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A-Level Chemistry > Inorganic Unit 2.6: Reactions of Ions in Aqueous Solution > Flashcards

Inorganic Unit 2.6: Reactions of Ions in Aqueous Solution Flashcards

1
Q

define metal aqua ions

A

central metal ion with 6 water ligands

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2
Q

when are metal aqua ions present?

A

when salts are crystallised from solution

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3
Q
A
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4
Q

define hydrolysis

A

loss of H+ from H2O ligands (O-H bond in H2O ligand breaks)
(‘spontaneous’)

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5
Q

define substitution

A

replacement of H2O by other ligands (metal-ligand bond breaks)
= ligand exchange

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6
Q

define redox

A

metal changes oxidation state (gain or loss of e-s)

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7
Q

what are the metal aqua ions of Cu2+, Fe2+, Fe3+ & Al3+ & their colours?

A

[Cu(H2O)6]2+ blue solution
[Fe(H2O)6]2+ green solution
[Fe(H2O)6]3+ purple solution (may look yellow-brown due to some [Fe(H2O)5(OH)]2+ formed by hydrolysis)
[Al(H2O)6]3+ colourless solution

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8
Q

what are the equations for hydrolysis of M2+ aqua ions?

A

see booklet
neutral complexes are solid

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9
Q

what are the equations for hydrolysis of M3+ aqua ions?

A

see booklet
neutral compounds are solid

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10
Q

how is the equilibrium of hydrolysis reactions shifted right & left?

A

right: add base/OH- to remove H+ = deprotonation

left: add acid H+

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11
Q

neutral complex ions

A

insoluble in water
solid ppts
known as metal(II) hydroxides or metal (III) hydroxides

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12
Q

describe the trend in acidity/pH of solutions of aqueous metal ions

A

as charge on metal in metal aqua ion increases, acidity increases so pH decreases

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13
Q

what are the main species in solution & in water?

A

in solution, metal aqua ions lose H+ from H2O ligands

in water, the main species present is [M(H2O)6]n+, but some hydrolysis happens so solution is acidic

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14
Q

explain the trend in pH of solutions of metal aqua ions

A

as the charge on metal aqua ion increases, the pH decreases

metal ion with higher charge
pulls e-s in co-ordinate bond more strongly
so e-s pulled more strongly towards the O
which weakens O-H bond
so O-H is easier to break
H+ released so increased [H+] in solution
so pH decreases

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15
Q

some metal hydroxides show amphoteric character

A

by dissolving in both acids & bases
e.g. hydroxides of Al3+

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16
Q

describe the reaction of metal aqua ions with bases

A

hydrolysis/deprotonation
the base removes H+ pushing the equilibria right
common bases: NH3, OH-, CO32-
forms insoluble, neutral complex ppt

adding XS base = ligand eXchange
insoluble complex reacts further

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17
Q

what are the observations & equations for the reaction of [Fe(H2O)6]2+ with dropwise NaOH & XS NaOH?

A

with dropwise OH-: green solution –> green ppt
[Fe(H2O)6]2+ (aq) + 2OH-(aq) –> Fe(H2O)4(OH)2 + 2H2O(l)

with XS OH-: nvc

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18
Q

what are the observations & equations for the reaction of [Cu(H2O)6]2+ with dropwise NaOH & XS NaOH?

A

with dropwise OH-: blue solution –> blue ppt
[Cu(H2O)6]2+(aq) + 2OH-(aq) –> Cu(H2O)4(OH)2 + 2H2O(l)

with XS OH-: nvc

19
Q

what are the observations & equations for the reaction of [Fe(H2O)6]3+ with dropwise NaOH & XS NaOH?

A

with dropwise OH-: pale violet solution –> brown ppt
[Fe(H2O)6]3+(aq) + 3OH-(aq) –> Fe(H2O)3(OH)3 + 2H2O(l)

with XS OH-: nvc

20
Q

what are the observations & equations for the reaction of [Al(H2O)6]3+ with dropwise NaOH & XS NaOH?

