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AQA A-LEVEL CHEMISTRY > Transition metals and rxn's of aq ions > Flashcards

Transition metals and rxn's of aq ions Flashcards

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1
Q

ligand

A

molecule/ion w l.p of e- that forms co-ordinate bonds w metals (lewis base = e- lp donor)

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2
Q

complex

A

central metal atom/ion w co-ordinately bonded ligands

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3
Q

monodentate NH3 substitution rxn w hexaqua Co2+ ion eqn

CON

A

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

no change in CON (6) neutral ligands

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4
Q

monodentate NH3 substitution rxn w hexaqua Cu2+ ion eqn

CON
colour change

A

incomplete substitution

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

from blue sol to deep blue sol
no change in CON (6) neutral ligands

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5
Q

monodentate Cl- substition rxn w hexaqua Cu2+ eqn

CON
colour change
shape change

A

[Cu(H₂O)6]²+ + 4Cl- –> [CuCl4]²- + 6H₂O
blue sol to yellow sol

CON changes from 6 to 4 as Cl- are larger and only 4 can bond to metal ion
octahedral to tetrahedral

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6
Q

monodentate Cl- substition rxn w hexaqua Co2+ eqn

CON
shape change

A

[Co(H₂O)6]²+ + 4Cl- –> [CoCl4]²- + 6H₂O

CON changes from 6 to 4 as Cl- are larger and only 4 can bond to metal ion
octahedral to tetrahedral

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7
Q

monodentate Cl- substition rxn w hexaqua Fe3+ eqn

CON
colour change
shape change

A

[Fe(H₂O)6]3+ + 4Cl- –> [FeCl4]- + 6H₂O

violet sol to yellow sol
CON changes from 6 to 4 as Cl- are larger and only 4 can bond to metal ion
octahedral to tetrahedral

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8
Q

monodentate Cl- substition rxn w hexaqua Al3+ eqn

CON
colour change
shape change

A

[Al(H₂O)6]3+ + 4Cl- –> [AlCl4]- + 6H₂O

colourless sol to colourless sol
CON changes from 6 to 4 as Cl- are larger and only 4 can bond to metal ion
octahedral to tetrahedral

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9
Q

bidentate ligand substitution rxn w ethane-1,2-diamine and hexaqua Cu eqn

CON

A

[Cu(H₂O)6]²+ + 3NH₂CH₂CH₂NH₂ –> [Cu(NH₂CH₂CH₂NH₂)3]²+ + 6H₂O

no change in CON as there’s 3 ligands and each forms 2 coordinate bonds so 3x2=6

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10
Q

bidentate ligand substitution rxn w ethanedioate and hexaqua Cu eqn

CON

A

[Cu(H₂O)6]2+ + 3C₂O4²- –> [Cu(C₂O4)3]4- + 6H₂O

no change in CON as there’s 3 ligands and each forms 2 coordinate bonds so 3x2=6

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11
Q

multidentate ligand substitution rxn w EDTA4- and hexaqua Cu eqn

charge?

A

[Cu(H₂O)6]²+ + EDTA4- –> [Cu(EDTA)]²- + 6H2O

2+ + 4- = -2 charge change

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12
Q

small ligands (H₂O and NH3) complex shape, CON, angles, isomerism and give an eg

A

octahedral shape
CON 6
90 adjacent ligands, 180 opp
CisTrans isomerism eg. [CrCl₂(H₂O)4]+

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13
Q

bidentate ligands isomerism

A

optical isomerism
pair of enantomers - arrangement of 2 coordinate bonds for each ligand resulting in non superimposable mirror images

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14
Q

chelate effect
eg.
enthalpy change is aprox 0 why?
how does the rxn occur?

A

substitution of monodentate w bi/multidentate ligand results in more stable complex

eg. [Cu(NH3)4(H2O)2]2+ + 2 NH2CH2CH2NH2 –> [Cu(NH2CH2CH2NH2)2(H2O)2]
2+ + 4NH3

Cu–N bonds formed have similar enthalpy
same number of bonds broken and made

entropy change is positive. 3 to 5 molecules, disorder inc bc more
particles formed
free-energy change is -ve

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15
Q

Larger ligand Cl- shape, CON, angle

A

tetrahedral 109.5
CON 4

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16
Q

Pt²+ and Ni+ complexes shapes, CON, angle, isomerism

A

square planar 90
CON 4
CisTrans isomers - eg. Cisplatin and Transplatin

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17
Q

Ag+ complexes shape, CON, angle

A

Linear
CON 2
180
eg. [Ag(NH3)₂]+ in tollens reagent

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18
Q

vanadium Oxidation state +5 colour

A

VO₂+
yellow solution (you)

