Brainscape's Knowledge GenomeTM

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


See full index

CHEMISTRY OCR A > 5.7 TRANSITION ELEMENTS > Flashcards

5.7 TRANSITION ELEMENTS Flashcards

1
Q

What are D-block elements?

A

D-block elements:
- located between group 2 and group 13
- 3rd subshell has the highest energy
- electrons added to 3d orbitals
- all metallic (high mp and bp, shiny, conduct electricity and heat)
- used in coinage, construction, production of tools, electrical cables, water pipes, aerospace industry, medical applications (joint replacement and cosmetic dentistry)

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

What are the anomalies for electron configuration of d-block elements?

A

Chromium and copper do not follow the expected principle for electron configuration. This is due to stability, a half filled d5 subshell and a fully filled d10 subshell give additional stability to atoms of Cr and Cu

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

What is the configuration of ions for d block elements?

A

Configuration of ions:
- lose 4s electrons before any others
- this means that when forming an atom, the 4s orbital fills before the 3d orbitals but when forming an ion the 4s empties before the 3d

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

What are transition elements?

A

Transition elements are d block elements that form at least one ion with a partially filled d orbital
- although scandium and zinc are d block elements they do not match the definition and are not transition elements
- scandium only forms Sc3+ by losing two 4s electrons and one 3d electron (removing the 3d orbital)
- zinc only forms Zn2+ by the loss of two 4s electrons (leaving a full 3d orbital)

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

What are the properties of transition metals and compounds?

A

Properties:
- form compounds in which the transition element has different oxidation states
- they form coloured compounds
- the elements and their compounds can act as catalysts

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

Variable oxidation states.

A

Variable oxidation states:
- transition elements form compounds with more than one oxidation state
- e.g iron forms two chlorides FeCl2 and FeCl3
- the number of oxidation states increase across the transition elements to manganese, then decreases
- all transition elements form compounds with an oxidation number of +2, resulting from the loss of two electrons
- each oxidation state often has a characteristic colour
- a species containing a transition element in its highest oxidation state is often a strong oxidising agent

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

Formation of coloured compounds.

A

Formation of coloured compounds:
- compounds and ions of transition elements are frequently coloured
- potassium dichromate (VI) is bright orange, cobalt (II) chloride is pink-purple, nickel (II) sulfate is green, whilst hydrated copper (II) sulfate is blue
- the solid compounds can be dissolved in water to produced coloured solutions
- the colour of a solution is linked to the partially filled d-orbitals of the transition metal ion
- the colour of a solution can vary with different oxidation states
= e.g iron (II) is pale green, iron (III) is yellow
= e.g chromium (III) is green and chromium (VI) is yellow or orange

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

Transition metals as catalysts.

A

Transition metals as catalysts:
- important catalysts used in a variety of industrial processes and in the lab
= the haber process is catalysed by a finely divided iron catalyst
= contact process is catalysed by vanadium (V) oxide V2O5
= hydrogenation of vegetable fats in the manufacture of margarine uses a nickel catalyst
= catalytic decomposition of hydrogen peroxide forming oxygen uses manganese (IV) oxide MnO2
- heterogenous catalysts ^
- homogenous catalysts
= reaction between iodide ions and peroxodisulfate ions S2O8-
= the reaction of zinc with acids is catalysed by the presence of Cu2+

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

What are complex ions?

A

Complex ions:
- metal ions form complex ions by accepting electron pairs from other ions or molecules
- the bonds formed are dative covalent bonds (coordinate bonds)
- an ion or molecule (with a lone pair of electrons) that can form such bonds with a transition metal are known as ligands
- all complex ions have a metal ion centre of ligands surrounding it (usually 4-6)
- the coordination number refers to the number of dative covalent bonds

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

What are monodentate ligands?

A

Monodentate ligands form one dative covalent bond with metal ion
Cl- OH - CN- NH3 H20

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

What are bidentate ligands?

A

Bidentate ligands form two dative covalent bonds with metal ion
H2NCH2CH2NH2 C2O4^2-

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

What is stereoisomerism (cis trans) in complex ions?

A

Stereoisomerism:
- square planar complexes or the form [MA2B2]^n exist in two forms
- at least one pair of identical ligands at 180 = trans
- at least one pair of identical ligands at 90 = cis

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

How is optical isomerism shown in complex ions?

