Q1.
 (b)     An excess of concentrated hydrochloric acid is added to separate aqueous solutions containing [Cu(H2O)6]2+ and [Co(H2O)6]2+.
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(4)
(c)     An excess of dilute aqueous sodium hydroxide is added to separate aqueous solutions containing [Fe(H2O)6]2+ and [Cr(H2O)6]3+.
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(4)
Q2.
This question is about test-tube reactions of some ions in aqueous solution.
For each reaction in parts (a) to (d), state the colour of the original solution.
State what you would observe after the named reagent has been added to the solution.
In each case, write an equation for the reaction that occurs.
(b)     Sodium hydroxide solution is added to a solution containing [Fe(H2O)6]3+ ions.
Colour of original solution ______________________________________________
Observation after reagent has been added ________________________________
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Equation
 
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(3)
(c)     An excess of ammonia solution is added to a solution containing [Cu(H2O)6]2+ ions.
Colour of original solution ______________________________________________
Observation after an excess of reagent has been added ______________________
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Equation
 
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(3)
Q3.
Aqueous metal ions can be identified by test-tube reactions.
          For each of the following, describe what you would observe.
          Write an equation or equations for any reactions that occur.
 (c)     The addition of dilute aqueous ammonia, dropwise until in excess, to a solution containing [Cu(H2O)6]2+(aq) ions.
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(4)
(d)     The addition of concentrated hydrochloric acid, dropwise until in excess, to a solution containing [Cu(H2O)6]2+(aq) ions.
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(2)
Q4.
(a)     State what is meant by each of the following terms.
(i)      Ligand ________________________________________________________
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(ii)     Complex ion ___________________________________________________
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(iii)     Co-ordination number ____________________________________________
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(3)
 (c)     An aqueous solution of iron(II) sulphate is a pale-green colour. When aqueous sodium hydroxide is added to this solution a green precipitate is formed. On standing in air, the green precipitate slowly turns brown.
(i)      Give the formula of the complex ion responsible for the pale-green colour.
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(ii)     Give the formula of the green precipitate.
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(iii)     Suggest an explanation for the change in the colour of the precipitate.
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(4)
Q5.
Consider the reaction scheme below and answer the questions which follow. 
 
(a)     A redox reaction occurs when Cu(NO3)2 is decomposed by heat. Deduce the oxidation state of nitrogen in Cu(NO3)2 and in NO2 and identify the product formed by oxidation in this decomposition.
Oxidation state of nitrogen in Cu(NO3)2 ___________________________________
Oxidation state of nitrogen in NO2 _______________________________________
Oxidation product ____________________________________________________
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(3)
(b)     Identify and state the shape of the copper-containing species present in solution A.
Copper-containing species _____________________________________________
Shape _____________________________________________________________
(2)
(c)     (i)      Identify the pale blue precipitate B and write an equation, or equations, to show how B is formed from the copper-containing species in solution A.
Identity of precipitate B ___________________________________________
Equation(s) ____________________________________________________
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(ii)     In what way does the NH3 behave as a Brønsted–Lowry base?
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(3)
(d)     (i)      Identify the copper-containing species present in solution C. State the colour of this copper-containing species and write an equation for its formation from 
precipitate B.
Identity ________________________________________________________
Colour ________________________________________________________
Equation ______________________________________________________
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(ii)     In what way does the NH3 behave as a Lewis base?
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(4)
(e)     Identify the copper-containing species present in solution D. State the colour and shape of this copper-containing species.
Identity ____________________________________________________________
Colour _____________________________________________________________
Shape _____________________________________________________________
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(3)
(f)      The oxidation state of copper in [CuCl4]3– is +1.
(i)      Give the electron arrangement of a Cu+ ion.
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(ii)     Deduce the role of copper metal in the formation of [CuCl4]3– from the copper-containing species in solution D.
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(2)
(Total 17 marks)

