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[OBSELETE] Edexcel - A Level Chem > Topic 15 > Flashcards

Topic 15 Flashcards

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1
Q

What are the basic properties of transition metals?

A
  • High density
  • Hard solids
  • Acts as a catalyst
  • All produce coloured compounds and coloured ions
  • High Melting and Boiling Points
  • Form Ions with different oxidation numbers
  • Form ions with incompletely-filled d-orbitals
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2
Q

What elements are in the d-block?

A

******Some are transition metals******

****Focus on the top row****

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3
Q

What is a transition element?

A

A transition element is a d-block element that can form at least one stable ion with a partially filled (incomplete) d-subshell

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4
Q

What d-block elements are not transition elements and why?

A
  • Since the d-subshell can only hold 10 electrons
  • Scandium and Zinc are not transition metals
  • They have completely filled d orbitals
  • They do not form a stable ion with a partially d-subshell
    • Scandium forms a 3+ ion
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5
Q

How do transition elements lose electrons?

A
  • Loose 4s electrons before 3d electrons
  • Making a stable ion
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6
Q

Why can transition metals have varying oxidation states?

A
  • The electron sits in the 4s and 3d energy levels which are very close
  • Electrons are gained and lost using a similar amount of energy
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7
Q

What is a complex ion

A

An ion in which a ******central metal atom (transition element)****** is surrounded by a group of ions or molecules (ligands)

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8
Q

How do you represent a complex ion showing the dative covalent bonds

A
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9
Q

What is a ligand?

A
  • Any tom, ion or molecule which can donate a pair of electrons to a metal ion (Lewis bases and nucleophiles)
  • Classified by the number of dative covalent or coordinate bonds that they can make
  • They form single coordinate bonds called unidentate or monodentate (only bonds to the metal once)
  • The lone pair of electrons will fill the d-orbital
  • Possible due to transition metal ions having a smaller ionic radius which gives rise to a stronger electrostatic field of attraction allowing for ligand formation
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10
Q

What are some examples of ligands

A

NH3, Cl-, OH-, H2O (All have lone pairs and can form a bond with a transition metal)

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11
Q

How do you name ligands?

A

Naming Ligands end in O

  • Chloro
  • Hydroxo
  • Aqua
  • Amine
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12
Q

What is a Lewis base

A

A base that donates a proton

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13
Q

Why is water a ligand

A
  • Each molecule makes a single bond with the metal ion
  • Where the oxygen which has lone pairs
  • Which is attracted to a positive charge
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14
Q

What is a bidentate ligand?

A
  • bidentate ligands contain two atoms that donate pair of electrons to form coordinate bonds
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15
Q

What is the structure of haemoglobin?

A
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16
Q

What happens when CO bonds to haemoglobin?

A
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17
Q

What are multidentate ligands?

A
  • Contain more than two atoms that donate pairs of electrons to form coordinate bonds
  • EDTA has 6 coordinate bonds
    • One EDTA ion per transition metal ion
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18
Q

What happens when the ligands bonds to the metal ion

A
  • The d-subshell is split into 2 when the ligands bond with the central metal ion
  • Orbitals gain energy and split into a 2,3 split
  • Energy Gap ∆E
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19
Q

What is the energy gap affected by?

A

The energy gap is affected by:

  • Central metal ion as well as the oxidation state
  • The type of ligand (monodentate, bidentate, multidentate)
  • Coordination number
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20
Q

What happens when light energy is absorbed by electrons in the ground state

A
  • Allows for electrons to absorb light energy from to ground state to an excited state
  • This requires the energy inputted to be equal to the energy gap
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21
Q

What happens to the frequency of the energy absorbed?

A
  • Some frequencies absorbed are of the visible light spectrum
  • Which is dependent on the frequencies absorbed by the size of the energy gap
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22
Q

In terms of the colour spectrum where does the energy gap frequency lie?

A
  • Red is the lowest frequency
  • The higher the energy gap the further along the spectrum the colour would be
  • Blue is the highest frequency
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23
Q

How is the colour shown in transition metals?

A
  • Frequencies that aren’t absorbed are reflected or transmitted
  • Meaning the rest of the unabsorbed colour forms a complementary colour
  • Example - Frequency for light blue is absorbed meaning the complementary colour red is produced
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24
Q

Why is a colour not shown in some d-block elements?

A

HOWEVER, complexes that have a full 3d or lack a 3d subs-shell with no electrons can migrate to a higher energy level meaning there is no colour produced

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25
Q

What is the coordinate number?

A

The number of different coordinate bonds to the metal ion

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26
Q

Why are H20, OH- and NH3 monodentate ligands?

A

They all have lone pairs which can form a dative covalent bond with a metal ion

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27
Q

What is the shape when and name when there is a complex with a coordinate number of 6?

A
  • Monodentate Ion
  • Octahedral Shape
28
Q

What is the name of a complex with different ligands attached to it?

A
29
Q

Why do complexes with Cl- form a different shape?

A
30
Q

What are the different shapes in comparison to the number of ligands and the bond angles for each?

A
31
Q

What is Cis-platin and its properties

A
32
Q

What are trans-platin and its properties?

A
33
Q

What shape do both trans and cis-platin have?

A
34
Q

Why is it important to filter which version of platin you get?

A
  • When you form platin a racemic mixture is formed
  • So there is an even amount of cis and trans
  • Meaning that its unknown whether the trans would be more toxic and outweigh the benefits of cis if you were to give to a patient and vice versa
  • That’s why you have to use plane polarised light to filter the trans from the cis
35
Q

What is the different ions of vanadium?