A

Optical isomerism:
- octahedral complexes with bidentate ligands can exist as a pair of enatiomers (optical isomers)

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

What are the properties of ligands?

A

Properties of ligands:
- some ions/molecules like H2O do not make particularly good ligands and can be replaced by better ligands
- NH3 is a better ligand due to nitrogen being less electronegative than oxygen
- Cl- is a better ligand as it is negatively charged, making it electrostatically attracted to the positive transition metal ion

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

What is cis-platin?

A

Cis-platin:
- used in medicine as an anti-cancer drug
- works by forming a platinum complex inside of a cell which binds to DNA and prevents the DNA of the cell from replication (targets tumour cells)
- use can lead to kidney damage

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

What colour is Ti3+?

A

Ti3+ is purple/lilac.

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

What colour is V2+?

A

V2+ is purple/lilac.

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

What colour is V3+?

A

V3+ is green.

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

What colour is V4+?

A

V4+ is blue.

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

What colour is V5+?

A

V5+ is yellow.

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

What colour is Cr2+?

A

Cr2+ is blue.

22
Q

What colour is Cr3+?

A

Cr3+ is green.

23
Q

What colour is Cr6+?

A

Cr6+ is orange.

24
Q

What colour is Mn2+?

A

Mn2+ is pink.

25
Q

What colour is Mn4+?

A

Mn4+ is brick red.

26
Q

What colour is Mn6+?

A

Mn6+ is green.

27
Q

What colour is Mn7+?

A

Mn7+ is purple/lilac.

28
Q

What colour is Fe2+?

A

Fe2+ is pale green.

29
Q

What colour is Fe3+?

A

Fe3+ is pale yellow/brown.

30
Q

What colour is Co2+?

A

Co2+ is pink.

31
Q

What colour is Co3+?

A

Co3+ is green.

32
Q

What colour is Ni2+?

A

Ni2+ is green.

33
Q

What colour is Cu2+?

A

Cu2+ is blue.

34
Q

What is the equation and what is formed when Cu2+ ions are mixed with NaOH?

A

When Cu2+ mixed with NaOH:
Cu2+ + 2OH- = Cu(OH)2
- blue solution reacts to form a blue precipitate of copper II hydroxide
- the precipitate is insoluble in excess NaOH

35
Q

What is the equation and what is formed when Fe2+ ions are mixed with NaOH?

A

When Fe2+ mixed with NaOH:
Fe2+ + 2OH- = Fe(OH)2
- pale green solution reacts to form a green precipitate of iron II hydroxide
- the precipitate is insoluble in excess NaOH but turns brown at its surface on standing in air as iron II is oxidised to iron II
Fe(OH)2 = Fe(OH)3

36
Q

What is the equation and what is formed when Fe3+ ions are mixed with NaOH?

A

When Fe3+ mixed with NaOH:
Fe3+ + 3OH- = Fe(OH)3
- pale yellow solution reacts to form an orange brown precipitate of iron III hydroxide
- the precipitate is insoluble in excess NaOH

37
Q

What is the equation and what is formed when Mn2+ ions are mixed with NaOH?

A

When Mn2+ mixed with NaOH:
Mn2+ +2OH- = Mn(OH)2
- pale pink solution reacts to form a light brown precipitate of manganese II hydroxide which darkens on standing in air
- the precipitate is insoluble in excess NaOH

38
Q

What is the equation and what is formed when Cr3+ ions are mixed with NaOH?

A

When Cr3+ mixed with NaOH:
Cr3+ + 3OH- = Cr(OH)3
- violet solution reacts to form a grey green precipitate of chromium III hydroxide
- the precipitate is soluble in excess NaOH forming a dark green solution
Cr(OH)3 + 3OH- = [Cr(OH)6]3-

39
Q

What is the precipitation reaction when Cu(OH)2 is mixed with excess NH3?

A

When Cu(OH)2 mixed with NH3:
Cu(OH)2 + 4NH3 = [Cu(NH3)4(H2O)2]3+
- blue precipitate dissolves in excess NH3 to form a deep blue solution containing [Cu(NH3)4(H2O)2]3+

40
Q

What is the precipitation reaction when Cr(OH)3 is mixed with excess NH3?

