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physical chem and transition elements Flashcards

1
Q

what does enthalpy of formation mean?

A

the enthalpy change when 1 mole of a compound is formed from its element under standard conditions

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2
Q

what does ionisation enthalpy mean?

A

the amount of energy required to remove an electron from a gaseous atom of an element to from a gaseous ion under standard conditions

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3
Q

what does enthalpy change of atomisation mean?

A

the enthalpy change when 1 mole of gaseous atoms is formed from its element under standard conditions

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4
Q

what does bond enthalpy mean?

A

the amount of energy required to break 1 mole of a specific covalent bond in the gas phase

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5
Q

what does lattice energy mean?

A

the enthalpy change when 1 mole of ionic compound is formed from its gaseous ions under standard conditions

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6
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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7
Q

what does enthalpy change of solution mean?

A

the enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions

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8
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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9
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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10
Q

list the states in ascending order of entropy

A

solid, liquid, gas

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11
Q

what is the equation for change in entropy (S)

A

Σ S products - Σ S reactants

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12
Q

what is the Gibbs equation used to calculate?

A

if a reaction is feasible or not

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13
Q

what is the Gibbs equation?

A

ΔGꝋ = ΔHreactionꝋ - TΔSsystemꝋ

ΔGꝋ = ΣΔGproductsꝋ - ΣΔGreactantsꝋ

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14
Q

what does a negative ΔGꝋ value mean?

A

the reaction is feasible

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15
Q

what does a positive ΔGꝋ value mean?

A

the reaction is not feasible

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16
Q

in an exothermic reaction, what is the feasibility if ΔSsystemꝋ is positive?

A
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17
Q

in an exothermic reaction, what is the feasibility if ΔSsystemꝋ is negative?

A

first term neg, second pos
at high temps, TΔSsystemꝋ is large and pos so overcomes ΔH
at high temps pos ΔGꝋ
not feasible

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18
Q

what is ΔH in an exothermic reaction?

A

negative

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19
Q

what is ΔH in an endo reaction?

A

positive

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20
Q

in an endothermic reaction, what is the feasibility if ΔSsystemꝋ is negative?

A

both terms pos
pos ΔGꝋ
not feasible regardless of temp

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21
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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22
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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23
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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24
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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25
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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26
Q

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

A

can be oxidised to Cl by manganate (VII)

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27
Q

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

A

oxidising agent
may oxidise substances

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28
Q

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

A

weak acid
insufficient concentration of H+ ions

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29
Q

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

A

may oxidise substances

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30
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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31
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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32
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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33
Q

what does the position of equilibrium and electrode potential depend on?

A

temp
pressure of gases
conc of reagents

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34
Q

what conditions are used when comparing electrode potentials?

A

standard
ion conc of 1moldm-3
298K
100kPa

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35
Q

what is used to take standard electrode potential measurements?

A

high resistance voltmeter

so no current flows
and max pd achieved

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36
Q

what is a standard hydrogen electrode?

A

contains hydrogen gas in equilibrium with H+ ions of concentration 1moldm-3 at 100kPa and an inert platinum electrode
0.00V

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37
Q

what is standard electrode potential?

A

potential difference produced when a standard half cell is connected to a standard hydrogen cell under standard conditions

38
Q

which half cell is more likely to get reduced?

A

the more positive one

39
Q

which half cell is less likely to get reduced?

A

the more negative one

40
Q

what are the different types of half cells that can be connected to standard hydrogen electrodes?

A
41
Q

why is platinum wire used as an electrode?

A

inert

42
Q

what are the units of rate of reaction?

A

mol dm-3 s-1

43
Q

which step is the rate determining step?

A

the slowest step in the reaction

44
Q

what are transition elements?

A

elements w an incomplete d sub shell that can from at least 1 stable ion w an incomplete d sub shell

45
Q

what are the properties of transition elements?

