(12)1, 15

Adding concentrated HCl(aq) to CuSO4(aq) causes the colour of the solution to change from blue to green.

Which row best explains this observation?

Number ofd-electrons

around copper

Energy gap between the d-orbitals

A Changes ChangesB Changes Remains the sameC Remains the same ChangesD Remains the same Remains the same

(12)1, 17

The data below refers to a particular element.

Density 10.5gcm-3

First ionisation energy 730kJmol-1

Second ionisation energy 2070kJmol-1

Third ionisation energy 3360kJmol-1

Melting point 1235K

Where in the Periodic Table is this element most likely to be found?

A. Group IB. Group IIC. Group VIID. The transition elements

(12)1, 36

Which properties of transition elements are not shown by s-block elements such as calcium?

1. They have variable oxidation states.2. Their ions can act as oxidising agents in aqueous solution.3. Their ionic radii are less than their atomic radii.

(12)2, 3c [3 marks]

When concentrated hydrochloric acid is added to aqueous copper(II) chloride, the solution eventually becomes yellow. When water is added to this yellow solution, it becomes blue.

Suggest by means of ionic equations, an explanation for these observations.

(11)1, 1

Use of the Data Booklet is relevant to this question.

The sunlight-induced photolysis of water is being investigated as a useful source of the pollution-free fuel hydrogen.

2 H 2O →2 H 2+O2

It has been found that anatase, one of the three crystalline forms of the ionic compound TiO2, is a good catalyst for this reaction.

How many electrons are associated with each titanium ion in the anatase lattice?

A. 18B. 19C. 20D. 22

(11)3, 4c [6 marks]

The iron atoms in haemoglobin are in the oxidation state +2 and are in an octahedral environment. Each iron atom is surrounded by five nitrogen-containing ligands, and one oxygen-containing ligand, which is H2O in deoxyhaemoglobin and O2 in oxyhaemoglobin.

The following diagram shows how the d-orbitals are split in an octahedral environment.

(i) Use this diagram to outline the origin of the red colour of haemoglobin.

When the H2O ligand in haemoglobin is changed to an O2 ligand, the Fe2+ ion changes its electronic configuration from a “high spin” state to a “low spin” state.

In a “high spin” state, the electrons occupy all the d-orbitals singly, before starting to pair up in the lower energy d-orbitals.

In a “low spin” state, the lower energy d-orbitals are filled first, by pairing up if necessary before the higher energy d-orbitals are used.

(ii) Use diagrams like the one above to show the electronic distribution of a Fe 2+ ion in a high spin state, and in a low spin state.

(iii) Suggest why electrons usually prefer to occupy orbitals singly, rather than in pairs.

(iv) Using this explanation, together with the information given above concerning the spin states of deoxyhaemoglobin and the oxyhaemoglobin, state and explain which of the two haemoglobins will contain the larger energy gap, E, between its d-orbitals.

(10)1, 18

Which statement correctly defines a transition element?

A. Transition elements exhibit more than one oxidation state in their compounds.B. Transition elements form many coloured compounds.C. Transition elements have partially filled d orbitals.D. Transition elements or their compounds are widely used as catalysts.

(10)3, 5d [3 marks]

When concentrated hydrochloric acid is added to a solution containing Cu2+(aq), the colour changes to a pale yellow-green. No gas is evolved.

No such colour change occurs when concentrated sulfuric acid is added to Cu2+(aq).

Dilution of the yellow-green solution with water produces the original pale blue colour.

Suggest an explanation of these observations.

(09)1, 17

Use of the Data Booklet is relevant to this question.

The bar chart gives some information about the first ionisation energies of elements, numbered 1 to 4.

The elements are adjacent to each other in the Periodic Table with increasing proton number either across from left to right, or down a group.

What could these four elements be?

A. B, C, N, OB. Co, Ni, Cu, ZnC. Mg, Ca, Sr, BaD. Si, P, S, Cl

(09)2, 2

Mazak is an alloy of magnesium, aluminium, zinc and copper which is widely used to make die-cast toys.

Magnesium and aluminium are adjacent elements in the third Period of the Periodic Table; zinc and copper are next to each other in the first set of transition elements.

