Chemistry > Ch5.3 Transition elements > Flashcards

Ch5.3 Transition elements Flashcards

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1
Q

Which 2 elements are exceptions to the Aufbau principle?

A

chromium and copper

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2
Q

How is chromium an exception to the Aufbau principle?

A
  • 3d and 4s orbitals all contain 1 unpaired e-
  • 1s2 2s2 2p6 3s2 3p6 4s1 3d5
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3
Q

How is copper an exception to the Aufbau principle?

A
  • 3d orbital is filled completely leaving 4s half-filled
  • 1s2 2s2 2p6 3s2 3p6 4s1 3d10
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4
Q

Which electrons are lost first when ions are formed of the transition elements and why?

A
  • 4s electrons are lost before the 3d electrons unlike in all other elements
  • this is because, once filled, the 4s electrons have a slightly higher energy than the 3d electrons
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5
Q

Define transition metal

A

a d block element that has an incomplete d-subshell as a stable ion

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6
Q

What are the physical properties of transition metals?

A
  • high density
  • high melting and boiling points
  • shiny in appearance (lustrous)
  • conduct electricity
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7
Q

What are the chemical properties of transition metals?

A
  • have variable oxidation states
  • transition metal compounds form coloured solutions in water
  • catalysts
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8
Q

Can transition metals form ions with more than one stable oxidation state?

A

Yes
- all of the transition metals in period 4 do this (Ti to Cu)

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9
Q

Which compounds containing transition metals can act as strong oxidising agents?

A
  • compounds containing a transition metal in a high oxidation state
    eg. potassium manganate (VII) KMnO4
    eg. potassium dichromate (VI)
    K2Cr2O7
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10
Q

Explain what is meant by the statement: compounds of transition metals can undergo disproportionation

A
  • the transition metal species is both oxidised and reduced in the same reaction
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11
Q

Explain why transition metal compounds are often coloured

A
  • white light hits an object and part of the spectrum is absored by the object and the remaining is reflected which is the light we see
  • as light hits a transition metal ion, the electrons become excited (energised) and if there are some partially filled d sub-shells available, they can move up an energy level
  • as the electrons then drop back down, they release light energy which we see as colour

NOTE: a compound will only be coloured if the transition metal ion has partially filled d subshells

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12
Q

Define catalyst

A
  • a substance which speeds up a reaction by providing an alternative pathway with a lower activation energy and isn’t used up itself in the reaction
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13
Q

Why are transition metals good catalysts?

A
  • reactants are ADsorbed to the surface of a transition metal where it may gain or lose electrons and form an intermediate allowing a pathway with a lower activation energy
  • the transition metals can vary in oxidation states and once the reaction has occurred, the products are DEsorbed and the transition metal remains unchanged
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14
Q

What is the equation for hydrogen production?

A

Zn(s) + H2SO4(aq) –> ZnSO4(aq) + H2(g)

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15
Q

What is the catalyst for the reaction for hydrogen production?

A

CuSO4 or Cu2+ ion

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16
Q

What is the equation for the contact process?

A

2SO2 + O2 ⇌ 2SO3

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17
Q

What is the catalyst for the reaction of the contact process?

A

V2O5 or V5+ ion

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18
Q

What is the equation for oxygen production?

A

2H2O2 –> 2H20 + O2

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19
Q

What is the catalyst for the reaction for oxygen production?

A

MnO2 or Mn4+ ion

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20
Q

What is the equation for the Haber process?

A

N2 + 3H2 ⇌ 2NH3

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21
Q

What is the equation for the hydrogenation of ethene?

A

C2H4 + H2 –> C2H6

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22
Q

What is the catalyst for a catalytic converter?

A

Pt or Pd

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23
Q

What is the catalyst for vitamin B12?