A

forming coloured compounds
used as catalysts
forming complex ions
variable oxidation states

46
Q

test for CO3^2-

A

add dilute acid
effervescence
test gas w limewater
confirms its CO2

47
Q

test for SO4^2-

A

acidified BaCl2
white ppt of BaSO4

48
Q

test for halide ions

A

add acidified AgNO3
AgCl white ppt- dissolves in dilute ammonia
AgBr cream- dissolves in conc
AgI yellow- insoluble

49
Q

test for ammonium ions

A

add OH-
ammonia gas forms
which turns damp red litmus paper blue
confirming presence of NH4+ in og solution

50
Q

ligand

A

a molecule or ion that can donate an electron pair to a transition metal ion

51
Q

coordination number

A

the total number of dative covalent bonds formed between the central metal ion and its ligands

52
Q

complex ions

A

transition metal ion bonded to ligands by dative covalent bonds

53
Q

coordinate/ dative covalent bonds

A

sharing of a pair of electrons, with both electrons coming from the same atom

54
Q

monodentate ligand

A

ligand that is able to donate 1 pair of electrons to the central metal ion

55
Q

bidentate ligand

A

ligand that is able to donate 2 pairs of electrons to the central metal ion

56
Q

examples of monodentate ligands

A

H2O
OH-
NH3
CN-
Cl-

57
Q

examples of bidentate ligands

A

1,2- diaminoethane
ethandioate

58
Q

how many bonds in octahedral shape and what is the bond angle

A

6
90º

59
Q

how many bonds in tetrahedral shape and what is the bond angle

A

4
109.5º

60
Q

how many bonds in square planar shape and what is the bond angle

A

4
90º

61
Q

what are ligand substitution reactions?

A

when one ligand in a complex is replaced by another
to form a more stable complex
ligands can be partially or entirely substituted

62
Q

what is the Arrhenius equation?

A

ln(k) = (−Ea/R)(1/T)+ln(A)

63
Q

when do transition element complexes show cis stereoisomerism?

A

when 2 different ligands are next to each other

64
Q

when do transition element complexes show trans stereoisomerism?

A

when 2 different ligands are opposite to each other

65
Q

what shape transition element complexes show optical isomerism?

A

octahedral complexes with bidentate ligands

66
Q

what are optical isomers?

A

2 forms are non superimposable mirror images
no plane of symmetry
one image cannot be placed directly on top of the other

67
Q

how does cisplatin work to treat cancer?

A

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

68
Q

why is hair loss a side effect of cancer treatment?

A

cisplatin binds to other quickly replicating cells eg hair follicles

69
Q

how does haemoglobin transport oxygen?

A

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

70
Q

how does CO bond to haemoglobin?

A

CO is a better ligand than O2 so binds strongly and irreversibly to Fe(ll)
preventing O2 from being carried to cells

71
Q

what is anaemia?

A

lack of haemoglobin due to blood loss or iron deficiency

72
Q

[Cu(H2O)6]2+ (aq) colour

A

pale blue

73
Q

CoCl2.6H2O (s) plus water and excess HCl

A

CoCl4^2-
blue

74
Q

oxidation of Cr3+ with hot alkaline H2O2

A

CrO4^2-
yellow

75
Q

NaOH drowse to Fe3+(aq)

A

Fe(OH)3 (s)
orange brown ppt

76
Q

NH3 dropwise to Cu2+(aq)

A

Cu(OH)2(s)
pale blue ppt

77
Q

[Cr(H2O)6]3+

A

pale purple
Due to impurities, it is common for Cr(III) to appear green in solution

78
Q

[Mn(H2O)6]2+

A

pale pink

79
Q

MnO4–/Fe2+ > Mn2+/Fe3+

A

purple (MnO4–) to pale pink (Mn2+) (in titrations, so dilute that it is practically colourless)

80
Q

excess NH3 to Cu2+(aq)

A

[Cu(NH3)4(H2O)2]2+
dark blue

81
Q

NH3 dropwise to Cr 3+(aq)

A

Cr(OH)3(s)
dark green ppt

82
Q

NaOH dropwise to Mn2+(aq)

A

Mn(OH)2(s)
pale brown ppt

83
Q

excess HCl to Cu2+(aq)

A

CuCl4^2–
yellow

84
Q

excess NH3 to Cr2+(aq)

A

[Cr(NH3)6]3+
purple

85
Q

[Fe(H2O)6]2+

A

pale green

86
Q

I–/Fe3+ > I2/Fe2+

A

orange brown (Fe3+) to brown (I2)

87
Q

reduction of Cu2+ with I–

A

white precpitate (CuI) and brown I2

88
Q

excess OH– to Cr(OH)3(s)

A

[Cr(OH)6]3–
dark green

89
Q

NaOH dropwise to Fe2+(aq)

A

Fe(OH)2(s)
dark green ppt

90
Q

Disproportionation of Cu+

A

brown solid (Cu) and blue solution (CuSO4)

91
Q

Cr2O7^2–

A

orange

92
Q

[Fe(H2O)6]3+

A

yellow

chem (5 decks)

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