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Chemistry - Module 5 > 24 - transition elements > Flashcards

24 - transition elements Flashcards

1
Q

what is a d block element

A

element where highest energy electron is in the d subshell

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2
Q

what are some general properties of metals

A

metallic

high m.p / b.p

shiny

conduct electricity + heat

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3
Q

what are the exceptions to the redox rules

A

Cr

Cu

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4
Q

what is a transition metal

A

d block elements that form at least 1 ion with a partially filled d-orbital

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5
Q

which d block elements are not transition metals

A

scandium + zinc

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6
Q

why is scandium not a transition metal

atomic number - 21

A

does not form an ion with a partially filled d orbital - has an empty d orbital

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7
Q

why is zinc not a transition metal

atomic number - 30

A

does not form an ion with a partially filled d orbital - has a full d orbital

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8
Q

what are the properties specific to transition metals

A

form ions with variable oxidation states

forms coloured compounds

act as catalysts

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9
Q

what is the oxidation state that all transition metals have

A

+2

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10
Q

colour of potassium dichromate

A

bright orange

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11
Q

colour of Cobalt (II) chloride

A

pink purple

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12
Q

colour of Cr04

A

yellow

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13
Q

how do transition elements form coloured compounds

A

linked to partially filled d orbitals

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14
Q

what happens if you dissolve a coloured compound

A

make coloured solutions

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15
Q

benefits + risks of using transition metals as catalysts

A

Benefits – reduces energy usage / lower costs

Risks – toxicity of many transition metals

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16
Q

examples of reactions where the transition metal is a heterogenous catalyst

A
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17
Q

examples of reactions where the transition metal is a heterogenous catalyst

A
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18
Q

what is a complex ion

A

Consists of a central metal ion with one or more molecules / charged ions (ligands) bound to it by dative covalent bonds

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19
Q

what are complex ions formed from

A

Formed by d-block elements

+ other elements – Aluminium

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20
Q

what is a ligand

A

Molecule / ion that donates a pair of electrons to a central metal atom by coordinate / dative covalent bonding

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21
Q

what is needed for something to be a ligand

A

Lone pairs needed

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22
Q

what are some neutral ligands

A

water / ammonia

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23
Q

what are some charged ligands

A

halide ions / CN- / hydroxide

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24
Q

how is a complex ion written out

A
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25
Q

what is the coordination number

A

Number of coordinate bonds made to the central metal atom

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26
Q

shape / bond angle / examples of coordination number 6

A

Octahedral

Bond angle – 90

Hexaaqua complexes

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27
Q

draw a 3D shape of a complex ion with a coordination number of 6

A
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28
Q

what are the shapes that arise from a coordination number of 4

A

tetrahedral and square planar

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29
Q

bond angle + example for tetrahedral

A

Bond angle – 109.5

Tetrachloro complexes

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30
Q

bond angle for square planar

A

90

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31
Q

which metals make square planar complexes over tetrahedral

A

tends to occur for transition metals with 8 d electrons

Platinum (II), palladium (II) and gold (III)

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32
Q

draw a tetrahedral complex

A
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33
Q

draw a square planar complex

A
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34
Q

what is a monodentate ligand

A

ligand that is able to donate one pair of electrons to a central metal atom

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35
Q

what is a bidentate ligand

A

able to donate 2 pairs of electrons to a central metal atom

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36
Q

what are 5 examples of monodentate ligands

A
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37
Q

examples of bidentate ligands

A
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38
Q

what complexes show cis-trans isomerism

A

4 coordinate + 6 coordinate complex ions with different monodentate / bidentate ligands

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39
Q

which complexes show both cis trans and optical isomerism

A

6 coordinate complexes with monodentate and bidentate ligands

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40
Q

what needs to be for a square planar complex to show cis trans isomerism

A

have no more than 2 identical ligands

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41
Q

cis square planar

A

two identical ligands are adjacent to eachother - 90 degrees apart

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42
Q

trans square planar

A

two identical ligands are opposite each other - 180 degrees apart

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43
Q

draw the cis + trans isomers of [Pd(NH3)2(Cl)2]