The densities of the four metals present in Mazak, in ascending numerical order, are given below.

Metal 1 Metal 2 Metal 3 Metal 4Density /gcm-3 1.74 2.70 7.13 8.94

a) Suggest which two of the metals, Mg, Al, Zn, and Cu, which are present in Mazak, are metals 3 and 4. [1 mark]

b) When finely powdered Mazak is shaken with cold dilute hydrochloric acid, three of the metals dissolve and one remains as a solid residue.Use the Data Booklet to identify this residue. Explain your answer. [2 marks]

c) Mazak can be completely dissolved in hot concentrated sulfuric acid. Sulfur dioxide is also formed.

i. In what way does sulfuric acid behave in this reaction? [1 mark]ii. Use the Data Booklet to construct an equation for the reaction of hot

concentrated sulfuric acid with zinc. [1 mark]d) When NaOH(aq) is added to separate solutions containing Mg2+(aq) and Al3+(aq), a

white precipitate is formed in each case. When an excess of NaOH(aq) is added, one of these precipitates dissolves.

i. Suggest the formula of the white precipitate that is soluble in an excess of NaOH(aq) [1 mark]

ii. Construct ionic equations forthe formation of this precipitate, [1 mark]and its subsequent dissolving. [1 mark]

Zinc has some properties that are similar to those of a Group II metal and some that are of those of a transition element.

e) Suggest why zinc shows some properties of Group II elements. [1 mark]f) Zinc nitrate and magnesium nitrate decompose when heated to give similar products.

i. Suggest an equation for the thermal decomposition of zinc nitrate. [1 mark]ii. The radius of the Zn2+ cation is 0.074nm. Use the Data Booklet to deduce

whether zinc nitrate will decompose at a higher or lower temperature than magnesium nitrate. Explain your answer. [1 mark]

g) When NH3(aq) is added to a solution containing Zn2+(aq), a white precipitate is formed which is soluble in an excess of the reagent.In these reactions, zinc behaves like a transition element. Suggest an ionic equation for each of these two reactions. [2 marks]

(08)2, 4

Copper is a typical transition element. It has more than one oxidation state and many of its compounds have colours in the blue-green-yellow part of the visible spectrum.

a) Complete the electronic configuration of copper atoms and copper(II) ions. [2 marks]Cu 1s2 2s2 2p6

Cu2+ 1s2 2s2 2p6

b) Aqueous copper(II) chloride, CuCl2, is a green-blue solution which gives the following reactions. In each case the precipitate initially formed is separated before being treated with NH3(aq).

i. State the formula of compound B. [1 mark]ii. What is the formula of the cation present in CuCl2(aq) and of the cation

present in C? [2 marks]

c) Aqueous CuCl2 also undergoes the following reactions.

D and E contain complex ions of copper and chlorine. F is a compound of copper and chlorine only.

When CuCl2(aq) is converted into D and into E, one mole of CuCl2 reacts exactly with two moles of HCl. In each case, no other compound is formed.

The oxidation number of copper in E is the same as in F.

i. Suggest balanced equations for the formation of D from CuCl2 and for the formation of E from CuCl2. [2 marks]

ii. Suggest the formula of the complex ion present in D and of the complex ion present in E. [1 mark]

iii. Which type of reaction occurs when D is formed from CuCl2(aq)? [1 mark]iv. Suggest the shape of the complex ion present in D? [1 mark]v. What is the oxidation number of copper in the complex ion in E? [1 mark]

d) The oxidation number of copper in compound F is the same as that in complex ion E.i. What type of reaction occurs when D is converted into F? [1 mark]

ii. Suggest a formula for compound F. [1 mark]

e) Under suitable conditions, CuCl2 can be converted into G which is pale green in colour. The composition of G by mass is Cu, 21.5%; F, 38.7%; K, 39.8%.

i. Use the data to calculate the empirical formula of G. [2 marks]ii. Suggest the oxidation state of copper in G.

f) E and F are both colourless. All other copper compounds mentioned are coloured.i. Explain why E and F are both colourless. [2 marks]

ii. Suggest an explanation for G being coloured. [2 marks]