A

When Cr(OH)3 mixed with NH3:
Cr(OH)3 + 3NH3 = [Cr(NH3)6]3+
- green precipitate dissolves in excess NH3 to form a purple solution containing [Cr(NH3)6]3+

41
Q

What occurs when Fe2+, Fe3+ and Mn2+ are mixed with excess NH3?

A

When Fe2+, Fe3+ and Mn2+ are mixed with excess NH3, the precipitates do not dissolve and form Fe(OH)2, Fe(OH)3 and Mn(OH)2.

42
Q

What happens when carbonate ions are mixed with dilute nitric acid?

A

When carbonate ions mixed with HNO3:
CO3^2- + 2H+ = CO2 + H2O
- effervescence as carbon dioxide is evolved.

43
Q

What happens when sulfate ions are mixed with Barium ions?

A

When sulfate ions mixed with Ba2+
Ba2+ + SO4^2- = BaSO4
- white precipitate of BaSO4 formed.

44
Q

What happens when halide ions are mixed with silver ions?

A

When halides mixed with Ag+:
Cl- + Ag+ = AgCl
- white precipitate of AgCl formed
- precipitate soluble in dilute NH3
Br- + Ag+ = AgBr
- cream precipitate of AgBr formed
- precipitate soluble in concentrated NH3
I- + Ag+ = AgI
- yellow precipitate of AgI formed
- precipitate insoluble in NH3

45
Q

What is the equation and what is formed in the redox reactions involving Fe2+ and Fe3+?

A

Oxidation of Fe2+ to Fe3+:
MnO4^- + 8H+ + 5Fe2+ = Mn2+ + 5Fe3+ + 4H2O
- acidic conditions, used as a basis for a redox titration
- Fe2+ oxidised to Fe3+
- MnO4^- reduced to Mn2+
- purple solution decolourised by Fe2+ ions to form a colourless solution (purple to colourless)

Reduction of Fe3+ to Fe2+:
2Fe3+ + 2I- = 2Fe2+ + I2
- Fe3+ reduced to Fe2+
- I- oxidised to I2
- orange-brown solution reduced to pale green, however colour change is obscured by the oxidation of I- (no colour change)

46
Q

What is the equation and what is formed in the redox reaction involving Cr2O7^2- and Cr3+?

A

Reduction of Cr2O7^2- to Cr3+:
Cr2O7^2- + 14H+ + 3Zn = 2Cr3+ + 7H2O + 3Zn2+
- acidified Cr2O7^2- and addition of Zn as zinc is most powerful oxidising agent
- orange solution to green
- with an excess of zinc, chromium III ions are reduced further to chromium II ions
Zn + Cr3+ = Zn2+ + Cr2+
- green solution to pale blue

47
Q

What is the equation and what is formed in the redox reaction involving Cr3+ and CrO4^2-?

A

Oxidation of Cr3+ to CrO4^2-:
3H2O2 + 2Cr3+ + 10OH- = 2CrO4^2- + 8H2O
- chromium is oxidised from +3 in Cr3+ to +6 in CrO4^2-
- oxygen is reduced from -1 in H2O2 to -2 in CrO4^2-
- hot alkaline H2O2 used (powerful oxidising agent) used to oxidise chromium III to chromium IV

48
Q

What is the equation and what is formed in the redox reaction involving Cu2+ and Cu+?

A

Reduction of Cu2+ to Cu+:
2Cu2+ + 4I- = 2CuI + I2
- I- oxidised to I2
- Cu2+ reduced to Cu+
- pale solution forms white precipitate of CuI

49
Q

What is the disproportionation reaction involving Cu+ ions?

A

Disproportionation of Cu2+:
Cu2O + H2SO4 = Cu + CuSO4 + H2O
- Cu2O mixed with hot dilute H2SO4
- forms brown solid of Cu and a blue solution of CuSO4
- Cu+ ions simultaneously oxidised and reduced
- oxidised from +1 in Cu2O to 0 in Cu
- reduced from +1 in Cu2O to +2 in CuSO4

50
Q

What is the reaction of ammonium ions to form ammonia?

A

Ammonium to form ammonia:
NH4^+ + OH- = NH3 + H2O
- heated
- to test for ammonium ion, NaOH is heated gently with solution analysed
- if ammonia is evolved damp red pH indicator paper will turn blue, indicating presence of ammonium ions.

CHEMISTRY OCR A (28 decks)

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