Principles of Transition Metal Chemistry (Edexcel A Level Chemistry): Exam Questions

This question is about catalytic converters.

Catalytic converters contain metals such as platinum.

Describe the bonding in platinum.

You may include a diagram in your answer.

A catalytic converter decreases the emissions of gases, such as carbon monoxide and nitrogen monoxide, from an internal combustion engine.

Describe the stages in a catalytic converter that result in this decrease.
No equations are required.

This question is about transition metals.

Which of these ions has the electronic configuration [Ar]3d⁵?

In which of these complex ions does the transition metal have the oxidation number +3?

Which type or types of bonding exist within the complex ion [Cr(H₂O)₆]³⁺?

Which best explains why [Cu(NH₃)₂]⁺ ions are colourless?

Glycinate ions are bidentate ligands and can be represented by the structure

Complete the diagram below to show the structure of the [Cu(NH₂CH₂COO)₂] complex, which is square planar.

Manganate(VII) ions, Mn, react with ethanedioate ions in acid solution.

2Mn + 5C₂+ 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O

The reaction starts slowly, the rate of reaction then increases, before it decreases again. Explain this sequence.

This is a question about catalysis.

The reaction between iodide ions and peroxodisulfate ions is catalysed by iron(II) ions.

2I^– + S₂O₈^2– I₂ + 2SO₄^2–

i) Give a reason why the reaction between iodide ions and peroxodisulfate ions has a high activation energy and is therefore very slow without a catalyst.

(1)

ii) Explain, with the aid of two equations, how the iron(II) ions catalyse this reaction. State symbols are not required.

(3)

The oxidation of sulfate(IV) ions to sulfate(VI) ions is catalysed by cobalt(II) ions in acidic solution. The role of cobalt(II) ions is similar to that of iron(II) ions in (a).

SO₃^2– + ½O₂ SO₄^2–

Deduce two ionic equations to show how cobalt(II) ions catalyse the reaction in acidic solution. State symbols are not required.

The rate of oxidation of ethanedioate ions by manganate(VII) ions starts slowly and then rapidly increases.

What is the catalyst in this reaction?

The trend in the strength of gaseous adsorption by three transition elements is

tungsten  >  platinum  >  silver

Silver is not suitable as a replacement for platinum in a catalytic converter because the adsorption of gases is too weak to allow significant chemical reaction.

Give a possible reason why tungsten would also not be a suitable replacement for platinum in a catalytic converter. Refer to the mechanism of heterogenous catalysis in your answer.

“Cobalt(II) ions combine with substances in solution to form complex ions with different coordination numbers.”

Discuss this statement by referring to two complex ions containing cobalt(II).

Include

• reference to any difference in colour

• a definition of any terms used

• an explanation of the different shapes

Colour is often used in chemistry to identify substances.

Compare and contrast the origin of the colour of a copper(II) complex with the origin of the colour of the copper(II) ion in a flame test.

You do not need to state any specific colours.

Transition metals form complex ions.

Complex ions have a central metal ion surrounded by ligands.

i) Give a reason why the ammonium ion cannot act as a ligand.

(1)

ii) Explain why the complex ions [Co(NH₃)₆]²⁺ and [Co(H₂O)₆]²⁺ are coloured and have different colours.

(4)

Which of these complexes is used in the treatment of cancer?

Compare and contrast the complex ions formed by cobalt(III) ions with the ligand ethane-1,2-diamine and with the ligand EDTA^4–.

Ignore any difference in colour.

Hydrated chromium(III) chloride, CrCl₃.6H₂O, dissolves in water to form a number of different complex ions containing both chloride and water ligands.

The general formula of these complex ions is [Cr(H₂O)_x(Cl)_y]^(3–y)+

In an experiment, 0.10 mol of a complex reacted with excess silver nitrate solution to produce 0.20 mol of silver chloride.

Chloride ions which are ligands within the complex do not react with silver nitrate.

Deduce the formula of this chromium(III) complex ion. Justify your answer.