A

Co

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24
Q

Define ligand

A

a molecule or ion that can donate a pair of electrons to the central transition metal ion to form a coordinate bond (dative covalent bond)

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25
Define coordinate bond
a bond in which one of the bonded atoms provides both electrons for the covalent bond
26
State some features of ligands
- all ligands have at least one lone pair of electrons - ligands can be neutral molecules or charged
27
What is a monodentate ligand?
- a ligand that donates just one pair of electrons to the central metal ion to form one coordinate bond - eg. Cl- , OH- , CN- , NH3 , OH2 , SCN- (thiocyanate)
28
What is a bidentate ligand?
- a ligand that contains 2 atoms which donate a pair of electrons each to the central metal ion - 2 coordinate bonds are formed per ligand
29
What is a multidentate ligand?
- a ligand that can form several coordinate bonds - eg. EDTA 4- (ethylenediaminetetraacetic acid)
30
Describe a linear complex ion giving its bond angles and occurrence
- 2 bonding regions in straight line - angle 180 degrees - occurs in Ag+ complexes
31
Describe a tetrahedral complex ion giving its bond angles and occurrence
- 4 bonding regions spread as far apart as possible - angle 109.5 degrees - occurs with large ligands eg. Cl-
32
Describe a square planar complex ion giving its bond angles and occurrence
- 4 bonding regions spread as far apart as possible in a planar restriction - angle 90 degrees - occurs in Pt 2+ complexes
33
Describe an octahedral complex ion giving its bond angles and occurrence
- 6 bonding regions spread as far as possible - angle 90 degrees - most common occurrence
34
What are the 2 types of stereoisomerism?
- cis-trans / E-Z - optical isomerism
35
What is stereoisomerism?
molecules or complexes with the same structural formula but with a different spatial arrangement of these atoms
36
What is cis-platin and how does it work?
- a very effective drug to fight cancer - it works by binding to DNA and stopping replication and cell division
37
What is optical isomerism?
- optical isomers are non-superimposable mirror images of each other
38
What do ligand substitution reactions involve?
- a ligand in a complex ion being removed and replaced by another ligand - common ligand substitution reactions involve the substitution of water molecules with another ligand
39
[Cu(H2O)6]2+ + NH3 (dropwise) equation, colours, type of reaction
[Cu(H2O)6]2+ + 2NH3 --> [Cu(H2O)4(OH)2] + 2NH4+ [Cu(H2O)6]2+ is pale blue solution [Cu(H2O)4(OH)2] is pale blue precipitate hydrolysis reaction ammonia acts as a base pulling a proton off two of the water ligands
40
[Cu(H2O)4(OH)2] + NH3 (excess after dropwise) equation, colours, type of reaction
[Cu(H2O)4(OH)2] + 4NH3 --> [Cu(H2O)2(NH3)4]2+ + 2H2O + 2OH- [Cu(H2O)4(OH)2] is a pale blue precipitate [Cu(H2O)2(NH3)4]2+ is a deep blue solution substitution reaction adding NH3 in excess causes ligand exchange to occur
41
[Cu(H2O)6]2+ + NH3 (excess straight away/overall reaction) equation, colours, type of reaction
[Cu(H2O)6]2+ + 4NH3 ⇌ [Cu(H2O)2(NH3)4]2+ + 4H2O [Cu(H2O)6]2+ is a pale blue solutiion [Cu(H2O)2(NH3)4]2+ is a deep blue solution substitution reaction
42
