Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry Year 2 > Transition Metals > Flashcards

Transition Metals Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

Transition metal

A

Any of the set of metallic elements occupying the central d block of the periodic table

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a transition metal defined as?

A

An element that has an incomplete d subshell either in the element or in one of its ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the common properties of the transition metals (period 4)?

A
  • they form complex ions
  • their ions are coloured
  • they show catalytic activity
  • their oxidation states are variable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why is scandium not considered a transition metal?

A

The normal scandium ion formed has no electrons in the d orbital

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is zinc not considered a transition metal?

A

Normal zinc ions have a complete d subshell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Complex ions with water ligands are called

A

Metal-aqua ions. They may be represented as Cu^2+ (aq) for example

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

From Mn^2+ to Cu^2+ the reactivity of divalent (2+) metal-aqua ions

A

Increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Complete ligand substitution

A

All ligands are replaced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Incomplete ligand substitution

A

Only some ligands are replaced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Is the substitution of a Cu^2+ aqua complex with ammonia complete or incomplete?

A

Incomplete because the complex ion with four ammonia and two water molecules is energetically more stable than the complexes with six water or six ammonia molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Is the reaction of ligand substitution reversible or irreversible?

A

Reversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is there a change in coordination number when halide ions undergo ligand substitution with complexes containing water and/or ammonia ligands only?

A

Halide ions are larger than water and ammonia ligands, therefore the metal ions can only coordinate 4 halide ions. Coordination number changes from 6 to 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give two examples of bidentate ligands

A

Ethylenediamine (H2NCH2CH2NH2) and ethanedioate (oxalate) (C2O4)^-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Give two examples of multidentate ligands

A

Ethylenediaminetetraacetate (EDTA^4-) and sarcophagine (SAR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are multidentate ligands also known as? Why?

A

Chelating agents as they form very stable complexes with transition metal ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a ligand?

A

A molecule or ion that can form a coordinate bond to a metal by donating a pair of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

A complex ion is

A

A metal ion surround by ligands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Give an example of a linear complex

A

[Ag(NH3)2]^+, complex formed in Tollen’s reagent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why are certain colours produced in transition metal compounds?

A

Some wavelengths of light are absorbed and others are reflected or transmitted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Quanta

A

Single packets of energy in light photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Frequency

A

The number of wavelengths of light passing a particular point in one second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When light is absorbed, electrons in the d orbital…

A

… move from the ground state to an excited state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

When light is absorbed, what factors affect the value of ΔE?

A
  • the ligand size
  • the strength of the ligand-metal bond in the complex
  • the shape of the complex
  • the coordination number
  • the oxidation state of the metal in the central ion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

The colour of a transition metal complex ion is due to

A

the absorption of light with energy that can excite an electron from a 3d orbital of lower energy to one of higher energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

When transition metal atoms form complex ions, what happens to the d orbital?

A

It is ‘split’ into two levels, one of higher energy and one of lower energy. This is because the electrons in the ligand repel the electrons in the 3d orbitals which are in close proximity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are strong-field ligands?

A

Ones that induce a large ΔE, e.g. CN^-, CO and P(C6H5)3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are weak-field ligands?

A

Those that induce a small ΔΕ, e.g. NH3, H2O and Cl^-

28
Q

What does the amount of light absorbed by a coloured solution depend on?

A
  • the nature of the ion (relates to ΔE)
  • the concentration of the solution
  • the distance the light has to travel through the solution (path length)
29
Q

What effect does a greater concentration have on the intensity of colour in a solution?

A

The colour will be more intense as there are more ions present in a given volume, meaning more will interact with the light

30
Q

What effect does a longer path length have on the intensity of colour in a solution?

A

Colour will be more intense as the light has to travel a greater distance, meaning more ions will interact with the light

31
Q

Spectrophotometer

A

An instrument used to carry out spectroscopy - the analysis of a compound by detecting its response to electromagnetic radiation

32
Q

Colorimeter

A

An instrument that measures the absorption of a range of radiation

33
Q

Complementary colour

A

A colour that a sample will absorb most

34
Q

Th concentration of coloured ions in solution can be determined by

A

using a colorimeter or spectrophotometer. The path length and nature of the coloured ion must be kept constant, the concentration can be determined by comparing to standard solutions

35
Q

Oxidation state

A

The charge that an element would have if it were totally ionically bonded. For an ion, it is the charge on the ion. In a covalent compound, it is the theoretical number assigned to each at atom in a molecule if it were an ionic compound.

36
Q

What does the ease of oxidation and redox potential for a transition metal depend on?

A

pH and nature of the ligand

37
Q

What species is reduced when distinguishing between aldehydes and ketones?

A

[Ag(NH3)2]^+ (Tollens’ reagent) is reduced to metallic silver

38
Q

In redox titrations with potassium manganate to estimate the number of iron(II) ions in solution, why is hydrochloric acid not used when acidifying the reaction mixture?

A

It can be oxidised to chlorine by manganate(VII) ions

39
Q

In redox titrations with potassium manganate to estimate the number of iron(II) ions in solution, why is nitric acid not used when acidifying the reaction mixture?

A

It is an oxidising agent and may oxidised the substance being analysed

40
Q

In redox titrations with potassium manganate to estimate the number of iron(II) ions in solution, why is conc. sulphuric acid not used when acidifying the reaction mixture?

