHT ARE ABSORBED BY TRANSITION METAL COMPLEXES. THE FREQUENICES ABSORBED DEPENDS ON THE SIZE OF ΔE.
37
the larger the energy gap ΔE, the higher the what?
the higher the freqeuncy of light absorbed
38
any frequencies which are not absorbed are _____ or ______
reflected or transmitted
39
the combination of all these frequencies create what?
a complementary colour that we observe with some complexes.
40
eg, [cu(h20)6]2+ absorbs frequencies that produce red light. whats the complemenary colour hence what colour to we observe when it absorbs red light.
the complementary colour is light blue (cyan) so we observe this colour.
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41
for the complexes that have a full or empty 3d sub shell (not transition metal complexes), as mentioned, no electrons can migrate to the higher energy level as there is no space/no electrons at all to migrate.. in terms of the colour we observe, what does this mean? and give eg,
this means we see these complexes as colourless or white.
eg, when scandium or zinc dissolve in water and are surrounded by 6 h2o ligands, they form white/colourless compounds
42
the colour of complex ions depends on what?
the size of ΔE, and hence is depended on the type of ligand, the coordination number and hence the shape of the ligand, the oxidation state of the central metal ion.
43
give an example of ligand sub where the Coordination number and hence the shape stay the same and give an example of a ligand sub where teh coordination number changes and so does the shape.(this happens when a smaller ligand is sub'ed by a larger ligand like cl-)
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44
give examples where oxidation state of the central transition metal changes but the ligands and the coordination numbers stay the same?
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45
transition metal complexes can be analysed using what?
colorimetry which measures the conc of transition metal ions in solution. the colours we see are compliments of the colour absorbed by the solution
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46
a colourimeter measures what?, the more concentrated a sample is, the _____ its colour and hence the more _____ is ______.
colourimeter measures the abosrbance of light by a coloured sample. the more concentrated a sample is, the darker its colour and hence the more light absorbed.
47
in a transition metal sub reaction (like a cobalt complex), when ligands like ammonia and water sub each other.
for eg, [co(h2o)6 ]2+ (aq) +6nh3 (aq) -----> [co(nh3)6 ] 2+ (aq) +6h2o (l) , why does the octahedral shape remain the same?
since there is no change in coordination number and hence no change in shape. which hapens as both ammonia and water are similar sized ligands and have same charges. (both got no charges)
48
give an example reaction where the transition metal substitution is partial. (i.e when cu(h2o)6 reacts with excess ammonia)
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49
give the examples when transition metal complexes react with a larger sized ligand like cl-, (give the colour change aswell)
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50
different ligands can form different what to the metal ion?
different ligands can form different strength bonds to the metal ion.
51
in relation to ligands forming bonding with the central metal ion, when does the complex formed be more stable and give an eg,
when a certain ligand forms stronger bonds than another ligand, this means the reaction becomes not easily reversed. hence the new compex formed is mores stable.
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52
which type of ligands form complexes that are more stable than monodentate ligands? give eg,
multidentate ligands/bidentate ligands form complexes which are more stable than monodentate ligands.
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53
in a ligand exchange reaction, the energy needed to break the bonds (in the original complex) is ______ as the energy released when new ones are formed )in the new complex).hence what does this say about the enthalpy change (ΔH)? and give an example where this is the case in relation to ΔH?
in a ligand exchange reaction/sub, the energy needed to break the bonds in the og complex, is similar to the energy released when the new bonds are formed in the new complex.
this suggests that ΔH is small like in the reaction below:
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54
as entropy increases, what?
a more stable complex forms. (stability of complex increases)
55
increasing entropy and small ΔH, MEANS WHAT IN TERMS OF STABILITY?
MORE STABILITY IN THE COMPLEX.
