Syllabus Edition

First teaching 2020

Last exams 2024

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Properties of Transition Elements (A Level Only) (CIE A Level Chemistry)

Exam Questions

2 hours9 questions
1a1 mark

This question is about transition metals. 

Explain what is meant by a transition metal. 

1b2 marks
i)
State the electronic configuration of Ti2+.
 
[1]
 
ii)
Explain, using the electronic configuration, why zinc is found in the d-block of the periodic table but not classed as a transition metal.
 
[1]
1c3 marks

Table 1.1 shows sketches of the shapes of some atomic orbitals.

 
Table 1.1 
 
Shape of orbital dxy-orbital s-orbital pz-orbital
Type of orbital    

 
 

Identify the type of orbital, s, p, or d.

1d2 marks

Transition metals have characteristic properties. One of these properties is that they form coloured ions.

State two other properties that transition metals or their ions exhibit.

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2a2 marks

This question is about transition metal complexes. 

Define the terms ligand and complex.

 

Ligand = ............................................................ 

Complex = ..........................................................

2b1 mark

Transition metals can form complexes with different ligands.

 

Identify one species from the following list that does not act as a ligand. Explain your answer.

 
CO         H2O         SCN-          H2 
2c2 marks

A complex contains one Co2+ ion, four ammonia molecules and two chloride ions.

 
i)
State the formula of this complex.
 
[1]
 
ii)
Name the shape of this complex. 
 
[1]
2d2 marks

The H2O ligands in [Fe(H2O)6]3+ can be exchanged for other ligands. 

 

Predict the shape of the complex ions formed after the following substitutions.

 

i)
All the H2O ligands are exchanged for OH ligands.
 
[1]
 
ii)
The six H2O ligands are exchanged for four Cl ligands.
 
[1]
2e2 marks

Cisplatin can be used to treat some types of cancer.

 

It is a square planar transition metal complex with a central platinum(II) ion, two chloride ligands and two ammonia ligands.

 

Complete the three-dimensional diagram in Fig. 2.1 to show the shape of cisplatin. Label and state the value of one bond angle.

 
 
 
 
Pt
 
 

 
Fig. 2.1 

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3a1 mark

The d-orbitals of a transition metal are involved in the formation of complexes.

In terms of energy, explain what is meant by degenerate orbitals. 

3b3 marks

Fig. 3.1 shows the shape of the dxy orbital. 

 
dxy-orbital
 
Fig. 3.1
 

The dxz orbital has a similar shape but the lobes are between the x-axis and z-axis and the dyz orbital has a similar shape but the lobes are between the y-axis and z-axis.

 
i)
State the difference between the shape of a dxy orbital and the shape of a dx2–y2 orbital.
 
[1]
 
ii)
Complete the three-dimensional diagram in Fig. 3.2 to show the shape of a dz2 orbital. 
 
xyz-orbital-axes
 
Fig. 3.2 
 
[2] 
3c1 mark

Suggest what causes d-orbitals in a transition metal ion to change from degenerate to non-degenerate.

3d2 marks

The splitting of degenerate d-orbitals gives two sets of non-degenerate d-orbitals at different energy levels.

 

Complete Table 3.1 to show the different energy levels of the non-degenerate d-orbitals in octahedral and tetrahedral complexes.

 
Table 3.1 
 
  Higher energy Lower energy
Octahedral    
Tetrahedral    

 

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1a1 mark

Define a transition element.

1b3 marks
i)
NH3 acts as a monodentate ligand. State what is meant by monodentate ligand.

[2]

ii)
Aqueous silver ions, Ag+ (aq), react with aqueous ammonia, NH3 (aq), to form a linear complex.

Suggest the formula of this complex, including its charge.

[1]

1c5 marks

There are two isomeric complex ions with the formula [Cr(NH3)4Cl2]+. One is green and the other is violet.

i)
Suggest the type of isomerism shown by these two complex ions.

 [1]

ii)

Explain why these two complex ions are coloured and why they have different colours.

[4]

1d2 marks

The ligand ethane-1,2-diamine, H2NCH2CH2NH2, is represented by en.
Nickel forms the complex ion [Ni(en)3]2+ in which it is surrounded octahedrally by six nitrogen atoms.

Draw three-dimensional diagrams to show the stereoisomers of [Ni(en)3]2+.

q-6d-9701-y22-sp-4-cie-ial-chem
1e3 marks

Ethane-1,2-diamine is a useful reagent in organic chemistry.

i)
Explain how the amino groups in ethane-1,2-diamine allow the molecule to act as a Brønsted-Lowry base.