[Cr(H2O)6]3+ + NH3 (dropwise) equation, colours, type of reaction
[Cr(H2O)6]3+ + 3NH3 --> [Cr(H2O)3(OH)3] + 3NH4+ [Cr(H2O)6]3+ is a pale purple solution but can look green due to impurities [Cr(H2O)3(OH)3] is a dark green precipitate hydrolysis reaction ammonia is acting as a base when it pulls protons from 3 of the water ligands
43
[Cr(H2O)3(OH)3] + NH3 (excess after dropwise) equation, colours, type of reaction
[Cr(H2O)3(OH)3] + 6NH3 --> [Cr(NH3)6]3+ + 3H2O + 3OH- [Cr(H2O)3(OH)3] is a dark green precipitate [Cr(NH3)6]3+ is a purple solution substitution reaction (more likely to occur with conc NH3)
44
[Cr(H2O)6]3+ + 6NH3 (excess straight away/overall reaction) equation, colours, type of reaction
[Cr(H2O)6]3+ + 6NH3 ⇌ [Cr(NH3)6]3+ + 6H2O [Cr(H2O)6]3+ is a pale purple solution but can look green due to impurities [Cr(NH3)6]3+ is a purple solution substitution reaction
45
[Cu(H2O)6]2+ + conc HCl equation, colours, type of reaction
[Cu(H2O)6]2+ + 4Cl- ⇌ [CuCl4]2- + 6H2O OR [Cu(H2O)6]2+ + HCl ⇌ [CuCl4]2- + 6H2O + 4H+ [Cu(H2O)6]2+ is a pale blue solution [CuCl4]2- is a yellow solution (often looks green instead of yellow because there is a mix of the blue and yellow solutions present)
46
[Cu(H2O)6]2+ + NaOH (dropwise vs excess) equation, colours, type of reaction
dropwise full equation [Cu(H2O)6]2+ + 2OH- --> [Cu(H2O)4(OH)2] +2H2O dropwise simple equation Cu2+ + 2OH- --> Cu(OH)2 excess: no further reaction [Cu(H2O)6]2+ is a pale blue solution [Cu(H2O)4(OH)2] / Cu(OH)2 is a blue gelatinous precipitate hydrolysis reaction
47
[Fe(H2O)6]2+ + NaOH (dropwise vs excess) equation, colours, type of reaction
dropwise full equation [Fe(H2O)6]2+ + 2OH- --> [Fe(H2O)4(OH)2] + 2H2O dropwise simple equation Fe2+ + 2OH- --> Fe(OH)2 excess: no further reaction but precipitate darkens in time on the surface as it oxidises to [Fe(H2O)3(OH)3] (orange-brown precipitate) [Fe(H2O)6]2+ is a pale green solution [Fe(H2O)4(OH)2] / Fe(OH)2 is a dark green precipitate hydrolysis reaction
48
[Fe(H2O)6]2+ + NH3 (dropwise vs excess) equation, colours, type of reaction
dropwise [Fe(H2O)6]2+ + 2NH3 --> [Fe(H2O)4(OH)2] + 2NH4+ excess: no further reaction but the precipitate darkens with time on oxidation to [Fe(H2O)3(OH)3] [Fe(H2O)6]2+ is a pale green solution [Fe(H2O)4(OH)2] is a dark green precipitate hydrolysis reaction
49
[Fe(H2O)6]3+ + NaOH (dropwise vs excess) equation, colours, type of reaction
dropwise full equation [Fe(H2O)6]3+ + 3OH- --> [Fe(H2O)3(OH)3] + 3H2O dropwise simple equation Fe3+ + 3OH- --> Fe(OH)3 excess: no further reaction [Fe(H2O)6]3+ is a pale yellow solution [Fe(H2O)3(OH)3] is an orange-brown precipitate hydrolysis reaction
50
[Fe(H2O)6]3+ + NH3 (dropwise vs excess) equation, colours, type of reaction
dropwise [Fe(H2O)6]3+ + 3NH3 --> [Fe(H2O)3(OH)3] + 3NH4+ excess: no further reaction [Fe(H2O)6]3+ is a pale yellow solution [Fe(H2O)3(OH)3] is an orange-brown precipitate hydrolysis reaction
51
[Mn(H2O)6]2+ + NaOH (dropwise vs excess) equation, colours, type of reaction
dropwise full equation [Mn(H2O)6]2+ + 2OH- --> [Mn(H2O)4(OH)2] + 2H2O dropwise simple equation Mn2+ + 2OH- --> Mn(OH)2 excess: no further reaction but the precipitate darkens over time as it oxidises: 4Mn(OH)2 + O2 --> 2Mn2O3 + H2O [Mn(H2O)6]2+ is a very pale pink solution [Mn(H2O)4(OH)2] is a brown precipitate hydrolysis reaction