56
whats the chelate effect. AND GIVE AN EG OF THIS EFFECT USING EDTA 4-
when monodentate ligands are subbed with multi/bi dentate ligands, we create a solution with more particles in it. this means we have an increase in entropy, and so an increase in stability. The increase in stability is known as the chelate effect. (since MORE MOLES ON THE PRODUCT SIDE THEN THE REACTANT SIDE = HIGHER ENTROPY VALUE)
eg:
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57
when a transition metal changes oxidation state, what reaction happens?
a redox reaction occurs
58
vanadium has different oxidation states for its different ions. give the oxidation states of each of its ions.?
v2+ - OS is +2
v3+ - OS is +3
VO 2+ - OS is +4
VO2 + - OS is +5
VIRGIL GOT BELTED YESTERDAY!
59
Vanadium (V) ions (Vo2 +) can be reduced using .what.... all the way to which vanadium ion?
using zinc in an acidic solution (zinc is solid when in the reactant) all the way to Vanadium (II) ions (V2+).
60
Give for equations for all the reduction reactions involving vanadium ions up until v2+? and give the colour changes.
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61
redox potentials tells us how easily an ion is what which is the same as what?
redox potentials tell us how easily an ion is reduced which is the same as electrode potentials.
62
Which is the least stable ion in relation to their redox potential/standard electrode potential value (Eθ) give an eg as well of the least stable ion.
and give the standard conditions required for standard electrode potentials (Eθ) etc....
the least stable ions are the ones which have the largest electrode potential value (Eθ) and hence are more likely to be reduced.
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63
there may be a difference in redox potential/electrode potential to the standard values seen in a data book. what is the redox potential dependent on?
it is dependent on the environment the ions are in. (i.e the conditions required, hence its important to keep the standard conditions as same as possible with minimal change as these can change which makes the redox potential different either higher or lower than the standard electrode potential)
64
that 2 factors affect the size of redox potentials/electrode potentials and explain and elaborate.
the standard electrode potentials are always measured in aqeuous solutions. hence this means the metal ion is surrounded by water molecules.
However the type of the ligand affects the redox potential.
ligands other than water can form stronger bonds to the metal ions with particaular oxidation states. (example with carbon monoxide in replacing the water ligand in haem, as well as CN replacing H20 ligands since it forms stronger bonds with the central metal ion) This means the redox potential can be higher or lower than the standard value.
PH is another factor. the PH of the solution affects the size of the redox potentials with some reactions.
generally the more acidic the solution (i.e the more H+ ions it contains), then the larger the electrode potential, which means the ion is more easily and likely to be reduced.
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Overall, In simple terms, the environment (ligands and pH) can shift how easily a metal ion is reduced in redox reactions.
65
what are redox titrations used for? (instead of finding the conc of an acid or a base)?
find the concentration of a reducing or oxidising agent.
66
in acid base titrations we use indicators to try and identify the end point. how come with redox titrations you need need to add an indicator?
coloured compounds are used since they are transition metals hence no indicator is needed as transition metal ions naturally change colour when changing oxidation state. hence they are said to be 'self-indicating'..
67
give an example of a redox titration, where you are finding the concentration of the reducing agent and titrating the oxidisng agent against the reducing agent.
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68
in the redox titration of mno4- with fe2+ at one point do you know all the fe2+ has been oxidised?
when end point is reached, which is achieved when a purple colour is given off hence its vital to add drop by drop.
69
What happens to potassium manganate(VII) in acidic solution during a redox reaction, and what is the color change observed?
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73
in both redox titration examples, excess sulfuric acid is added to the conical flask with fe2+. why?
to acidify ensure there is sufficient h+ ions to allow the reduction of the oxidising agent.
74
what are the 2 types of catalysts?
homogenous and heterogenous
75
define heterogenous catalyst?
This is a catalyst that is in a different phase from the reactants. the catalyst is in a different state to the reactants.
76
a solid iron catalyst is used in the haber process. N(g)+3H2 (g)⇌ 2NH3 (g). how is this iron catalyst a heterogenous cataylyst?
because its in a different state to the gaseous reactants.