A

It may oxidised the substance being analysed

41
Q

In redox titrations with potassium manganate to estimate the number of iron(II) ions in solution, why is ethanoic acid not used when acidifying the reaction mixture?

A

It is a weak acid, so the concentration of hydrogen ions will be insufficient

42
Q

What is the colour change at the end point of the titration between dichromate(VI) ions and iron(II) ions

A

From orange to blue/green

43
Q

What is the general sequence for redox titration calculations?

A

1 - write the half equations for oxidant and reductant
2- deduce the equation for the overall reaction
3 - calculate the number of moles of manganate or dichromate used
4 - calculate the ratio of moles of oxidant to moles of reductant from the redox equation
5 - calculate the number of moles in the sample solution of reductant
6 - calculate the number of moles in the original solution of reductant
7 - determine either the concentration of the original solution or the percentage of reductant in a known quantity of sample

44
Q

Adsorption

A

The process in which (usually) a gas bonds to the surface of a solid catalyst. The gas (or its products) is released after reaction occurs

45
Q

Desorption

A

The process in which a substance (usually a gas) is released from the surface of a solid catalyst following reaction

46
Q

Why can adsorption of a reactant onto a metal surface speed up a reaction?

A
  • It weakens the bonds within the reactant molecules, reducing the activation energy.
  • It can cause a reactant molecules to break up into more reactive fragments, again reducing the activation energy.
  • It can hold a reactant in a particular position, increasing the chance of a favourable collision. - It can give a higher concentration of one reactant on the catalyst surface, increasing the chance of a favourable collision with another reactant
47
Q

Why is tungsten rarely used as a catalyst in heterogeneous catalysis?

A

It forms a very strong bond with some molecules, meaning that the product molecule will not be released and the reaction will not proceed

48
Q

What are two ways to maximise the surface area of a catalyst in heterogeneous catalysis?

A
  • use a support medium, ADD TO
  • use a fluidised bed, gases are blown through a very fine powder, powder ‘floats’ separating catalyst particles, so all surface area is available for reactions
49
Q

In heterogeneous catalysis, what is catalyst poisoning?

A

When impurities are absorbed onto the surface, blocking active sites and reducing the effectiveness of the catalyst; this has a cost implication

50
Q

How is catalyst poisoning prevented in catalytic converters?

A

Aluminium oxide is mixed with the catalyst. The aluminium oxide ‘stores’ the sulphur oxides under oxidising (running) conditions, and converts them to hydrogen sulphide under reducing accelerating conditions. This removes the sulphur periodically, so that it does not permanently poison the catalyst.

51
Q

What metals do catalytic converters contain?

A

A mixture of the metals palladium, platinum and rhodium, coated into a cerium oxide. These remove the unwanted products of combustion

52
Q

What are the conditions used in industry for the production of methanol?

A

A mixture of H and CO in a 2:1 ratio is passed over the catalyst chromium(III) oxide, Cr2O3, under high pressure at high temperature

53
Q

Why are catalysts used in industrial processes?

A

To increase the rate of reaction, allowing a much lower temperature to be used, yet maintaining sufficient output for the process to be cost-effective

54
Q

Haber process

A

Manufacturing process for the production of ammonia from nitrogen and hydrogen

55
Q

What is the catalyst used in the Haber process?

A

Iron is used as the heterogeneous catalyst. It is mixed with aluminium oxide and potassium oxide, which act as promoters. These are present in smaller amounts than the iron and improve the efficiency of the catalyst.

56
Q

The hydrogen used for the Haber process is obtained from methane, so trace amounts of steam and carbon monoxide are found as impurities in the hydrogen. How is the carbon monoxide removed?

A

By heating with an excess of steam in a two-stage process, first with an iron oxide catalyst and then with a zinc/copper catalyst. The products are carbon dioxide, which is easier to remove from the mixture, and hydrogen, which is used in the process.

57
Q

The contact process

A

The industrial process used to make sulphuric acid from sulphur, oxygen and water

58
Q

In the contact process, why is a vanadium(V) pentoxide catalyst, V2O5 used instead of platinum?

A

V2O5 is cheaper and less prone to poisoning by impurities

59
Q

Write out the two equations for the reactions that occur during the contact process

A

V2O5(s) + SO2(g) → 2VO2(s) + SO3(g)

4VO2(s) + O2(g) → 2V2O5(g)

60
Q

What is a heterogeneous catalyst?

A

A catalyst that is in a different phase to the reactants

61
Q

What is a homogenous catalyst?

A

A catalyst that is in the same phase as the reactants

62
Q

Autocatalysis

A

The ability of one of the products of a reaction to catalyse the reaction producing it. In autocatalysis the initial reaction rate increases, as more catalyst is produced

63
Q

What are the equations showing how Fe^2+ ions catalyse the reaction between I^- and S2O8^2-?

A

2Fe^2+ + S2O8^2- → 2Fe^3+ + 2SO4^-

2Fe^3+ + 2I^- → 2Fe^2+ + I2

64
Q

Why is the oxidation of iodide ions by peroxodisulphate ions slow, despite it being energetically favourable?

A

Both ions are negatively charged, so unlikely to make successful collisions with each other. This is why iron(II) ions are used as a catalyst

65
Q

Homogeneous catalysis proceeds via an

A

intermediate (or intermediates)

66
Q

Transition metal ions taking part in homogeneous catalysis usually go through a

A

temporary change in oxidation state

Chemistry Year 2 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions