Q1.
Consider the following reaction scheme that starts from aqueous [Cu(H2O)6]2+ ions.
 
green-blue precipitate                                 
For each of the reactions 1 to 4, identify a suitable reagent, give the formula of the copper-containing species formed and write an equation for the reaction.
(a)     Reaction 1
Reagent ___________________________________________________________
Copper-containing species _____________________________________________
Equation ___________________________________________________________
(3)
(b)     Reaction 2
Reagent ___________________________________________________________
Copper-containing species _____________________________________________
Equation ___________________________________________________________
(3)
 (c)     Reaction 4
Reagent ___________________________________________________________
Copper-containing species _____________________________________________
Equation ___________________________________________________________
(3)
(Total 9 marks)

Q2.
The scheme below shows some reactions of copper(II) ions in aqueous solution.
W, X, Y and Z are all copper-containing species.
 
(a)     Identify ion W. Describe its appearance and write an equation for its formation from [Cu(H2O)6]2+(aq) ions.
Ion W ______________________________________________________________
Appearance _________________________________________________________
Equation ___________________________________________________________
(3)
(b)     Identify compound X. Describe its appearance and write an equation for its formation from [Cu(H2O)6]2+(aq) ions.
Compound X ________________________________________________________
Appearance _________________________________________________________
Equation ___________________________________________________________
(3)
(c)     Identify ion Y. Describe its appearance and write an equation for its formation from X.
Ion Y ______________________________________________________________
Appearance _________________________________________________________
Equation ___________________________________________________________

 (d)     Copper metal can be extracted from a dilute aqueous solution containing copper(II) ions using scrap iron.
(i)      Write an equation for this reaction and give the colours of the initial and final aqueous solutions.
Equation ______________________________________________________
Initial colour ____________________________________________________
Final colour ____________________________________________________
(3)
(ii)     This method of copper extraction uses scrap iron. Give two other reasons why this method of copper extraction is more environmentally friendly than reduction of copper oxide by carbon.
Reason 1 ______________________________________________________
Reason 2 ______________________________________________________
(2)
(Total 14 marks)

Mark schemes
Q1.
(a)    Reaction 1
General principles in marking this question
Square brackets are not essential
Penalise charges on individual ligands rather than on the whole complex
Reagent and species can be extracted from the equation
Ignore conditions such as dilute, concentrated, excess
Reagent must be a compound NOT just an ion
Equations must start from [Cu(H2O)6 ]2+ except in part (b)
Mark reagent, species and equation independently
ammonia (NH3) (solution) / NaOH
1
[Cu(H2O)6]2+ + 2NH3 → [Cu(H2O)4(OH)2] + 2NH4+ /
[Cu(H2O)6]2+ + 2OH- → [Cu(H2O)4(OH)2] + 2H2O
Do not allow OH– for reagent
Product 1, balanced equation 1
Allow either equation for ammonia
2
(b)    Reaction 2
Ammonia (conc / xs)
1
[Cu(H2O)4(OH)2] + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 2H2O + 2OH−
Product 1, balanced equation 1
Note that the equation must start from the hydroxide [Cu(H2O)4(OH)2]
2
 (c)    Reaction 4
HCl (conc / xs) / NaCl
Allow any identified soluble chloride
1
[Cu(H2O)6]2+ + 4Cl- → [CuCl4]2- + 6H2O
Product 1, balanced equation 1
2
[9]
Q2.
(a)     W is CuCl42–
1
Yellow-green/yellow/green
Not necessary to indicate solution
Do not allow precipitate/solid
1
[Cu(H2O)6]2+ + 4Cl– → CuCl42– + 6H2O
Allow + 4HCl → 4H+
1
(b)     X is Cu(H2O)4(OH)2
Allow Cu(OH)2/copper hydroxide
1
Blue precipitate/solid
Ignore shades
1
[Cu(H2O)6]2+ + 2NH3 → Cu(H2O)4(OH)2 + 2NH4+
Allow any balanced equation/equations leading to this hydroxide or Cu(OH)2
But must use ammonia
1
(c)     Y is [Cu(NH3)4(H2O)2]2+
1
Deep/dark/royal blue solution
QoL
1
Cu(H2O)4(OH)2 + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH–
Accept equation for formation from Cu(OH)2
1

(d)     (i)      Cu2+(aq) + Fe(s) → Cu(s) + Fe2+(aq)
Allow hydrated ions
State symbols not essential but penalise if wrong
1
Blue
Do not allow description of solids
1
Green
Allow yellow/(red-)brown/orange
1
(ii)     Any two correct points about copper extraction from two
of these three categories:
Any relevant mention of lower energy consumption
Do not allow reference to electricity alone or to temperature alone.
Any relevant mention of benefits of less mining (of copper ore)
Allow avoids depletion of (copper ore) resources
Less release of CO2 (or CO) into the atmosphere
Not just greenhouse gases. Must mention CO2 or CO