A
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44
Q

what needs to be for an octahedral monodentate complex to show cis trans isomerism

A

contain 4 of one type + 2 of another type of ligand

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45
Q

cis monodentate octahedral

A

two identical ligands are adjacent to each other - 90 degrees

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46
Q

trans monodentate octahedral

A

two identical ligands are opposite to each other - 180 degrees

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47
Q

draw the cis + trans isomers of [Co(NH3)4(Cl)2]+

A
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48
Q

what needs to be for an octahedral bidentate complex to show cis trans isomerism

A

contain 2 bidentate ligands + 2 identical monodentate ligands

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49
Q

cis bidentate octahedral

A

two identical monodentate ligands adjacent to each other - 90 degrees

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50
Q

trans bidentate octahedral

A

two identical monodentate ligands are opposite to each other - 180 degrees

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51
Q

draw cis + trans [Co(NH3CH2CH2NH2)2 (Cl)2]+

A
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52
Q

do square planar complexes show optical isomerism

A

no

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53
Q

do octahedral complexes show optical isomerism

A

yes

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54
Q

what needs to be for a octahedral complex to show optical isomerism

A

ONLY in cis isomers with 2 or more bidentate ligands

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55
Q

can trans octahedral show optical isomerism

A

no

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56
Q

can cis octahedral show optical isomerism

A

yes

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57
Q

draw the optical isomers of [Co(NH3CH2CH2NH2)2 (Cl)2]+

A

remember only cis

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58
Q

draw optical isomers of [Ni(NH3CH2CH2NH2)3]2+

A
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59
Q

what is ligand substitution

A

Where 1 ligand is exchanged for another

60
Q

what does ligand substitution normally cause

A

colour change

61
Q

what occurs when ligand exchange happens between two similar sized ligands

A

If ligands similar size – coordination number of complex ion or shape does not change

62
Q

what are some examples of similar sized ligands

A

H2O

NH3

63
Q

what colour is a solution of [Cr(H2O)6]3+

A

violet solution

64
Q

write out the reaction between [Cr(H2O)6]3+ and NH3

A
65
Q

describe the observations for the reaction between [Cr(H2O)6]3+ and NH3

A

colour change from a violet solution to a purple solution

66
Q

does the shape of the metal complex change when you react [Cr(H2O)6]3+ and NH3

A

no - both octahedral as they are similar sized ligands

67
Q

what colour is [Cr(NH3)6]3+

A

purple solution

68
Q

what colour is [Cr(H2O)5SO4]+

A

green solution

69
Q

write out the reaction between [Cr(H2O)5SO4]+ and NH3

A
70
Q

describe the observations for the reaction between [Cr(H2O)5SO4]+ and NH3

A

colour change from green to purple

71
Q

does the shape of the metal complex change when you react [Cr(H2O)5SO4]+ and NH3

A

no - both octahedral - as similar sized ligands

72
Q

what are the products in the reaction between [Cr(H2O)5SO4]+ and NH3

A
73
Q

does copper undergo ligand exchange

A

yes BUT only partial exchange

74
Q

what colour is [Cu(H2O)6]2+

A

pale blue solution

75
Q

write out the equation when [Cu(H2O)6]2+ reacts with ammonia

A
76
Q

draw [Cu(H2O)6]2+

A
77
Q

describe the observations for the reaction between [Cu(H2O)6]2+ and ammonia

A

pale blue to dark blue solution

78
Q

does the shape of the metal complex change when you react [Cu(H2O)6]2+ and ammonia

A

no - both octahedral as they are similar sized ligands

79
Q

what are the products in the reaction between [Cu(H2O)6]2+ and ammonia

A
80
Q

draw [Cu(NH3)4(H2O)2]2+

A
81
Q

what happens if a small uncharged swapped for large charged ligand (or vice versa)

