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Wjec A Level Chemistry > 3.4 D-block > Flashcards

3.4 D-block Flashcards

1
Q

What is a transition metal?

A

Element that possesses a partially filled d sub-shell as an atom or in its stable ions

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2
Q

Can d-block transition metals attain various oxidation states in their compounds?

A

Yes

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3
Q

How can d-block transition metals attain various oxidation states in their compounds?

A

The energy levels of the 4s and 3d sub-levels are very close which means different numbers of electrons can be gained or lost using similar amounts of energy

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4
Q

Common oxidation states of chromium

A

+3
+6

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5
Q

Common oxidation states of manganese

A

+2
+4
+7

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6
Q

Common oxidation states of iron

A

+2
+3

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7
Q

Common oxidation states of cobalt

A

+2
+3

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8
Q

Common oxidation states of copper

A

+1
+2

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9
Q

Colour of aqueous solutions of compounds containing Cr3+

A

Green

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10
Q

Colour of aqueous solution of compounds containing CrO4^2-

A

Yellow

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11
Q

Colour of aqueous solution of compounds containing Cr2O7^2-

A

Orange

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12
Q

Colour of aqueous solution of compounds containing MnO4^-

A

Purple

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13
Q

Colour of aqueous solution of compounds containing Co^2+

A

Pink

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14
Q

Colour of aqueous solution of compounds containing Fe^2+

A

Pale green

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15
Q

Colour of aqueous solution of compounds containing Fe^3+

A

Red-brown

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16
Q

Colour of aqueous solution of compounds containing Cu^2+

A

Pale blue

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17
Q

What is a ligand?

A

Small molecule or ion with a lone pair of electrons which can bond to a transition metal ion

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18
Q

How many ligands does a tetrahedral transition metal complex have?
What angle are these to eachother?

A

4
109.5 degrees

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19
Q

How many ligands does a octahedral transition metal complex have?
What angle are these to eachother?

A

6
90 degrees

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20
Q

Is a tetrahedral or octahedral transition metal complex more common?

A

Octahedral

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21
Q

When is a transition metal ion coloured

A

In complexes

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22
Q

What energy do d-orbitals in a transition metal ion have when there is no ligand?

A

Degenerate
The same

23
Q

What happens to the energy levels of d-orbitals of transition metals when a ligand approaches?

A

Energy of 3 of the d-orbitals become different to the other 2
3 of lower energy
2 of higher energy

24
Q

How does an electron in one of the d-orbitals move between the sets of orbitals of different energies?

A

It needs to gain sufficient energy which is absorbed in the form of light

25
How many frequencies of light is absorbed as an electron gains energy in a d-orbital and why?
1 It corresponds to the energy gap between orbitals
26
Which colour is seen after light is absorbed by an electron from a d-orbital?
The complementary colour is reflected The colour seen is made up of the light frequencies that are NOT absorbed
27
Colour of compounds containing ((Cu(H2O)6))^2+ and which region of the spectrum is absorbed
Pale blue Light in red region is absorbed
28
Colour of complexes containing ((Fe(H2O)6))^3+ and which region of the spectrum is absorbed
Yellow Light in the purple region is absorbed
29
Are all transition metal complexes coloured and why?
No Electrons cannot move from lower to higher orbitals as they either have a full d sub-shell or an empty d-subshell
30
Examples of colourless transition metal complexes
Copper(I) - full d sub-shell Scandium(III) - empty d sub-shell
31
What is a ligand exchange reaction
Where a ligand in a complex ion is replaced by a different one
32
Why is concentrated hydrochloric acid used in ligand exchange reactions?
Provides a high concentration of chloride ions
33
Why can less chloride ions fit around a complex ion than other ligands eg water molecules
Chloride ions are bigger than water molecules so there isn't room to fit six around the central metal ion
34
What happens if conc HCl is added to a solution containing ((Cu(H2O)6))^2+
6 water molecules are replaced by 4 chloride ions
35
What happens if conc HCl is added to a solution containing ((Co(H2O)6))^2+
6 water molecules are replaced by 4 chloride ions
36
Colour of ((Cu(H2O)6))^2+
Blue
37
Colour of ((Cu(NH3)4(H2O)2))^2+
Royal blue
38
Colour of ((Co(H2O)6))^2+
Pink
39
Colour of ((CuCl4))^2-
Yellow-green
40
Colour of ((CoCl4))^2-
Blue
41
Homogenous transition metal catalysts
• same physical state as reactants • use variable oxidation states to oxidise/reduce a reactant • transition metal is returned to original oxidation state by a reaction with another molecule
42
Examples of homogeneous transition metal catalysts
• Manganese(IV) oxide in decomposition of hydrogen peroxide • Vanadium(V) oxide in the contact process, conversion of SO2 to SO3, vanadium(V) oxide is reduced from +5 to +4 and then reformed to original oxidation state
43
Heterogenous transition metal catalyst
• different physical state to the reactants • partially filled d-orbitals • provides a solid surface for reactants to be adsorbed and brought closer for more opportunity to react • molecules with lone pair of electrons can form coordinate bonds to the metal as there are available empty d-orbitals, this increases reactivity of species bonded to the metal
44
Examples of heterogenous transition metal catalysts
• iron - Haber process • nickel - hydrogenation of vegetable oil to form margarine
45
What happens when NaOH(aq) is added to most transition metal ions
A coloured precipitate forma
46
What does it mean if the precipitate of a transition metal ion dissolves on addition of excess NaOH(aq)
The transition metal is atmophoteric
47
Cr3+ Solution colour Observation after OH- is added Observation after excess OH- is added
Green Grey-green precipitate Precipitate dissolves giving a deep green solution
48
Fe2+ Solution colour Observation after OH- is added Observation after excess OH- is added
Pale green Dark green precipitate No change
49
Fe3+ Solution colour Observation after OH- is added Observation after excess OH- is added
Yellow Red-brown precipitate No change
50
Cu2+ Solution colour Observation after OH- is added Observation after excess OH- is added
Pale blue Pale blue precipitate No change
51
Ionic equation when NaOH(aq) is added to a solution containing Cr3+
Cr3+(aq) + 3OH-(aq) ---> Cr(OH)3(s) Cr(OH)3(s) + 3OH-(aq) ---> [Cr(OH)6]3-(aq)
52
Ionic equation when NaOH(aq) is added to a solution containing Fe2+
Fe2+(aq) + 2OH-(aq) ---> Fe(OH)2(s)
53
Ionic equation when NaOH(aq) is added to a solution containing Fe3+
Fe3+(aq) + 3OH-(aq) ---> Fe(OH)3(s)
54
Ionic equation when NaOH(aq) is added to a solution containing Cu2+
Cu2+(aq) + 2OH-(aq) ---> Cu(OH)2(s)

Wjec A Level Chemistry (19 decks)

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