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physical chem and transition elements Flashcards

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1
Q

what does lattice enthalpy mean?

A

Formation of 1 mol of ionic lattice from gaseous ions

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2
Q

what factors affect lattice enthalpy?

A

ionic radius
as it increases, attraction between ions decreases so lattice enthalpy becomes less exothermic and melting point decreases

ionic charge
as it increases, attraction between ions increases so lattice enthalpy becomes more exothermic and melting point increases

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3
Q

what does standard enthalpy change of hydration mean?

A

when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions

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4
Q

what does the entropy (S) of a given system mean?

A

the number of possible arrangements of the particles and energy in a given system

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5
Q

list the states in ascending order of entropy

A

solid, liquid, gas

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6
Q

what is the equation for change in entropy (S)

A

Σ S products - Σ S reactants

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7
Q

what is the Gibbs equation used to calculate?

A

if a reaction is feasible or not

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8
Q

what is the Gibbs equation?

A

ΔGꝋ = ΔHreactionꝋ - TΔSsystemꝋ

ΔGꝋ = ΣΔGproductsꝋ - ΣΔGreactantsꝋ

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9
Q

what does a negative ΔGꝋ value mean?

A

the reaction is feasible

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10
Q

what does a positive ΔGꝋ value mean?

A

the reaction is not feasible

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11
Q

what is ΔH in an exothermic reaction?

A

negative

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12
Q

what is ΔH in an endo reaction?

A

positive

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13
Q

what are the limitations of using ΔG?

A

can only be used under standard conditions
doesn’t take into account rate of reaction
some reactions are feasible but not kinetically feasible cos too slow

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14
Q

what is an oxidising agent?

A

oxidise another atom/ ion by causing it to lose electrons
gets reduced- gains electrons
so oxidation number decreases

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15
Q

what is a reducing agent?

A

reduces another atom/ ion by causing it to gain electrons
gets oxidised- loses electrons
so oxidation number increases

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16
Q

explain potassium manganate (VII) titrations

A

manganate(VII) is oxidising agent
reduced to Mn2+
iron is reducing agent
oxidised to Fe3+
reaction mixture must be acidified to excess dilute sulphuric acid added to Fe3+ before reaction

potassium permanganate starts purple
Mn2+ is pale pink but appears colourless cos of low conc
when all Fe2+ reacted with Mn7+, pale pink solution due to excess Mn7+

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17
Q

why is dilute sulphuric acid suitable for potassium manganate (VII) titrations?

A

does not oxidise under the conditions
does not react with manganate (VII)

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18
Q

why is HCl not suitable for potassium manganate (VII) titrations?

A

can be oxidised to Cl by manganate (VII)

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19
Q

why is nitric acid not suitable for potassium manganate (VII) titrations?

A

oxidising agent
may oxidise substances

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20
Q

why is ethanoic acid not suitable for potassium manganate (VII) titrations?

A

weak acid
insufficient concentration of H+ ions

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21
Q

why is conc sulphuric acid not suitable for potassium manganate (VII) titrations?

A

may oxidise substances

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22
Q

explain iodine thiosulfate titrations

A

light brown/ yellow of iodine turns paler when converted to colourless iodide ions
when solution is a straw colour, starch is added
turns blue/black until all iodine reacts, then colour disappears

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23
Q

what can iodine thiosulfate titrations be used for determining?

A

amount of chlorate(I) in bleach
amount of Cu2+ in copper(II) compounds
copper content of alloys

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24
Q

what can potassium manganate titrations be used for determining?

A

percentage purity of iron supplements
formula of a sample of hydrated ethanedioic acid

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25
what does the position of equilibrium and electrode potential depend on?
temp pressure of gases conc of reagents
26
what conditions are used when comparing electrode potentials?
standard ion conc of 1moldm-3 298K 100kPa
27
what is used to take standard electrode potential measurements?
high resistance voltmeter so no current flows and max pd achieved
28
what is a standard hydrogen electrode?
contains hydrogen gas in equilibrium with H+ ions of concentration 1moldm-3 at 100kPa and an inert platinum electrode 0.00V
29
what is standard electrode potential?
potential difference produced when a standard half cell is connected to a standard hydrogen cell under standard conditions
30
which half cell is more likely to get reduced?
the more positive one
31
which half cell is less likely to get reduced?
the more negative one
32
why is platinum wire used as an electrode?
inert
33
what are the units of rate of reaction?
mol dm-3 s-1
34
which step is the rate determining step?
the slowest step in the reaction
35
what are transition elements?
elements w an incomplete d sub shell that can from at least 1 stable ion w an incomplete d sub shell
36
what are the properties of transition elements?
forming coloured compounds used as catalysts forming complex ions variable oxidation states
37
test for CO3^2-
add dilute acid effervescence test gas w limewater confirms its CO2
38
test for SO4^2-
acidified BaCl2 white ppt of BaSO4
39
test for halide ions
add acidified AgNO3 AgCl white ppt- dissolves in dilute ammonia AgBr cream- dissolves in conc AgI yellow- insoluble
40
test for ammonium ions
add OH- ammonia gas forms which turns damp red litmus paper blue confirming presence of NH4+ in og solution
41
ligand
a molecule or ion that can donate an electron pair to a transition metal ion
42
coordination number
the total number of dative covalent bonds formed between the central metal ion and its ligands
43
complex ions
transition metal ion bonded to ligands by dative covalent bonds
44
coordinate/ dative covalent bonds
sharing of a pair of electrons, with both electrons coming from the same atom
45
monodentate ligand
ligand that is able to donate 1 pair of electrons to the central metal ion
46
bidentate ligand
ligand that is able to donate 2 pairs of electrons to the central metal ion
47
examples of monodentate ligands
H2O OH- NH3 CN- Cl-
48
examples of bidentate ligands
1,2- diaminoethane ethandioate
49
how many bonds in octahedral shape and what is the bond angle
6 90º
50
how many bonds in tetrahedral shape and what is the bond angle
4 109.5º
51
how many bonds in square planar shape and what is the bond angle
4 90º
52
what are ligand substitution reactions?
when one ligand in a complex is replaced by another to form a more stable complex ligands can be partially or entirely substituted
53
when do transition element complexes show cis stereoisomerism?
when 2 different ligands are next to each other
54
when do transition element complexes show trans stereoisomerism?
when 2 different ligands are opposite to each other
55
what shape transition element complexes show optical isomerism?
octahedral complexes with bidentate ligands
56
what are optical isomers?
2 forms are non superimposable mirror images no plane of symmetry one image cannot be placed directly on top of the other
57
how does cisplatin work to treat cancer?
passes thru cell membrane and undergoes ligand exchange where cl is replaced by water N is a better ligand than water so forms dative covalent bonds w cisplatin cisplatin distorts shape of DNA and prevents it from replicating
58
why is hair loss a side effect of cancer treatment?
cisplatin binds to other quickly replicating cells eg hair follicles
59
how does haemoglobin transport oxygen?
haem molecule is a complex w a central Fe(ll) O2 form a dative covalent bond w Fe(ll) which enables O2 to be transported around body in blood O2 bond weakly to Fe(ll) weak bond allows them to break off easily and be transported into cells
60
how does CO bond to haemoglobin?
CO is a better ligand than O2 so binds strongly and irreversibly to Fe(ll) preventing O2 from being carried to cells
61
what is anaemia?
lack of haemoglobin due to blood loss or iron deficiency
62
units for Delta G
kJmol-1 or Jmol-1
63
is enthalpy change of formation endo or exo
exo
64
is enthalpy change of atomisation endo or exo
endo
65
is 1st e- affinity endo or exo
exo
66
is 2nd e- affinity endo or exo
endo
67
why is 2nd e- affinity endo
energy needed to add an e- onto a neg ion repulsion between e- and neg ion
68
factors that effect enthalpy change of hydration
charge: larger charge, larger enthalpy change of hydration size: smaller size, larger enthalpy change of hydration
69
thing to remember when calculating things from born haber cycles
go w arrow: keep sign same go against arrow: change sign
70
enthalpy change of solution equation
lattice enthalpy + enthalpy change of hydration
71
how to find temp at which feasibility changes
delta H / delta S
72
what elements are d block but not transition elements
Sc Zn
73
charge of bidentate ligand 1,2- diaminoethane
neutral
74
charge of bidentate ligand ethanedioate