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19
Q

vanadium Oxidation state +4 colour

A

VO²+
blue solution (better)

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20
Q

vanadium Oxidation state + 3 colour

A

V 3+
green solution (get)

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21
Q

vanadium Oxidation state +2 colour

A

V²+
violet solution (vanadium)

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22
Q

effect of ligands on redox potential

A

standard electrode potentials measured in aq sol –> ions surrounded by water ligands.
other ligands make RP larger/smaller depends on how well they bind to metal ion

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23
Q

effect of pH on redox potential

A

easier to oxidise in alkaline conditions
easer to reduce in acidic conditions

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24
Q

reduction of [Ag(NH3)₂]+ to metallic silver half eqn

A

[Ag(NH3)₂]+ + e- –> Ag + 2NH3

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25
ox half eqn of aldehyde (ethanal) to ___
carboxylic acid (ethanoic acid) CH3CHO + H2O --> CH3COOH + 2H+ + 2e-
26
redox eqn: MnO4- in acidic conditions - which acid is used
dilute H2SO4 not HCl - MnO4- would oxidise Cl- to Cl2 --> would affect vol KMnO4 req (smaller) not conc H2SO4 or HNO3 - theyre ox agents --> would affect vol of KMnO4 req (smaller) not CH3COOH - weak so wont provide the 8H+ req
27
Fe2+ with MnO4- redox titration overall eqn
5Fe2+ + MnO4- + 8H+ --> 5Fe3+ + Mn2+ + 4H2O purple to colourless
28
if Fe (0) used to redox titration w MnO4-
react Fe (0) w H2SO4 to oxidise it to Fe2+
29
if Fe (3+) used to redox titration w MnO4-
react Fe (3+) w Zn to reduce it to Fe2+
30
C2O4 2- (forms 2 CO2) with MnO4- (forms Mn 2+) redox titration overall eqn
2MnO4- + 16H+ + 5C2O4 2- --> 10CO2 + 2Mn 2+ + 8H2O
31
V2O5 (heterogeneous catalyst) in contact process eqns
overall: 2SO2 + O2 --> 2SO3 step 1: SO2 + V2O5 --> SO3 + V2O4 step 2: 2V2O4 + O2 --> 2V2O5
32
I- and S2O8 2- catalysed by Fe2+ (homogeneous catalyst) rxn eqns why is rxn slow before cat added why Zn2+ dont catalyse rxn
overall: S2O8 2- + 2I- --> 2SO4 2- + I2 step 1: 2Fe 2+ + S2O8 2- --> 2Fe 3+ + 2SO4 2- step 2: 2Fe 3+ + 2I- --> 2Fe 2+ + I2 2 -ve ions repel = high Ea Zn ions hv only 1 oxidation state, Zn2+ is the only ion
33
ox eqn C2O4 2- to 2 CO2
C2O4 2- --> 2CO2 + 2e-
34
[Fe(H2O)6]2+ colour
green sol
35
[Cu(H2O)6]2+ colour
blue sol
36
[Al(H2O)6]3+ colour
colourless sol
37
[Fe(H2O)6]3+ (s) colour
pale violet seen in solid hydrated salts that contain these complexes
38
[Fe(H2O)6]3+ in soloution colour
yellow brown sol due to hydrolysis
39
hexa aqua cu 2+ rxn w limited OH- (from NaOH) Type of rxn OH acts as what and why
[Cu(H2O)6]2+ (aq) + 2OH- (aq) --> Cu(OH)2(H2O)4 (s) + 2H2O (l) blue sol to blue ppt formed deprotonation acid-base rxn OH- acts as BL base (accepts H+)
40
hexa aqua iron (II) rxn w limited OH- (from NaOH)
[Fe(H2O)6]2+ (aq) + 2OH- (aq) --> Fe(OH)2(H2O)4 (s) + 2H2O (l) green sol to green ppt formed deprotonation acid-base rxn OH- acts as BL base
41
hexa aqua iron (III) rxn w limited OH- (from NaOH)
[Fe(H2O)6]3+ (aq) + 3OH- (aq) --> Fe(OH)3(H2O)3 (s) + 3H2O (l) pale violet sol to brown ppt deprotonation acid-base rxn OH- acts as BL base
42
hexa aqua Al 3+ rxn w limited OH- (from NaOH)