A

with dropwise OH-: colourless solution –> white ppt
[Al(H2O)6]3+(aq) + 3OH-(aq) –> Al(H2O)3(OH)3 + 3H2O(l)

with XS OH-: white ppt –> colourless solution
Al(H2O)3(OH)3 + OH-(aq) –> [Al(H2O)2(OH)4]-(aq) + H2O(l)

21
Q

what are the observations & equations for the reaction of [Fe(H2O)6]2+ with dropwise NH3 & XS NH3?

A

with dropwise NH3: green solution –> green ppt
[Fe(H2O)6]2+(aq) + 2NH3(aq) –> Fe(H2O)4(OH2) + 2NH4+(aq)

with XS NH3: nvc

22
Q

what are the observations & equations for the reaction of [Cu(H2O)6]2+ with dropwise NH3 & XS NH3?

A

with dropwise NH3: blue solution –> blue ppt
[Cu(H2O)6]2+(aq) + 2NH3(aq) –> Cu(H2O)4(OH)2 + 2NH4+(aq)

with XS NH3: blue ppt –> deep blue solution
Cu(H2O)4(OH)2 + 4NH3(aq) –> [Cu(H2O)2(NH3)4]2+(aq) + 2OH- + 2H2O

23
Q

what are the observations & equations for the reaction of [Fe(H2O)6]3+ with dropwise NH3 & XS NH3?

A

with dropwise NH3: pale purple solution –> brown ppt
[Fe(H2O)6]3+(aq) + 3NH3(aq) –> Fe(H2O)3(OH)3 + 3NH4+(aq)

with XS NH3: nvc

24
Q

what are the observations & equations for the reaction of [Al(H2O)6]3+ with dropwise NH3 & XS NH3?

A

with dropwise NH3: colourless solution –> white ppt
[Al(H2O)6]3+(aq) + 3NH3(aq) –> Al(H2O)3(OH)3 + 3NH4+(aq)

with XS NH3: nvc

25
Q

dropwise
XS

A

deprotonation/hydrolysis
ligand eXchange

26
Q

what is the observation & equation for the reaction of [Fe(H2O)6]2+ with dropwise Na2CO3?

A

green solution –> green ppt
[Fe(H2O)6]2+(aq) + CO32- –> FeCO3(s) + 6H2O
precipitation reaction, not deprotonation

27
Q

what is the observation & equation for the reaction of [Cu(H2O)6]2+ with dropwise Na2CO3?

A

blue solution –> blue-green ppt
[Cu(H2O)6]2+(aq) + CO32- –> CuCO3(s) + 6H2O
precipitation

28
Q

what is the observation & equation for the reaction of [Fe(H2O)6]3+ with dropwise Na2CO3?

A

pale purple solution –> brown ppt & effervescence
2[Fe(H2O)6]3+(aq) + 3CO32- –> 2Fe(H2O)3(OH)3 + 3CO2 + 3H2O
hydrolysis/deprotonation/acid-base reaction

29
Q

what is the observations & equation for the reaction of [Al(H2O)6]3+ with dropwise Na2CO3?

A

colourless solution –> white ppt & effervescence
2[Al(H2O)6]3+(aq) + 3CO32- –> 2Al(H2O)3(OH)3 + 3CO2 + 3H2O
hydrolysis/deprotonation/acid-base reaction

30
Q

summary of reactions of metal aqua ions & Na2CO3

A

metal(II) aqua ions react to form ppt of metal (II) carbonates by precipitation

metal(III) aqua ions react to form bubbles of CO2 gas & ppt of metal(III)hydroxides by hydrolysis

31
Q

why do metal(II) aqua ions & metal(III) aqua ions react differently with Na2CO3?

A

[M(H2O)6]3+ is acidic enough to react in an acid base-reaction with CO32- ions by hydrolysis, but [M(H2O)6]2+ is not acidic enough

32
Q

what are the observations & equations for the reaction of [Fe(H2O)4(OH)2] with XS acid & XS alkali?