[2]

ii)
Write an equation for the reaction of ethane-1,2-diamine with an excess of hydrochloric acid.

[1]

1f3 marks
i)
Under certain conditions ethane-1,2-diamine reacts with ethanedioic acid, HOOCCOOH, to form the polymer Z.
Draw the structure of polymer Z, showing two repeat units.

[2]

ii)
Name the type of reaction occurring during this polymerisation.
[1]

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2a6 marks

Copper, vanadium and iron are all transition elements.

i)
Give the full electronic configuration of a Cu atom and a Cu2+ ion.
 
[2]
 
ii)
State four characteristic features of the chemistry of copper and its compounds.
 
[4]
2b5 marks

The chloride ion is a monodentate ligand. When concentrated hydrochloric acid is added to [Cu(H2O)6]2+ (aq) ions the water ligands are replaced.
 

i)
Define the term monodentate ligand.
 
[1]
 
ii)
Write an equation for the reaction that occurs when concentrated hydrochloric acid is added to [Cu(H2O)6]2+ (aq).
 
[1]
 
iii)
Draw the structure of the complex ion formed and name the shape it takes.
 
[2]
 
iv)
State the change in coordination number. 
 
[1]
2c3 marks

Vanadium (V) oxide is the catalyst used in the contact process as shown by the reactions:

SO2 + V2O5 → SO3 + V2O4

V2O4 + ½O2 → V2O5

i)
Using the equations, write an overall equation for the reaction.
 
[1]
 
ii)
Using the equations, explain why V2O5 is a catalyst.
 
[1]
 
iii)
Explain why V2O5 is able to act as a catalyst in this reaction.
 
[1]
2d3 marks

When iron(II) compounds dissolve in water they form [Fe(H2O)6]2+, the hexaaquairon(II) complex.

i)
State the full electronic configuration of an iron(II) ion.
 
[1]
 
ii)
Predict the shape and bond angle of the hexaaquairon(II) complex.
 
[2]

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3a2 marks

A solution is made by dissolving CuSO4•5H2O in an excess of aqueous ammonia. This solution contains the copper complex [Cu(NH3)4]2+.

i)
Write an expression for the Kstab of [Cu(NH3)4]2+.
 
Kstab =
 
[1]
 
ii)
State the colour of the solution of [Cu(NH3)4]2+.
 
[1]
3b1 mark

The solution of [Cu(NH3)4]2+ is heated gently in a fume cupboard so that NH3 is released. Some NH3 remains in solution and some forms NH3 gas. The colour of the solution changes; a precipitate of Cu(OH)2 forms and is collected.

A sample of Cu(OH)2 is added to concentrated hydrochloric acid. A reaction takes place forming a coloured copper complex, Y.

A sample of Cu(OH)2 is added to dilute sulfuric acid. A reaction takes place forming a coloured copper complex, Z.

[Cu(NH3)4]2+, Y and Z are different colours.

Suggest an equation for the reaction of [Cu(NH3)4]2+ to form Cu(OH)2 as the aqueous solution of [Cu(NH3)4]2+ is heated.

3c2 marks

Suggest an equation for the reaction of Cu(OH)2 with concentrated hydrochloric acid, forming Y.

3d2 marks

Complete Table 3.1 with the colour and geometry of complex Y and the colour, geometry and formula of complex Z.

Table 3.1

  Y Z
colour of complex    
geometry of complex    
formula of complex    
 
3e5 marks

Explain why complexes Y and Z are coloured and why their colours are different.

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4a2 marks

This question is about the geometry and colours of transition metal complexes. 

Explain why transition metals exhibit variable oxidation states compared to the elements in group 1.

4b3 marks

Transition metal compounds and ions are often coloured. For example, [Cr(H2O)6]3+ is green. 

Explain why [Cr(H2O)6]3+ and other complex ions are coloured.

4c3 marks

Zinc and cobalt ions react with water to form the complexes [Zn(H2O)4]2+ and [Co(H2O)6]2+.

i)
Explain how water acts as a ligand in forming these complexes.
 
[2]
 
ii)
Predict the shape of [Co(H2O)6]2+.
 
[1]
4d4 marks

Explain why solutions containing [Co(H2O)6]2+ are coloured but solutions containing [Zn(H2O)4]2+ are not.

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