77
increasing the surface area of the heterogenous catalyst does what?
will increase the rate of reaction. hence more particles can react with the catalyst at the same time (larger area for reactions to happen on)
78
define homogenous catalyst?
catalysts that are in the same phase as the reactants. generally homogenous catalysts are aqeuous in aqeuous reactants. eg using h2so4 to make ester.
79
homogenous catalysts FORM intermediate species by doing what? (how do HOMOGENOUS CATALYSTS WORK)
THEY WORK BY COMBINING WITH REACTANTS TO FORM INTERMEDIATE SPECIES WHICH THEN REACT TO FORM PRODUCTS AND A REFORMED CATALYST
80
why are transition metals good catalysts?
because they have variable oxidation states, hence are good at receiving and losing electrons in the d-orbitals to speed up reactions
81
whats the contact process?
process which involves using V2O5 (VANADIUM V) as catalyst to catalyse SO2 TO SO3 to make sulfuric acid. THIS IS A HETEROGENOUS CATALYST.
82
give the equations during the contact process.
v2o5 + so2 -----> v2o4 +so3
v2o4 +1/2O2 ----> v2o5
83
why are catalysts used in the manufucture of products?
to make product faster and can be used to lower the temp required for a reaction.
HENCE SAVING MONEY AND ENERGY.
84
whats the limitation of heterogenous catalysts?
they can be poisoned by impurities
85
how do impurities cause catalytic poisoning, and hence slow down the rate of reaction?
impurities bind to the surface of a catalyst and block the actives sites for reactants to adsorb.
when an impurity blocks a site this is known as poisoning.
hence catalytic poisoning reduces the surface area of the catalyst for the reactants to add to, hence slowing down the reaction.
86
in the haber process, since we know a solid iron catalyst is used, the hydrogen is made from methane. and methane contains sulfur impurities. what can occur and what does this lead to? (WHAT OUTCOMES RESULT IN A POSIONED CATALYST BEING PRODUCED)
since sulfur impurities are present, any sulfur that is not removed will adsorb to the surface of solid iron catalyst, forming iron sulfide and blocking the active site of the catalyst, hence poisoning the catalyst, making it less efficient.
A POISONED CATALYST THEN MEANS:
LESS PRODUCT IS MADE
THE CATALYST NEEDS TO BE REPLACED OR CLEANED MORE OFTEN
INCREASED COST OF THE CHEMICAL PROCESS
87
THE REACTION OF S2O8 2- + 2I- ------> I2 + 2SO4 2- WHILE BEING UNCATALYSED HAS A HIGH ACTIVATION ENERGY, WHY?
NEGATIVELY CHARGED IONS ARE TRYING TO REACT TOGETHER, HOWEVER REPEL. SO THE REACTION IS VERY SLOW HENCE THERE IS A VERY HIGH ACTIVATION ENERGY.
88
WHAT DO WE USE AS A CATALYST TO LOWER THE ACTIVATION ENERGY AND SPEED UP THE REACTION IN THIS REACTION:S2O8 2- + 2I- ------> I2 + 2SO4 2- AND GIVE THE EQUATIONS.
FE2+ IS USED AS A CATALYST TO LOWER THE ACTIVATION ENERGY AND SPEED UP THE REACTION. THE 1ST PART IS THE REDUCTION OF S208 2-, AND THE SECOND PART IS THE REFORMATION OF THE ORIGINAL FE2+ USED (AS CATALYST NEVER RUN OUT), BY REACTING IT WITH I- IONS.
EQUATIONS:
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GIVE THE DIAGRAM FOR THE ENeRGY PROFILE IN GENERAL AS WELL SHOWING THE ALTERNATIVE REACTION PATHWAY PROVIDED bY IRON(II) catalyst in the reaction between iodide ions and peroxodisulfate ions.
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DEFINE AUTOCATALYSIS? AND GIVE THE EG OF IT
ANOTHER FORM OF HOMOGENOUS CATALYSIS, BUT THE PRODUCT OF THAT REACTION CATALYSES ITSELF.
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