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Chemistry Flashcards > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

What is a transition metal

A

Element in the ‘d block’ with a partially filled d-orbital

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2
Q

Special properties of transition metals

A

Form complexes
Form coloured ions
Variable oxidation states
Good catalysts

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3
Q

What is a complex

A

Central metal ipn surrounded by ligands

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4
Q

Common ligands are…

A

Cl-
H²O
NH³

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5
Q

What is a ligand

A

Molecules or ions with a lone pair of electrons that is able to form a co-ordinate bond with the central metal ion.

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6
Q

What is a co-ordination number

A

The number of co-ordinate bonds formed around the central metal ion.

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7
Q

Why do NH³ and H²O not change the co-ordination number when exchanged in ligand substitution reactions

A

Are both uncharged and similar in size

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8
Q

Colour of [Cu(H²O)²(NH³)⁴]²+ solution

A

Deep blue

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9
Q

Why does Cl- affect the co-ordination number

A

Cl- ligand is larger than NH³ and H²O

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10
Q

How many Cl- ligands can attach to a metal ion.

And shape of complex

A

4

Tetrahedral

Bond angle 109.5

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11
Q

What is a Bidentate Ligand

A

Ligands that form 2 co-ordinate bonds to the central ion and have 2 lone pairs of electrons

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12
Q

2 examples of Bidentate ligands

A

C²O⁴ (OOCCOO)
Lone pairs on single bond O’s

NH²CH²CH²NH²
Lone pairs on N’s

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13
Q

How many ligands does a Bidentate ligand replace
Does co-ordination number change

A

2
No change, still has 6 co-ordinate bonds

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14
Q

What is a Multidentate ligand

A

Ligand that can form up to 6 co-ordinate bonds to central metal ion.

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15
Q

Most common multidentste ligand

A

EDTA⁴-

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16
Q

What is the Chelate effect

A

Substituting unidentate ligands with bidentate or multidentare ligands to form more stable complexes.

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17
Q

What type of entropy is favourable in a ligand substitution reaction and why

A

Positive, more stable complex is being formed.
More favourable to have more moles on right than left

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18
Q

When will /\G be more favourable

A

The more negative /\G is the more favourable the reaction

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19
Q

What is the size of the enthalpy change (/\H) of ligand substitution reactions and why

A

/\H is very small
The bonds being formed are similar to the bonds broken
So overall enthalpy change is close to 0

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20
Q

What ligands commonly fork octahedral complexes

Bond angle of complex

A

NH³
H²O

90°

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21
Q

How is cis and trans isomers present in octahedral complexes

A

Cis - same unidentste ligands next to each other.
In planar positions

Trans - same unidentate ligands opposite each other.
E.g top and bottom

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22
Q

What complexes have optical isomerism

A

Octahedral complexes with bidentate ligands

Mirror images of each other

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23
Q

How is a tetrahedral complex formed

Bond angle

A

When complexes form with large ligands such as Cl-

Bond angle 109.5°

24
Q

Do tetrahedral complexes have optical isomerism

A

Yes

25
Q

What metals form square planar complexes

Bond angle

A

Platinum (Pt)
Nickel (Ni)

90°

26
Q

What metal(s) form linear complexes

Bond angle

A

Silver (Ag)

180°

27
Q

What is Cisplatin

A

Cis isomer of square planar complexes of Platinum (Pt)

28
Q

Common use of Cisplatin

A

Cancer therapy drug

29
Q

Why does only the cis isomer of the square planar platinum (Pt) work as a drug fir cancer therapy

A

Cells are chiral so only cis isomers are the correct orientation to ‘fit’ the cells.

30
Q

A Side effect of Cisplatin
And measure to reduce effect

A

Hair loss
Administered in small amounts to reduce effects

31
Q

What affects the colour of a transition metal ion
(3)

A

Co-ordination number
Type of ligands bonded to the ion
Oxidation state

32
Q

How is colour of the ions observed

A

White light shined on metal ion

Some wavelengths are absorbed

Remaining wavelengths are reflected back to the human eye

The reflected wavelengths forrespond to specific colours

33
Q

What happens to electrons in the d-orbital when they absorb energy from light

A

Move from ground state and are promoted to a higher state

34
Q

How to calculate /\E between two energy states of electrons

A

/\E
= (h x speed of light)/wavelength
= h x frequency
h=planks constant 6.63x10^-34

35
Q

What is colorimetry

A

Analytical technique that uses absorption of light to determine the concentration of coloured ions

36
Q

How is a calibration graph for colorimetry produced

A

Measuring solutions of known concentrations against absorbance

Relative abundance y axis
Concentration x axis

37
Q

How is a calibration graph for colorimetry used

A

To determine the concentration of an unknown substance

38
Q

Vanadium 4 possible colours with oxidation states and ions

A

5+ VO2+ yellow
4+ VO²+ blue
3+ V³+ green
2+ V²+ violet

You Better Get Vandadium

39
Q

What determines if a transition metal is reduced or oxidised

A

The pH of the reaction conditions

40
Q

What conditions are required to reduce a transition metal

A

Acidic conditions
H+ ions in excess

41
Q

What conditions are required to oxidise transition metals

A

Alkaline
OH- in excess

42
Q

3 reactions used in redox titrations

A

MnO4- + 8H+ + 5e- —> Mn²+ + 4H2O
Fe2+ —> fe³+ + e-
C2O4²- —> 2CO2 + 2e-

43
Q

In a redox titration what is the ratio between MnO4- ions to C2O4²- ions

A

2 : 5

44
Q

In a redox titration what is the ratio between Mno4- ions to Fe²+ ions

A

1 : 5

45
Q

In a redox titration what is the ratio between C2O4²- ions to Fe²+ ions

A

1 : 2

46
Q

What is catalyst

A

A substance that speeds up the rate of reaction without being used up

47
Q

Do catalysts affect equilibirum

A

No
But allow it to be reached faster

48
Q

2 types of catalysts

A

Homogenous
Heterogenous

49
Q

What is a heterogenous catalyst

A

A catalyst that is in phase or state to the species in the reaction

50
Q

Why are transition metals good catalysts

A

Variable oxidation states
Electrons are transfered to produce a reactive intermediate

51
Q

What transition metal is used in the haber process

A

Solid iron catalyst

52
Q

What transition metal is in the contact process

A

Vanadium oxide

53
Q

What is the contact process

A

Conversion of SO2 to SO3

54
Q

How does a catalyst work

A

Absorbs molecules onto active site

Active site increases proximity of molecules and weakens covalent bonds
Increases rate

Molecules are resorbed after they react

55
Q

How are catalysts poisoned

A

When impurities bpock active sites and prevent adsorption

56
Q

What is a homogenous catalyst

A

Catalysts that are in the same phase to the species of the reaction

57
Q

What is autocatalysis

A

Where a product in a reaction acts as a catalyst for the reaction

Chemistry Flashcards (4 decks)

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