52
[Mn(H2O)6]2+ + NH3 (dropwise vs excess) equation, colours, type of reaction
dropwise [Mn(H2O)6]2+ + 2NH3 --> [Mn(OH)2(H2O)4] + 2NH4+ excess: no further reaction but the precipitate darkens over time as it oxidises: 4Mn(OH)2 + O2 --> 2Mn2O3 + H2O [Mn(H2O)6]2+ is a very pale pink solution [Mn(H2O)4(OH)2] is a brown precipitate hydrolysis reaction
53
[Cr(H2O)6]3+ + NaOH (dropwise) equation, colours, type of reaction
[Cr(H2O)6]3+ + 3OH- --> [Cr(H2O)3(OH)3] + 3H2O [Cr(H2O)6]3+ is a pale purple solution but can look green due to impurities [Cr(H2O)3(OH)3] is a dark green precipitate hydrolysis reaction
54
[Cr(H2O)3(OH)3] + NaOH (excess after dropwise) equation, colours, type of reaction
precipitate re-dissolves in excess hydroxide [Cr(H2O)3(OH)3] + 3OH- --> [Cr(OH)6]3- + 3H2O [Cr(H2O)3(OH)3] is a dark green precipitate [Cr(OH)6]3- is a dark green solution substitution reaction
55
What is the test for ammonium ions?
- add NaOH to NH4+ sample to make NH3 and H2O - NH3 will turn damp red litmus paper blue
56
What is the test for carbonate ions?
- add HCl to sample CO3 2- + 2H+ --> H2O + CO2 CO2 turns limewater cloudy when it's bubbled through
57
What is the test for sulphate ions?
- add HCl followed by BaCl2 Ba2+ + SO4 2- --> BaSO4 BaSO4 is a white precipitate
58
What is the test for halide ions?
- add nitric acid followed by silver nitrate AgCl, AgBr or AgI formed AgCl is white precipitate that dissolves in dilute or conc ammonia AgBr is a cream precipitate that dissolves in just conc ammonia AgI is a yellow precipitate that is insoluble in ammonia of any conc
59
How does haemoglobin relate to ligand substituution?
- haemoglobin is a complex protein of 4 polypeptide chains and each haemoglobin has 4 haem groups - each haem group has an Fe2+ ion at its centre, oxygen can reversibly bind to the Fe2+ ion which allows oxygen to be transported around the body
60
Describe the stucture of the Fe2+ complex ion in haemoglobin
- there are 4 coordinate bonds between the Fe2+ ion and the nitrogen atoms in the haem structure - a further coordinate bond is formed with globin protein - the final coordinate bond is formed with an O2 molecule which is then transported
61
Describe and explain how CO is related to haemoglobin and ligand substitution
- CO and O2 can both bind to haemoglobin at the same place - CO binds more strongly to the haemoglobin than O2 - if CO and O2 are both present in the lungs then CO will bind over O2 so there is less haemoglobin for O2 to bind to - CO molecules can replace O2 molecules and they are both ligands so this is ligand substitution - reaction of binding isn't reversible for CO
62
What happens to the body if CO and O2 are both present in the lungs at the same time?
- tissues are starved of O2 because it can't be transported
63
What symptoms can different concentrations of CO in the blood cause?
- low concs: headaches, nausea and potential suffocation - high concs: fatal
64
How is CO formed?
- during incomplete combustion of carbon-containing fuels - burning tobacco also releases CO which is why long-term smokers become short of breath
65
What are the physical properties of CO?
- colourless - odourless
66
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