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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

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
Q

ox half eqn of aldehyde (ethanal) to ___

A

carboxylic acid (ethanoic acid)

CH3CHO + H2O –> CH3COOH + 2H+ + 2e-

26
Q

redox eqn: MnO4- in acidic conditions - which acid is used

A

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
Q

Fe2+ with MnO4- redox titration overall eqn

A

5Fe2+ + MnO4- + 8H+ –> 5Fe3+ + Mn2+ + 4H2O

purple to colourless

28
Q

if Fe (0) used to redox titration w MnO4-

A

react Fe (0) w H2SO4 to oxidise it to Fe2+

29
Q

if Fe (3+) used to redox titration w MnO4-

A

react Fe (3+) w Zn to reduce it to Fe2+

30
Q

C2O4 2- (forms 2 CO2) with MnO4- (forms Mn 2+) redox titration overall eqn

A

2MnO4- + 16H+ + 5C2O4 2- –> 10CO2 + 2Mn 2+ + 8H2O

31
Q

V2O5 (heterogeneous catalyst) in contact process eqns

A

overall: 2SO2 + O2 –> 2SO3
step 1: SO2 + V2O5 –> SO3 + V2O4
step 2: 2V2O4 + O2 –> 2V2O5

32
Q

I- and S2O8 2- catalysed by Fe2+ (homogeneous catalyst) rxn eqns

why is rxn slow before cat added

why Zn2+ dont catalyse rxn

A

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
Q

ox eqn C2O4 2- to 2 CO2

A

C2O4 2- –> 2CO2 + 2e-

34
Q

[Fe(H2O)6]2+ colour

35
Q

[Cu(H2O)6]2+ colour

36
Q

[Al(H2O)6]3+ colour

A

colourless sol

37
Q

[Fe(H2O)6]3+ (s) colour

A

pale violet seen in solid hydrated
salts that contain these complexes

38
Q

[Fe(H2O)6]3+ in soloution colour

A

yellow brown sol due to hydrolysis

39
Q

hexa aqua cu 2+ rxn w limited OH- (from NaOH)

Type of rxn
OH acts as what and why

A

[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
Q

hexa aqua iron (II) rxn w limited OH- (from NaOH)

A

[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
Q

hexa aqua iron (III) rxn w limited OH- (from NaOH)

A

[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
Q

hexa aqua Al 3+ rxn w limited OH- (from NaOH)

A

[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
Q

Al(H2O)3(OH)3 rxn w excess OH- alkali (from NaOH)

A

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
Q

Al(H2O)3(OH)3 rxn w excess acid

A

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
Q

hexa aqua Cu2+, Fe2+, Fe3+ rxn w excess OH- (from NaOH)

A

no further rxn

46
Q

hexa aqua cu 2+ rxn w limited NH3

A

[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
Q

hexa aqua iron (II) rxn w limited NH3

A

[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
Q

hexa aqua iron (III) rxn w limited NH3

A

[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
Q

hexa aqua Al 3+ rxn w limited NH3

A

[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
Q

Cu(OH)2(H2O)4 rxn w excess NH3 (aq)

A

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
Q

hexa aqua Fe2+, Fe3+, Al3+ rxn w excess NH3

A

no further rxn

52
Q

hexa aqua Cu 2+ rxn w carbonate ions CO3 2- (from Na2CO3)

type of rxn

A

[Cu(H2O)6]2+ (aq) + CO3 2- (aq) –> CuCO3 (s) + 6H2O (l)
blue sol to blue/green ppt

precipitation rxn
insoluble metal carbonate

53
Q

hexa aqua Fe 2+ rxn w carbonate ions CO3 2- (from Na2CO3)

type of rxn

A

[Fe(H2O)6]2+ (aq) + CO3 2- (aq) –> FeCO3 (s) + 6H2O (l)
green sol to green ppt

precipitation rxn
insoluble metal carbonate

54
Q

hexa aqua Fe 3+ rxn w carbonate ions CO3 2- (from Na2CO3)

type of rxn

A

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
Q

hexa aqua Al 3+ rxn w carbonate ions CO3 2- (from Na2CO3)

type of rxn

A

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
Q

gen eqn hydrolysis rxns for 2+ ion

A

[M(H2O)6]2+ + H2O rev arrow [M(H2O)5(OH)]+ + H3O+

weak acidic sol

57
Q

gen eqn hydrolysis rxn for 3+ ion

A

[M(H2O)6]3+ + H2O rev arrow [M(H2O)5(OH)]2+ + H3O+

58
Q

[Fe(H2O)4(OH)2] in air

A

[Fe(H2O)3(OH)3] colour darkens due to oxidation

59
Q

[Fe(H2O)4(OH)2] rxn w excess acid

A

basic metal hydroxide
[Fe(H2O)6]2+

green ppt to green sol

60
Q

[Fe(H2O)3(OH)3] rxn w excess acid

A

basic metal hydroxide
[Fe(H2O)6]3+

brown ppt to orange sol

61
Q

[Cu(H2O)4(OH)2] rxn w excess acid

A

basic metal hydroxide
[Cu(H2O)6]2+

blue ppt to blue sol

62
Q

Explain why an aq sol containing [Fe(H2O)6]3+ has lower pH than an aq sol containing [Fe(H2O)6]2+

A

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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