A2 LEVEL CHEMISTRY

TRANSITION METALS 
PART I
ASSESSED HOMEWORK

Answer all questions
Max 114 marks

	
Name		…………………………………………………………..

Mark		……../114	……....%	Grade ………

1.	Mercury forms two ions, Hg22+ and Hg2+. The table shows the electronic configuration of mercury in these ions.
ion	electronic configuration	
Hg22+	[Xe]4f145d106s1	
Hg2+	[Xe]4f145d10	
	Use the electronic configurations to explain why mercury is not a transition element.
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[Total 1 mark]

2.	Iron forms several complex ions in which the oxidation state of iron is +3.
(i)	Complete the electronic configuration for an iron(Ill) ion, Fe3+.
1s22s22p6 .......................................................................................................
[1]
(ii)	Explain, using electronic configuration, why iron is a transition element.
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[1]
[Total 2 marks]
 
3.	A moss killer contains iron(II) sulphate.
	Some of the iron(II) sulphate gets oxidised to form iron(III) sulphate. During the oxidation iron(II) ions, Fe2+, react with oxygen, O2, and hydrogen ions to make water and iron(III) ions, Fe3+.
(a)	Complete the electronic configuration for Fe3+ and use it to explain why iron is a transition element.
Fe3+:1s22s22p6 ................................................................................................
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[2]
 
(b)	State two typical properties of compounds of a transition element.
1 .....................................................................................................................
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[2]
(c)	Describe how aqueous sodium hydroxide can be used to distinguish between aqueous iron(II) sulphate and aqueous iron(III) sulphate.
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[2]
(d)	Construct the equation for the oxidation of acidified iron(II) ions by oxygen.
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[2]
[Total 8 marks]

4.	Iron forms several complex ions in which the oxidation state of iron is +3.
	Excess aqueous sodium hydroxide is added to an aqueous solution containing Fe3+(aq).
(i)	Describe what you would see happen.
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[1]
(ii)	Write an ionic equation, including state symbols, for the reaction that takes place.
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[2]
[Total 3 marks]
 
5.	The compound FeSO4.7H2O can be used to kill moss in grass. Iron(II) ions in a solution of FeSO4.7H2O are slowly oxidised to form iron(III) ions.
	Describe a test to show the presence of iron(III) ions in a solution of FeSO4.7H2O.
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[Total 1 mark]

6.	Iron forms several complex ions in which the oxidation state of iron is +3.
	One of these complex ions is [Fe(CN)6]3–. This is called the hexacyanoferrate(III) ion. In the hexacyanoferrate(III) ion the cyanide ions, CN–, act as ligands.
(i)	Suggest why a cyanide ion can act as a ligand.
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[1]
(ii)	Draw the expected shape for the complex ion [Fe(CN)6]3–. Include bond angles and the name of the shape.

[2]
[Total 3 marks]

 7.	Cobalt readily forms complex ions in which the cobalt has an oxidation state of +2.
	One complex ion of cobalt is the hexaaquocobalt(II) ion [Co(H2O)6]2+.
(i)	What is the co-ordination number of Co2+ in this complex ion?
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[1]
(ii)	Water is acting as a ligand. Explain the meaning of the term ligand.
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[2]
[Total 3 marks]

8.	Ammonia is a simple molecule. The H—N—H bond angle in an isolated ammonia molecule is 107°.
The diagram shows part of the [Cu(NH3)4(H2O)2]2+ ion and the H—N—H bond angle in the ammonia ligand.
		
	Explain why the H—N—H bond angle in the ammonia ligand is 109.5° rather than 107°.
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[Total 3 marks]
 
9.	Water is a simple molecule. The H—O—H bond angle in an isolated water molecule is 104.5°.
	The diagram shows part of the [Cu(H2O)6]2+ ion and the H—O—H bond angle in the water ligand.
		
	Explain why the H—O—H bond angle in the water ligand is 107° rather than 104.5°.
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[Total 3 marks]

10.	Artists between the 13th and the 19th Centuries used a green pigment called verdigris. The artists made the pigment by hanging copper foil over boiling vinegar.
	A sample of verdigris has the formula [(CH3COO)2Cu]2.Cu(OH)2.xH2O.
Analysis of the sample shows that it contains 16.3% water by mass.
Calculate the value of x in the formula.

answer ...................................................
[Total 3 marks]

11.	In this question, one mark is available for the quality of use and organisation of scientific terms.
	Copper and iron are typical transition elements. One of the characteristic properties of a transition element is that it can form complex ions.
•	Explain in terms of electronic configuration why copper is a transition element.
•	Give an example of a complex ion that contains copper. Draw the three dimensional shape of the ion and describe the bonding within this complex ion.
•	Transition elements show typical metallic properties. Describe three other typical properties of transition elements. Illustrate each property using copper or iron or their compounds.