A

change in shape + coordination number

82
Q

write out the reaction between [Cu(H2O)6]2+ and chloride ions

A
83
Q

describe the observations that occur when you react [Cu(H2O)6]2+ and chloride ions

A

pale blue to yellow

84
Q

does the shape of the metal complex change when you react [Cu(H2O)6]2+ and chloride ions

A

yes - because Cl- are smaller

85
Q

what is the shape change when you react [Cu(H2O)6]2+ and chloride ions

A

[Cu(H2O)6]2+ = tetrahedral

[Cu(Cl4)]2- = tetrahedral

86
Q

where do the chloride ions come from in the reaction between [Cu(H2O)6]2+ and chloride ions

A

concentrated HCl

87
Q

what are the products the reaction between [Cu(H2O)6]2+ and chloride ions

A
88
Q

draw both [Cu(H2O)6]2+ and [Cu(Cl4)]2-

A
89
Q

how does ammonia form hydroxide ions

A

NH3 + H2O ⇌ NH4+ + OH-

90
Q

Why does the solution of aqueous copper (II) ions reacting with chloride ions turn green as the reaction proceeds?

A

The yellow and blue solutions mixing gives a green colour.

91
Q

What is formed when chromium(III) potassium sulphate is dissolved in water?

what’s the formula and colour?

A

The complex ion [Cr(H2O)6]3+ is formed.

A pale purple solution.

92
Q

What is formed instead when only chromium(III) sulphate is dissolved in water?

what’s the formula and colour?

A

The complex ion [Cr(H2O)5SO4]+ is formed.

A green solution.

93
Q

what happens if ammonia / sodium hydroxide added to aqueous transition metal complexes dropwise

A

coloured precipitates of insoluble transition metal hydroxide forms

94
Q

what is a precipitation reaction

A

two aqueous solutions that contain ions react together to form an insoluble ionic solid

95
Q

are precipitation reactions reversible

A

yes

precipitates can be re-dissolved by adding acid

96
Q

when you add ammonia / sodium hydroxide to these metal complexes what happens first

A

it will initially form the metal hydroxide

97
Q

What colour is Fe2+

A

pale green solution

98
Q

what are the observations when you add dropwise ammonia / sodium hydroxide to Fe2+

A

pale green solution to a green ppt (turns orange on standing)

99
Q

what is the green ppt when you add dropwise ammonia / sodium hydroxide to Fe2+

A

Fe(OH)2

100
Q

write out the reaction between dropwise ammonia / sodium hydroxide and Fe2+

A
101
Q

why does Fe(OH)2 turn orange on standing

A

gets oxidised to Fe3+

102
Q

what colour is Fe3+

A

pale yellow solution

103
Q

what are the observations when you add dropwise ammonia / sodium hydroxide to Fe3+

A

pale yellow solution to orange brown ppt

104
Q

what is the orange brown ppt

A

Fe(OH)3

105
Q

write out the reaction between dropwise ammonia / sodium hydroxide and Fe2+

A
106
Q

describe the observations when you react [Cu(H2O)6]2+ with dropwise ammonia vs excess ammonia

A
107
Q

describe the observations when you react [Cr(H2O)6]3+ with dropwise ammonia vs excess ammonia

A
108
Q

describe the observations when you react [Cr(H2O)6]3+ with dropwise sodium hydroxide vs excess sodium hydroxide

A
109
Q

Describe the precipitation reaction of Fe2+ with OH and what is the equation?

A

Fe2+ + 2OH- = Fe(OH)2 (s)

pale green solution to green precipitate

110
Q

Describe the precipitation reaction of Fe3+ with OH and what is the equation?

A

Fe3+ + 3OH- = Fe(OH)3 (s)

pale yellow to orange-brown precipitate

111
Q

Describe the precipitation reaction of Mn2+ with OH and what is the equation?

