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chemistry year 13 > 5.3 > Flashcards

5.3 Flashcards

(85 cards)

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1
Q

which is higher energy 4s or 3d
which fills first and which loses first

A

4s

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2
Q

examples of d block elements that aren’t transition?

A

scandium, only forms 3+ ion with all d orbitals empty
zinc, only forms 2+ ion with all d orbitals full

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3
Q

what’s a transition metal

A

d-block elements that form one or more stable ions with a partially filled d-subshell

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4
Q

properties of transition metals

A

high densities, melting and boiling points
form coloured compounds
catalytic properties

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5
Q

why are transition metals good catalysts

A

partially filled d orbitals can be used to form bonds with adsorbed reactants to help reactions to take place more easily

and they can change oxidation number so can form intermediates as part of the reaction pathway

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6
Q

what catalyst is used in the decomposition of H2O2

A

manganese dioxide

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7
Q

what catalyst is used in the reaction of zinc with acids

A

Cu2+

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8
Q

what is a ligand

A

a molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond

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9
Q

what’s a complex ion

A

a transition metal ion bonded to one or more ligands by coordinate bonds

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10
Q

what is coordination number

A

the total number of coordinate bonds formed between a central metal ion and its ligands

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11
Q

what’s a monodentate ligand

A

ligands that form one coordinate bond

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12
Q

examples of monodentate ligands

A

Cl-, NH3, H2O, OH-, CN-

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13
Q

what’s a bidentate ligand

A

ligand that forms two coordinate bonds

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14
Q

examples of bidentate ligands

A

H2N-CH2-CH2-NH2, C2O4^2-

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15
Q

what is a multidentate ligand

A

ligand that forms several coordinate bonds

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16
Q

eg of multidentate ligand

A

EDTA - hexadentate

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17
Q

example of a complex with coordination number 6
bond angle?

A

[Cu(H2O)6]^2+
90° (octahedral)

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18
Q

example of a complex with coordination number 4
tetrahedral
square planar
bond angle?

A

tetrahedral: [CuCl4]^2-
109.5°
square planar: [Pt(NH3)2Cl2]
90°

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19
Q

example of a complex with coordination number 2
bond angle?

A

[Ag(NH3)2]^+
180° (linear)

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20
Q

what to remember when drawing complexes

A

draw bonds from the place with the lone pair (that is actually bonding)
draw 3d unless told not to
remember [ ] and charge (it’s an ion)

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21
Q

in what scenarios are octahedral complexes cis/trans

A

4 monodentate A ligands and 2 monodentate B ligands

or

2 bidentate A ligands and 2 monodentate B ligands

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22
Q

when are octohedral complexes cis or trans

A

cis when they’re within 90° of eachother (next to eachother)

trans when they’re opposite (180° away)

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23
Q

what scenario can a complex with coordinate number 4 have cistrans isomerism

A

only square planar (2 monodentate A and 2 monodentate B)