[11]
Quality of Written Communication [1]
[Total 12 marks]

12.	Dilute aqueous copper(II) sulphate contains [Cu(H2O)6]2+ ions.
(a)	Concentrated hydrochloric acid is added drop by drop to a small volume of dilute aqueous copper(II) sulphate. The equation for the reaction taking place is as follows.
[Cu(H2O)6]2+(aq) + 4Cl–(aq)  [CuCl4]2–(aq) + 6H2O(l)
(i)	Describe the observations that would be made during the addition of the concentrated hydrochloric acid.
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[1]
(ii)	Describe the bonding within the complex ion, [CuCl4]2–.
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[2]
 (b)	Concentrated aqueous ammonia is added drop by drop to aqueous copper(II) sulphate until present in excess. Two reactions take place, one after the other, to produce the complex ion [Cu(NH3)4(H2O)2]2+(aq).
	Describe the observations that would be made during the addition of concentrated aqueous ammonia.
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[2]
[Total 5 marks]

13.	The Co2+ ion can form complexes with two different co-ordination numbers.
(a)	What is meant by the co-ordination number of a complex ion?
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[1]

(b)	The following equilibrium is readily established.
		[Co(H2O)6]2+ + 4Cl–  [CoCl4]2– + 6H2O
(i)	In the boxes below, draw the shape of each complex ion.
[Co(H2O)6]2+		[CoCl4]2–	
[2]
(ii)	What colour change would you expect to see when an excess of Cl– is added to [Co(H2O)6]2+?
from ............................................... to ..................................................
[2]
(iii)	Describe how you would move the position of this equilibrium to the left.
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[1]
[Total 6 marks]
 
14.	The ethanedioate ion, C2O42–, can act as a bidentate ligand when it forms complex ions with a transition metal ion. The structure of the ethanedioate ion is shown below.
		
(a)	What do you understand by the term bidentate ligand?
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[2]

(b)	The ethanedioate ion readily forms an octahedral complex ion with Cr3+.
	Show the structure and charge of this complex ion.

[3]
[Total 5 marks]
 
15.	The edta4– ion forms complex ions with Ni2+(aq).
(a)	Complete the electronic configuration of the Ni2+ ion.
Is22s22p6 ........................................................................................................
[1]
(b)	The edta4– ion has the following structure.

(i)	Put a ring around two different types of atom in the edta4– ion that are capable of forming a dative covalent bond with the Ni2+ ion.
[2]
(ii)	What feature of these atoms allows them to form a bond with Ni2+?
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[1]
[Total 4 marks]

16.	Stereoisomerism is very common in transition metal complexes. Some complexes have found an important use in the treatment of cancer.
(i)	Name a transition metal complex used in the treatment of cancer.
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[1]
(ii)	Describe how this complex helps in the treatment of cancer.
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[2]
[Total 3 marks]
 
17.	(a)	Co2+ forms the complex [Co(NH3)4Cl2]. This complex exists as two stereoisomers.
(i)	Draw diagrams to show the two isomeric forms of this complex.

[2]
(ii)	What type of stereoisomerism is shown by this complex?
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[1]
(b)	Cobalt also forms a complex with the formula [Co(H2NCH2CH2NH2)2Cl2]. This complex shows the same kind of isomerism as [Co(NH3)4Cl2] but it also shows a different type of stereoisomerism.
	Draw diagrams to show the two isomers of this different type of stereoisomerism.

[2]
[Total 5 marks]

18.	(a)	A common ligand which combines with a number of transition metal ions is ethane-1,2-diamine, H2NCH2CH2NH2. This is a bidentate ligand.
	Explain the meaning of the term bidentate.
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[1]
 (b)	The complex [CoCl2(H2NCH2CH2NH2)2] is a neutral molecule. It shows two types of stereoisomerism. Use this molecule to explain what you understand by the term stereoisomerism. Your answer should include diagrams to show clearly the structures of the different isomers in both types of stereoisomerism.

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[7]
[Total 8 marks]

19.	Platinum forms complexes with a co-ordination number of 4.
(a)	(i)	Explain the term co-ordination number.
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[1]
(ii)	State the shape of these platinum complexes.
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[1]
 (b)	The tetrachloroplatinate(II) ion readily undergoes the following reaction.
		[PtCl4]x + 2NH3  [Pt(NH3)2Cl2]y + 2Cl–
(i)	What type of reaction is this?
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[1]
(ii)	Suggest values for x and y in the equation.
		x = ……………
		y = ……………
[2]

(c)	The complex [Pt(NH3)2Cl2]y exists in two isomeric forms.
(i)	Draw diagrams to show the structure of these isomers.
		
[2]
(ii)	What type of isomerism is this?
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[1]
(iii)	One of the isomers of [Pt(NH3)2Cl2]y is an important drug used in the treatment of cancer.
	How does this drug help in the treatment of cancer?
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[2]
[Total 10 marks]

20.	Ruthenium (Ru) is a metal in the second transition series. It forms complex ions with the following formulae.
A	= [Ru(H2O)6]3+
B	= [Ru(H2O)5Cl]2+
C	= [Ru(H2O)4Cl2]+
(a)	(i)	What is the oxidation number of ruthenium in B?
oxidation number of ruthenium = .........................................................
[1]
(ii)	One of the complex ions, A, B or C, shows stereoisomerism.
	Draw diagrams to show the structures of the two isomers.

[2]
(iii)	Name this type of stereoisomerism.
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[1]
(b)	The complex ion [Ru(H2O)6]3+ can be converted into [Ru(H2O)5Cl]2+.
(i)	Suggest a suitable reagent for this conversion.
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[1]
(ii)	What type of reaction is this?
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[1]
[Total 6 marks]

21.	This question looks at the chemistry of transition elements.
(a)	(i)	Explain what is meant by the terms transition element, complex ion and ligand,
(ii)	Discuss, with examples, equations and observations, the typical reactions of transition elements.
	In your answer you should make clear how any observations provide evidence for the type of reaction discussed.
[11]

(b)	Describe, using suitable examples and diagrams, the different shapes and stereoisomerism shown by complex ions.
	In your answer you should make clear how your diagrams illustrate the type of stereoisomerism involved.

[9]
[Total 20 marks]