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Edexcel A-Level Chemistry A2 17 Transition Metals and Their Chemistry Questions

Topic 17 questions move from definitions and electron configurations into ligands, complex ions, colour changes, catalysis and transition-metal redox chemistry.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Classify transition metals by stable ions with incompletely filled d orbitals.
  • Deduce Period 4 d-block atom and ion configurations, including Cr and Cu exceptions.
  • Use ligand, complex-ion and colour evidence to interpret transition-metal reactions.

Covered syllabus points

17.1—Transition metals are d-block elements that form one or more stable ions with incompletely-filled d-orbitals17.2—Deduce the electronic configurations of atoms and ions of the d-block elements of Period 4 (Sc-Zn) given their atomic number17.3—Why transition metals show variable oxidation number17.4—What is meant by the term ‘ligand’17.5—Dative (coordinate) covalent bonding is involved in the formation of complex ions17.6—A complex ion is a central metal ion surrounded by ligands17.7—Aqueous solutions of transition metal ions are usually coloured17.8—The colour of aqueous ions, and other complex ions, is a consequence of the splitting of the energy levels of the d-orbitals17.9—Why there is a lack of colour in some aqueous ions and other complex ions17.10—The meaning of the term ‘coordination number’17.11—Colour changes in transition metal ions may arise as a result of changes in: i oxidation number of the ion ii ligand iii17.12—H2O, OH- and NH3 act as monodentate ligands17.13—Why complexes with six-fold coordination have an octahedral shape, such as those formed by metal ions with H2O, OH- and NH317.14—Transition metal ions may form tetrahedral complexes with relatively large ions such as Cl-17.15—Square planar complexes are also formed by transition metal ions and that cis-platin is an example of such a complex which17.16—The terms ‘bidentate’ and ‘hexadentate’ in relation to ligands17.17—Haemoglobin is an iron(II) complex containing a polydentate ligand and that ligand exchange occurs when an oxygen molecule17.18—The colours of the oxidation states of vanadium (+5, +4, +3 and +2) in its compounds17.19—Redox reactions for the interconversion of the oxidation states of vanadium (+5, +4, +3 and +2), in terms of the relevant Eo17.20—Understand, in terms of the relevant E values, that the dichromate(VI) ion, Cr2O2- i can be reduced to Cr3+ and Cr2+ ions17.21—Dichromate(VI) ions can be converted into chromate(VI) ions through the equilibrium Cr2O7^2− + H2O ⇌ 2CrO4^2− + 2H+17.22—Record observations and write suitable equations for the reactions of Cr3+(aq), Mn2+(aq), Fe2+(aq), Fe3+(aq), Co2+(aq)17.23—Write ionic equations to show the meaning of amphoteric behaviour, deprotonation and ligand exchange in the reactions17.24—Ligand exchange, and an accompanying colour change, occurs in the formation of: i [Cu(NH3)4(H2O)2]2+ from [Cu(H2O)6]2+ via17.25—Understand, in terms of the positive increase in ∆Ssystem, that the substitution of a monodentate ligand by a bidentate or17.26—Transition metals and their compounds can act as heterogeneous and homogeneous catalysts17.27—A heterogeneous catalyst is in a different phase from the reactants and that the reaction occurs at the surface of17.28—Understand, in terms of oxidation number, how V2O5 acts as a catalyst in the contact process17.29—How a catalytic converter decreases carbon monoxide and nitrogen monoxide emissions from internal combustion engines by: i17.30—A homogeneous catalyst is in the same phase as the reactants and appreciate that the catalysed reaction will proceed via17.31—The role of Fe2+ ions in catalysing the reaction between I− and S2O8^2− ions17.32—The role of Mn2+ ions in autocatalysing the reaction between MnO4− and C2O4^2− ions17.33—CORE PRACTICAL 14 The preparation of a transition metal complex

Question 1

[Maximum number: 3]

This question is about mercury, Hg, and its compounds.
Mercury is a liquid element in the same group of the Periodic Table as zinc.
The electronic configuration of mercury is [Xe]4f145 d106 s2[\mathrm{Xe}] 4 \mathrm{f}^{14} 5 \mathrm{~d}^{10} 6 \mathrm{~s}^{2}.

Mercury forms compounds in either the +1 or +2 oxidation states.

Explain why mercury is classified as a d-block element but is not a transition element.
(3)

Question 2

[Maximum number: 1]

Which d-block elements of Period 3 do not follow the periodic pattern in the electronic configuration of their atoms?

A

chromium and copper

B

chromium and manganese

C

scandium and copper

D

scandium and zinc

Question 3

[Maximum number: 5]

This question is about the chemistry of vanadium.
The standard electrode potentials of some vanadium species are shown.

Table for Question 3 — Edexcel A-Level Chemistry A2

Question (a)

(a)

Explain the highest stable oxidation state formed by vanadium, by referring to its electronic configuration.

[ 3 ]

Question (b)

(b)

In the manufacture of sulfuric acid, vanadium(V) oxide, V_2 O_5, is the catalyst used in the conversion of sulfur dioxide to sulfur trioxide:

2SO2+O2⇌2SO32 \mathrm{SO}_{2}+\mathrm{O}_{2} \rightleftharpoons 2 \mathrm{SO}_{3}

Write two equations to show a possible mechanism for this reaction.
State symbols are not required.

[ 2 ]
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