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24
Q

how is cisplatin used to treat cancer

A

binds to dna of cell
prevents cell division and spread of cancer

but causes sickness, hair loss, fatigue

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25
cis platin formula
[Pt(NH3)2 Cl2]
26
when can optical isomerism happen in complexes
3 bidentate A ligands 2 bidentate A ligands and 2 monodentate B ligands 1 hexadentate ligand
27
what is the chelate effect
in ligand sub reactions, positive entropy change is favourable, as it means a more stable complex is formed, so it is better to have more moles on the right of the reaction than the left (subbing monodentate with multidentate)
28
what is a ligand substitution reaction
a reaction in which one ligand in a complex ion is replaced by another ligand
29
why would a ligand get substituted by another
if the new ligand is less electronegative it will replace the old one because it finds it easier to donate a pair of electrons so forms stronger coordinate bonds
30
why does the chelate affect happen in terms of thermodynamics
the greater the increase in entropy, the more negative the free energy change is, making the reaction more feasible
31
what’s the enthalpy change for ligand sub reactions why
almost 0 because the bonds being broken and made are very similar
32
how is haemoglobin bonded
Fe^2+ ion bonded with 4 coordinate bonds to the N atoms in the haem group coordinate bond with protein globin coordinate bond with O2
33
why is carbon monoxide an issue in terms with haemoglobin
oxygen bonds to the Fe^2+ ion are reversible CO can bond in the same place as oxygen, but this substitution isn’t reversible so the haemoglobin can’t carry oxygen round the body to the organs
34
how do transition element compounds appear coloured
they absorb some wavelengths of light but the remaining wavelengths are reflected and transmitted to the human
35
why can transition elements form coloured compounds why are some compounds colourless
the electrons in the partially filled d subshell are excited when there are no available electrons to excite light can’t be absorbed so is colourless
36
what shape are complexes with just Cl^- ligands
tetrahedral (because Cl is quite big)
37
how to change Fe2+ to Fe3+ colour change
will readily happen in oxygen as iron is more stable in +3 oxidation state green to brown
38
how do you approach redox titrations/ what do you need to find
approach as a normal titration question, but instead of acids and bases it’s oxidised and reduced species
39
what can manganate be used to oxidise
Fe2+ to Fe3+
40
manganate colour change when used in redox titration
MnO4- —> Mn2+ purple —> very pale pink +7 —> +2
41
what are the conditions for iron manganate redox titrations and why
acidic because it is in the presence of H+ ions from the half equations
42
how do you know end point has been reached in iron manganate redox titrations
when excess MnO4- ions are present (all Fe2+ had reacted) so faint pink colour appears
43
what can iodine be used to oxidise in a redox titration
thiosulphate ions S2O3^2-
44
what is iodines colour change when used in redox titrations
I2 —> I- blue black —> colourless 0 —> 1
45
what conditions do iodine thiosulphate redox titrations need and why
need to be in the presence of starch for iodines colour change to occur
46
what is the end point of iodine thiosulphate redox titrations
when all the blue black colour disappears so all the iodine has oxidised thé thiosulphate ions
47
what’s the overall equation between thiosulphate ions and iodine
2S2O3^2- + I2 —> S4O6^2- + 2I-
48
what can dichromate ions be used to oxidise
Fe2+ to Fe3+
49
what do dichromate ions reduce to when tut rated with Fe2+
Cr3+
50
how can you recognise endpoint with dichromate iron redox titrations
redox indicator used to detect endpoint as the colour change is very subtle
51
example of a redox indicator endpoint colour
diphenylamine sulfonate violet-blue endpoint
52
how to estimate amount of Cu2+ ions
add aqueous iodide ions to make a solution containing iodine and Cu+ ions titrate against thiosulphate ions iodine will react into iodide and the brown colour will disappear add starch to show the iodine, endpoint is when the blue black colour disappears
53
what order should you do the negative ion tests in and why
carbonate —> sulphate —> halide because they can give false positives
54
carbonate test
add dilute strong acid collect gas bubble through limewater cloudy=carbonate
55
ionic equation for the carbonate test
CO3^2- (aq) + 2H^+ (aq) —> H2O (l) + CO2 (g)
56
sulphate test
add dilute acid and barium chloride white precipitate=sulphate
57
sulphate test ionic equation
Ba^2+ (aq) + SO4^2- (aq) —> BaSO4 (s)
58
halide test
dissolve in water acidify with dilute nitric acid add silver nitrate solution white/cream/yellow precipitate= chloride/bromide/iodide
59
how do you confirm which halogen it is in halide test
dissolves in dilute ammonia=chloride dissolves in conc ammonia=bromide doesn’t dissolve in ammonia= iodide
60
halide test ionic equation
Ag^+ (aq) + X^- (aq) —> AgX (s)
61
ammonium ion test
add sodium hydroxide solution and GENTLY WARM. will stink if ammonia but test with damp red litmus paper and it will turn blue
62
ionic equation for ammonium test
NH4^+ (aq) + OH^- (aq) —> NH3 (aq) + H2O (l)
63
what is a d block element
and element where the highest occupied energy orbital is a d-orbital
64
steps to balance redox half equation
work out whcih element is oxidised or reduced and balance if needed to equal amounts work out oxidation state and add electrons to balance oxidation states (remember stoichiometry) balance charges with H+ add water molecules or balance all the rest
65
what order should you do negative ion tests in
carbonate sulphate halide
66
how can haemoglobin transport oxygen around the body
O2 coordinate bonds with the Fe2+ ion, travels around the body, and is then released or substituted off
67
general format for precipitation reactions with addition of OH- ions to 2+ and 3+ complexes
[ _ (H2O)6]* + *OH- —> _(H2O)6-*(OH)* + *H2O
68
general format for precipitation reactions with addition of NH3 to 2+ and 3+ complexes
[ _ (H2O)6]* + *NH3 —> _(H2O)6-*(OH)* + *NH4+
69
how do OH- and NH3 act in precipitation reactions
as a base, they accept protons from the H2O ligands
70
what are the 2+ ions we need to know
Cu2+ Fe2+ Mn2+
71
what are the 3+ ions we need to know
Fe3+ Cr3+
72
general colour change of Cu2+ from aq complex to solid precipitate in addition of 2OH-/NH3
blue solution blue precipitate
73
general colour change of Fe2+ from aq complex to solid precipitate in addition of 2OH-/NH3
green solution green precipitate
74
general colour change of Mn2+ from aq complex to solid precipitate in addition of 2OH-/NH3
pale pink solution pale brown precipitate
75
general colour change of Fe3+ from aq complex to solid precipitate in addition of 3OH-/NH3
yellow/brown solution brown precipitate
76
general colour change of Cr3+ from aq complex to solid precipitate in addition of 3OH-/NH3
violet solution green precipitate
77
what happens when you add excess ammonia to Cu2+ hydroxide precipitate colour change?
4NH3 react to kick out 2H2O and 2OH- to make [Cu(H2O)2(NH3)4]2+ blue precipitate to deep blue solution
78
what happens when you add excess ammonia to Cr3+ hydroxide precipitate colour change?
6 NH3 reacts to kick out 3H2O and 3OH- to make [Cr(NH3)6]3+ aq green precipitate to purple solution
79
trick to remember how the excess ammonia reactions work
for 2+, kicks out 2 OH- and 2 H2O for 3+, kicks out 3 OH- and 3 H2O
80
what reacts with excess OH- and how and colour change
3OH- reacts with Cr 3+ hydroxide precipitate to make [Cr(OH)6]3- and 3H2O green precipitate to green solution
81
reaction between [Cr(OH)6]3- and H2O2 what’s happening in reaction colour change
2[Cr(OH)6]3-(aq) + 3H2O2 —> 2CrO4^2-(aq) +2OH- + 8H2O the hydrogen peroxide reduces the chromium green solution to yellow solution
82
what happens when you add aqueous chloride ions to hexaaquacopper complex colour change molecule shale change
4 Cl- substitute and kick out 6H2O from blue solution octahedral complex to yellow solution tetrahedral complex
83
How to answer question: how does haemoglobin transport oxygen around the body and why is CO toxic
O2 forms coordinate bonds with Fe2+. O2 is replaced by CO2 when needed. CO forms stronger coordinate bonds than O2, so it replaces O2 so it can no longer be carried around the body
84
What colour is Cr2O7^2-
Orange (dichromate)
85
What should you mention when discussing redox systems
Half cell potential AND EQUILIBRIUM SHIFTING

chemistry year 13 (6 decks)

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