[Al(H2O)6]3+ (aq) + 3OH- (aq) --> Al(OH)3(H2O)3 (s) + 3H2O (l) colourless sol to white ppt deprotonation acid-base rxn OH- acts as BL base
43
Al(H2O)3(OH)3 rxn w excess OH- alkali (from NaOH)
Al(H2O)3(OH)3 (s) + OH- (aq --> [Al(OH)4]- (aq) 3 H2O white ppt to colourless sol re-dissolves to give colourless sol amphoteric - here acts as acid
44
Al(H2O)3(OH)3 rxn w excess acid
Al(H2O)3(OH)3 (s) + 3H+ (aq) --> [Al(H2O)6]3+ (aq) white ppt to colourless sol amphoteric - here acts as a base
45
hexa aqua Cu2+, Fe2+, Fe3+ rxn w excess OH- (from NaOH)
no further rxn
46
hexa aqua cu 2+ rxn w limited NH3
[Cu(H2O)6]2+ (aq) + 2NH3 (aq) --> Cu(OH)2(H2O)4 (s) + 2NH4+ (aq) blue sol to blue ppt formed deprotonation acid-base rxn NH3 acts as BL base
47
hexa aqua iron (II) rxn w limited NH3
[Fe(H2O)6]2+ (aq) + 2NH3 (aq) --> Fe(OH)2(H2O)4 (s) + 2NH4+ (aq) green sol to green ppt formed deprotonation acid-base rxn NH3 acts as BL base
48
hexa aqua iron (III) rxn w limited NH3
[Fe(H2O)6]3+ (aq) + 3NH3 (aq) --> Fe(OH)3(H2O)3 (s) + 3NH4+ (aq) pale violet sol to brown ppt deprotonation acid-base rxn NH3 acts as BL base
49
hexa aqua Al 3+ rxn w limited NH3
[Al(H2O)6]3+ (aq) + 3NH3 (aq) --> Al(OH)3(H2O)3 (s) + 3NH4+ (aq) colourless sol to white ppt deprotonation acid-base rxn NH3 acts as BL base
50
Cu(OH)2(H2O)4 rxn w excess NH3 (aq)
Cu(OH)2(H2O)4 (s) + 4 NH3 (aq) --> [Cu(NH3)4(H2O)2]2+ (aq) + 2H2O (l) + 2OH- (aq) blue sol to deep blue sol incomplete substitution NH3 acts as lewis base (e- pair donor)
51
hexa aqua Fe2+, Fe3+, Al3+ rxn w excess NH3
no further rxn
52
hexa aqua Cu 2+ rxn w carbonate ions CO3 2- (from Na2CO3) type of rxn
[Cu(H2O)6]2+ (aq) + CO3 2- (aq) --> CuCO3 (s) + 6H2O (l) blue sol to blue/green ppt precipitation rxn insoluble metal carbonate
53
hexa aqua Fe 2+ rxn w carbonate ions CO3 2- (from Na2CO3) type of rxn
[Fe(H2O)6]2+ (aq) + CO3 2- (aq) --> FeCO3 (s) + 6H2O (l) green sol to green ppt precipitation rxn insoluble metal carbonate
54
hexa aqua Fe 3+ rxn w carbonate ions CO3 2- (from Na2CO3) type of rxn
2[Fe(H2O)6]3+ (aq) + 3CO3 2- (aq) --> Fe(H2O)3(OH)3 (s) + 3CO2 (g) + 3H2O (l) violet sol to brown ppt + bubbles of gas CO2 acidity rxn hydrated metal hydroxide
55
hexa aqua Al 3+ rxn w carbonate ions CO3 2- (from Na2CO3) type of rxn
2[Al(H2O)6]3+ (aq) + 3CO3 2- (aq) --> Al(H2O)3(OH)3 (s) + 3CO2 (g) + 3H2O (l) colourless sol to white ppt + bubbles of gas CO2 acidity rxn hydrated metal hydroxide
56
gen eqn hydrolysis rxns for 2+ ion
[M(H2O)6]2+ + H2O rev arrow [M(H2O)5(OH)]+ + H3O+ weak acidic sol
57
gen eqn hydrolysis rxn for 3+ ion
[M(H2O)6]3+ + H2O rev arrow [M(H2O)5(OH)]2+ + H3O+
58
[Fe(H2O)4(OH)2] in air
[Fe(H2O)3(OH)3] colour darkens due to oxidation
59
[Fe(H2O)4(OH)2] rxn w excess acid
basic metal hydroxide [Fe(H2O)6]2+ green ppt to green sol
60
[Fe(H2O)3(OH)3] rxn w excess acid
basic metal hydroxide [Fe(H2O)6]3+ brown ppt to orange sol
61
[Cu(H2O)4(OH)2] rxn w excess acid
basic metal hydroxide [Cu(H2O)6]2+ blue ppt to blue sol
62
Explain why an aq sol containing [Fe(H2O)6]3+ has lower pH than an aq sol containing [Fe(H2O)6]2+
Fe3+ smaller than Fe2+ has a higher charge-density ratio is more polarising so more O-H bonds in water ligand break more H+ released

AQA A-LEVEL CHEMISTRY (4 decks)

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