A
36
Q

What happens when you reduce vanadium from +5 to +2

A
  • Use ammonium vanadate(V)
    • In acidic solution the compound has VO2+
  • With zinc catalyst the ion reduces
  • Causing a change of yellow to blue to green

**VO2+ , VO 2+, V 3+**

37
Q

Why is a reduction of vanadium 5+ to 4+ feasible?

A
  • Electrode potential of the reduction reaction (first one) is more positive than the oxidation reaction is negative
    • E0cell=E0red−E0oxid
  • Zn is electron releasing with respect to VO2+
38
Q

Why is a reduction of vanadium +4 to +3 feasible

A
  • Electrode potential of the reduction reaction (first one) is more positive than the oxidation reaction is negative
    • E0cell=E0red−E0oxid
  • Zn is electron releasing with respect to VO +2
39
Q

Why is a reduction of vanadium 3+ to 2+ feasible?

A
  • Electrode potential of the reduction reaction (first one) is more positive than the oxidation reaction is negative
    • E0cell=E0red−E0oxid
  • Zn is electron releasing with respect to V 3+
40
Q

Why is the reduction of +2 to 0 not feasible

A
  • Electrode potential of the reduction reaction (first one) is less positive than the oxidation reaction is negative
    • E0cell=E0red−E0oxid
  • Zn is electron releasing with respect to V 2+vv
41
Q

What are the different variable oxidation states?

A
42
Q

How can Cr2O7 2- be reduced to 2Cr 3+?

A
  • Colour change from orange to green
  • Zinc is used as catalyst
  • Positive electrode potential because of voltage
43
Q

How can you reduce Cr3+ ions to Cr2+?

A
  • Zinc acts as a catalyst and increases in oxidation number because of an increase in oxidation number
  • Chromium is reduced with a decrease in oxidation number
  • Cr2+ I unstable and is readily oxidized back into Cr3+ from oxygen in air
  • Just feasible but not over +0.6V
  • Blue to green
44
Q

How are chromium ions oxidised?

A
  • Cr3+ ions oxsidised using hydrogen peroxide in alkaline slution
  • As pH can change the amount of CrO4 2-
  • Green to yellow
  • Chromate ions exist in equilibrium with dichromate
45
Q

How is pH related to dichromate and chromate resersable reaction

A
  • oxidation states don’t change → equilibrium
  • In acidic conditions you will have dichromate
  • In alkali conditions you will have chromate
46
Q

What is the general reaction of transition metals with sodium hydroxide or ammonia solution?

A
  • There would be proton transfer between the transition metal and ammonia solution/sodium hydroxide
  • Which then forms a precipitate which is coloured
47
Q

What happens when you add excess sodium hydroxide solution?

A
  • Proton Transfer between precipitate and sodium hydroxide
  • Precipitate dissolves
48
Q

What happens when excess ammonia is added?

A
  • Ligand exchange happens between ligands on complex and ammonia
  • Precipitate dissolves
49
Q

What is the reaction table for the transition metals?

A
50
Q

What are the reactions of chromium in aqueous sodium hydroxide and aqueous ammonia?

A
51
Q

What are the reactions of manganese in aqueous sodium hydroxide and aqueous ammonia?

A
52
Q

What are the reactions of iron(II) in aqueous sodium hydroxide and aqueous ammonia?

A
53
Q

What are the reactions of iron(III) in aqueous sodium hydroxide and aqueous ammonia?

A
54
Q

What are the reactions of Nickle in aqueous sodium hydroxide and aqueous ammonia?

A
55
Q

What are the reactions of Copper in aqueous sodium hydroxide and aqueous ammonia?

A
56
Q

What are heterogeneous catalysts?

A
  • One that is a different phase from the reactants

**Like breaking down hydrogen peroxide (liquid) with manganese oxide (solid)**

57
Q

Why are transition metals good heterogeneous catalysts?

A
  • Good solid catalyst
  • Change oxidation number by gaining or losing electrons in the d-orbital
    • Allowing for the transfer of electrons to speed up reactions
  • Reactions only happen on the surface
    • This is why we use powder rather than large lumps
    • Also why it’s used to coat an inert supporting material
58
Q

What is the step in the surface adsorption theory?

A
  1. Adsorption - 1+ reactants attach to the surface of the catalyst
  2. Reaction - Bonds are tweaked in the adsorbed reactants
  3. Desorption - Product becomes detached from the surface of the catalyst
59
Q

What are the steps in the contact process?

A
60
Q

Why are Carbon Monoxide and Nitrogen Monoxide bad?

A
  • Carbon monoxide interferes with oxygen transport around the body
  • Nitrogen monoxide is easily oxidised to nitrogen dioxide which forms acid rain
  • Both formed through the incomplete combustion of hydrocarbon file
61
Q

How does the catalytic converter convert these gases?

A
62
Q

What are homogenous catalysts?

A
  • A catalyst that is in the same phase as the reactants
  • All gases or all in an aqueous solution
  • Less common in industry
  • Forms an intermediate species for which a specific formular can be written
63
Q

What is the reaction with persulfate ion and what are the problems?

A
64
Q

What are the steps in the reaction with persulfate using Fe2+

A
65
Q

What is the steps in the reaction with persulfate using Fe3+?

A
66
Q

What is the steps in the reaction with persulfate using Fe3+?

A
67
Q

What elements beside transition elements can form metal ion complexes

A

Zinc and Aluminum

[OBSELETE] Edexcel - A Level Chem (27 decks)

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