2-
75
what shape do complexes w coordination number 6 always make
octahedral
76
what shape do complexes w coordination number 4 make
tetrahedral square planar
77
How to calculate mole fraction
Equilibrium moles of gas / Total moles
78
How to calculate partial pressure
Mole fraction x total pressure
79
What is the position of equilibrium if Kc = 1
Half way between reactants and products
80
What is the position of equilibrium if Kc > 1
Right More products at equilibrium
81
What is the position of equilibrium if Kc < 1
Left More reactants at equilibrium
82
What condition change affects Kc and Kp
Only temperature
83
What is the effect on Kc and Kp of increasing the temperature for a reaction which is forward exothermic
Shifts equilibrium to the left Kc and Kp decrease
84
What is the effect on Kc and Kp of increasing the temperature for a reaction which is forward endothermic
Shifts equilibrium to right Kc and Kp both increase
85
What is a bronsted acid
Species that can donate a proton
86
What is a brønsted base
Species that can accept a proton
87
What are conjugate acid-base pairs
2 species that are different from each other by an H+ ion
88
What is a monobasic acid
Contains 1 ionisable H atom
89
What is a bronsted acid
Proton donor
90
Monobasic acid examples
HCN HCl HNO3
91
Dibasic acid example
H2SO4
92
Tribasic acid example
H3PO4
93
What is a weak acid
Parcial dissociates in aqueos solution
94
Weak acid example
Ethanoic
95
Where is the position of equilibrium for weak acids
Left more HA molecules than H+ and A-
96
What is the acid dissociation constant ka
[H+][A-] / [HA]
97
Acid dissociation constant ka units
mol dm -3
98
What does a higher ka value mean
More dissociated, stronger acid
99
pH equation
-log [H+]
100
H+ ion concentration equation
10 ^ -pH
101
Assumption made when using ka
[H+] = [A-] at equilibrium Initial [HA] = equilibrium [HA]
102
what are buffers
solutions that resist changes in their pH when small amounts of acids or bases are added
103
what does a buffer solution consist of
a weak acid and a salt of the weak acid or excess of a weak acid and a strong alkali
104
equation for calculating [H+] in buffers
[H+] = Ka x [acid]/ [salt]
105
what acts as a buffer in blood
HCO3- CO2 + H2O > H+ + HCO3-
106
what should the pH of blood be
7.35 - 7.45
107
what is the equivalence point
point where acid has completely reacted w the base
108
what is the equivalence volume
volume of base required to completely react w acid
109
Uses of buffers
Shampoo, household cleaning products
110
% dissociation equation
[H+] / X 100 [acid]
111
what is an acid- base indicator
weak acid that dissociates to give an anion of a diff colour
112
what does the colour of an indicator depend on
ratio of weak acid to its conjugate base
113
what is the ratio in indicators of weak acid to conjugate base, at the endpoint of a titration
balanced
114
what is the pKa of an indicator equal to
pH of its endpoint
115
what makes an indicator appropriate to use for a titration
if its pH range falls within the rapid pH change of the titration
116
Why is Zn not a transition metal?
Zn can only form a +2 ion. In this ion the Zn2+ has a complete d orbital and so does not meet the criteria of having an incomplete d orbital in one of its ions.
117
Why is Sc not a transition metal?
Sc can only form a +3 ion. In this ion the Sc3+ has an empty d orbital and so does not meet the criteria of having an incomplete d orbital in one of its ions.
118
what transition metal complex shapes show cis- trans isomerism
octahedral square planar
119
what atoms are bonded to Pt in platin
Cl NH3
120
is enthalpy change of combustion exo or endo
exo
121
how to find enthalpy change of combustion from enthalpy changes of formation
products - reactants
122
is lattice enthalpy endo or exo
exo
123
do H+ ions exist on their own in water
no form hydronium ions H3+O
124
how to calibrate a pH meter
wash the probe with distilled water
125
what indicator is suitable for a weak acid weak base titration
No indicator is suitable for a weak acid/weak base titration. use pH meter
126
Practical examples of catalytic behaviour of transition elements
Cu2+ for reaction of Zn with acids MnO2 for decomposition of H2O2
127
where is the + charge on H3O+
on the oxygen
128
when an electrode potential is more negative, which way does equilibrium shift
left
129
Enthalpy change of solution
Dissolving I mol of solute
130
Enthalpy change of hydration
Dissolving 1 mol of gaseous ions in water
131
equation to find k with half life
k = ln (2) / half life
132
is condensation exo or endo
exo
133
standard enthalpy change of atomisation of iodine equation
1⁄2 I2(s) > I(g)
134
are solids and liquids in heterogeneous Kc and Kp expressions
no omitted cos constant
135
Potassium permanganate colour change
colourless to pale pink
136
risks of Li based cells
toxic fires
137
hydrogen oxygen fuel cell equations
2H2 (g) + 4OH– (aq) → 4H2O (l) + 4e– O2 (g) + 2H2O + 4e– → 4OH– (aq)
138
fuel cells
use energy from the reaction of a fuel w oxygen to create a voltage fuel donates electrons at one electrode and oxygen gains electrons at the other electrode

chem (7 decks)

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