A

Mn2+ + 2OH- = Mn (OH)2 (s)

pale pink solution to light brown precipitate

112
Q

Describe the precipitation reaction of Cr3+ with OH and what is the equation?

A

Cr3+ (aq) + 3OH- (aq) = Cr(OH)3 (s)

violet solution to green precipitate

113
Q

Describe the precipitation reaction of Cu2+ with NaOH and what is the equation?

A

Cu2+(aq)+2NaOH(aq)→ Cu(OH)2(s)+2Na+(aq)

pale blue solution to a blue precipitate of copper(II) hydroxide.

114
Q

How do Cr3+ react with an excess of aqueous NaOH?

A

the hydroxide of Cr 3+ does dissolve in excess NaOH

Cr3+ + NaOH (aq)= Cr(OH)3 (s)

excess NaOH=[Cr (OH)6] 3-

115
Q

Cu2+

appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH

A
116
Q

Fe2+

appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH

A
117
Q

Fe3+

appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH

A
118
Q

Mn2+

appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH

A
119
Q

Cr3+

appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH

A
120
Q

what is haemoglobin

A

A metalloprotein

121
Q

what is the structure of haemoglobin

A

Central Fe2+ metal ion

Multidentate haem ring = 4 nitrogen’s, forming 4 dative covalent bonds (in square planar configuration)

Also forms a dative bond with the protein globin

Finally, dative bond with O2 or H2O (ligands)

Coordination number 6, octahedral overall

122
Q

how is oxyhaemoglobin

A
  • Binds reversibly with oxygen via ligand exchange
123
Q

how is the dative bond between oxygen and Fe2+ advantageous

A

as it releases O2 when needed

124
Q

why is carbon monoxide dangerous

A

Carbon monoxide has a lone pair of electrons on its carbon – can act as a ligand

much stronger dative bond forms between CO and Fe2+ in the haem group than O2

Any CO breathed in, will permenantly replace O2, ligand exchange

Forms carboxyhaemoglobin

125
Q

write out both equations of haemoglobin + oxygen / carbon monoxide

A

Haemoglobin + oxygen ⇌ oxyhaemoglobin

Haemoglobin + carbon monoxide → carboxyhaemoglobin

126
Q

what colour is (MnO4)-

A

purple

127
Q

colour change when fe3+ reacts with I-

A

orange brown Fe3+ reduced to pale green fe2+

pale green obscured by the oxidation of I- to I2 - brown colour

128
Q

conditions for oxidation of Fe2+

A

H+/MnO4-

129
Q

conditions for reduction of Fe3+

A

I–

130
Q

write out equation for oxidation of fe2+ AND colour changes

A
131
Q

write out the equation for the reduction of Fe3+ AND colour change

A
132
Q

what colour are dichromate ions

A

orange

133
Q

what colour are chromium (III) ions

A

green

134
Q

conditions for reduction of dichromate ions

A

Zn/H+,

135
Q

write out the equation for the reduction of dichromate ions AND colour change

A
136
Q

what happens if an excess if zinc is added to dichromate ions

A

chromium 3+ ions reduced further to chromium 2+

137
Q

what colour is chromium 2+

A

pale blue

138
Q

write out the equation for the reduction of chromium in excess zinc AND colour change

A
139
Q

conditions for oxidation of Cr3+

A

hot alkaline hydrogen peroxide

hydroxide ions

140
Q

write out the equation of the oxidation of Cr3+

A
141
Q

conditions for reduction of Cu2+

A

I- (excess)

142
Q

write out the equation for reduction of Cu2+ AND colour change

A
143
Q

what happens in aqueous conditions for copper

A

Cu+ readily disproportionates.

144
Q

compound where Cu has oxidation state 1

A

Cu2O - copper oxide

145
Q

example of disproportionation of Cu+ ions

A

Copper oxide reacts with hot dilute sulfuric acid

Chemistry - Module 5 (7 decks)

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