A

with XS acid: green ppt –> green solution
[Fe(H2O)4(OH)2] + 2H+ –> [Fe(H2O)6]2+

with XS alkali: nvc

33
Q

what are the observations & equations for the reaction of [Cu(H2O)4(OH)2] with XS acid & XS alkali?

A

with XS acid: blue ppt –> blue solution
[Cu(H2O)4(OH)2] + 2H+ –> [Cu(H2O)6]2+

with XS alkali: nvc

34
Q

what are the observations & equations for the reaction of [Fe(H2O)3(OH)3] with XS acid & XS alkali?

A

with XS acid: brown ppt –> pale purple solution
[Fe(H2O)3(OH)3] + 3H+ –> [Cu(H2O)6]3+

with XS alkali: nvc

35
Q

what are the observations & equations for the reaction of [Al(H2O)3(OH)3] with XS acid & XS alkali?

A

with XS acid: white ppt –> colourless solution
[Al(H2O)3(OH)3] + 3H+ –> [Al(H2O)6]3+

with XS alkali: white ppt –> colourless solution
[Al(H2O)3(OH)3] + OH- –> [Cu(H2O)2(OH)4]- + H2O

36
Q

define & give examples of:
acidic hydroxide
amphoteric hydroxide
basic hydroxide

A

acidic hydroxide: hydroxide that only reacts with bases

amphoteric hydroxide: hydroxide that reacts with both acids & bases
e.g. [Al(H2O)3(OH)3]

basic hydroxide: hydroxide that only reacts with acids
e.g. [Fe(H2O)4(OH)2]
[Cu(H2O)4(OH)2]
[Fe(H2O)3(OH)3]

37
Q

what are the observations & equations for the reaction of [Fe(H2O)6]2+, [Cu(H2O)6]2+, [Fe(H2O)6]3+ & [Al(H2O)6]3+ with similar sized ligands e.g. XS NH3(aq)

A

[Fe(H2O)6]2+, [Fe(H2O)6]3+ & [Al(H2O)6]3+ same as for dropwise NH3

[Cu(H2O)6]2+: blue solution –> deep blue solution
[Cu(H2O)6]2+ + 4NH3 –> [Cu(H2O)2(OH)4]2+ + 4H2O ligand substitution

38
Q

what is the observation & equation for the reaction of [Fe(H2O)6]2+ with larger ligands e.g. conc. HCl to provide XS Cl-?

A

green solution –> yellow solution
[Fe(H2O)6]2+ + 4Cl- –> [FeCl4]2- + 6H2O

39
Q

what is the observation & equation for the reaction of [Cu(H2O)6]2+ with larger ligands e.g. conc. HCl to provide XS Cl-?

A

blue solution –> yellow solution (may appear green)
[Cu(H2O)6]2+ + 4Cl- –> [CuCl4]2- + 6H2O

40
Q

what is the observation & equation for the reaction of [Fe(H2O)6]3+ with larger ligands e.g. conc. HCl to provide XS Cl-?

A

pale purple solution –> yellow solution
[Fe(H2O)6]3+ + 4Cl- –> [FeCl4]- + 6H2O

41
Q

what is the observation & equation for the reaction of [Al(H2O)6]3+ with larger ligands e.g. conc. HCl to provide XS Cl-?

A

nvc/colourless solution –> colourless solution
[Al(H2O)6]3+ + 4Cl- –> [AlCl4]- + 6H2O

42
Q

summary of substitution reactions with larger ligands

A

metal aqua ions react with conc. HCl by substitution
all 6 H2O ligands are replaced by 4 Cl- ligands

43
Q

what is the cobalt species & its colour formed from substitution reactions with:
NaOH
XS NH3(aq)
Na2CO3(aq)
conc. HCl(aq)?

A

NaOH: Co(H2O)4(OH)2 blue ppt

XS NH3(aq): [Co(NH3)6]2+(aq) pale brown solution that darkens on exposure to air

Na2CO3(aq): CoCO3(s) purple ppt

conc. HCl(aq): [CoCl4]2-(aq) blue solution

A-Level Chemistry (21 decks)

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