Mark schemes
Q1.
 (b)     Copper(II): blue (solution) gives a green / yellow solution OR blue solution (turns) to green / yellow / olive green
Apply list principle throughout if extra colours and / or extra observations given. Ignore state symbols in equations.
1
[Cu(H2O)6]2+ + 4Cl− → [CuCl4]2− + 6H2O
Allow equations with HCl
1
Cobalt(II): pink (solution) gives a blue solution OR pink solution turns blue
1
[Co(H2O)6]2+ + 4Cl− → [CoCl4]2− + 6H2O
1
(c)     Iron(II): green (solution) gives a green precipitate
Apply list principle throughout if extra colours and / or extra observations given. Ignore state symbols in equations.
1
[Fe(H2O)6]2+ + 2OH− → Fe(H2O)4(OH)2 + 2H2O
Allow equations with NaOH
1
Chromium(III): green / ruby / purple / violet / red-violet (solution) gives a green solution OR green / ruby / purple / violet / red-violet solution turns green
Ignore green ppt.
1
[Cr(H2O)6]3+ + 6OH− → [Cr(OH)6]3− + 6H2O
Allow also with 4 or 5 OH balanced with 2 or 1 waters.
Also allow two correct equations showing Cr(H2O)3(OH)3 as intermediate.
1
Q2.
(b)     Yellow / purple (solution)
Allow orange / brown (solution)
1
Brown precipitate / solid
1
[Fe(H2O)6]3+ + 3OH− → Fe(H2O)3(OH)3 + 3H2O
1
(c)     Blue (solution)
Allow pale blue
1
Dark / deep blue solution
Ignore any reference to blue ppt
1
[Cu(H2O)6]2+  + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O
Can be in two equations
1
Q3.

(c)     Blue ppt/solid
1
(Dissolves to give a) deep blue solution
Only award M2 if M1 given or initial ppt mentioned
1
[Cu(H2O)6]2+ + 2NH3 → Cu(H2O)4(OH)2 + 2NH4+
Allow [Cu(H2O)6]2+ + 2NH3 → Cu(OH)2 + 2NH4+ + 4H2O
Allow two equations: NH3 + H2O → NH4+ + OH–
then [Cu(H2O)6]2+ + 2OH– → Cu(OH)2 + 4H2O etc
1
Cu(H2O)4(OH)2 + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 2OH– + 2H2O
Allow [Cu(H2O)6]2+ + 4NH3 → [Cu(H2O)2(NH3)4]2+ + 4H2O
1
(d)     Green/yellow solution
1
[Cu(H2O)6]2+ + 4Cl– → [CuCl4]2– + 6H2O
1
Q4.
(a)     (i)      An atom, ion or molecule which can donate a lone electron pair
1
(ii)     A central metal ion/species surrounded by co-ordinately
bonded ligands or ion in which co-ordination number
exceeds oxidation state
1
(iii)     The number of co-ordinate bonds formed to a central metal ion
or number of electron pairs donated or donor atoms
1

(c)     (i)      [Fe(H2O)6]2+
1
(ii)     Fe(OH)2 or Fe(OH)2(H2O)x where x = 0 to 4
1
(iii)     Fe2+ is oxidised to Fe3+ or Fe(OH)3
1
By oxygen in the air
1
Q5.
(a)     oxidation state of N in Cu(NO3)2:   +5;
1
oxidation state of N in NO2:           +4;
1
oxidation product: oxygen;
1
(b)     copper-containing species:        [Cu(H2O)6]2+;
1
shape:  octahedral;
1
(c)     (i)      precipitate B:   Cu(H2O)4(OH)2 or Cu(OH)2 or name;
1
equation:         [Cu(H2O)6]2+ + 2NH3 → Cu(H2O)4(OH)2 + 2NH4+
OR
                        NH3 + H2O → NH4+ + OH–
and
          [Cu(H2O)6]2+ + 2OH– → Cu(H2O)4(OH)2 + 2H2O;
1
(ii)     NH3 accepts a proton;
1
(d)     (i)      identity: [Cu(NH3)4(H2O)2]2+;
1
colour: deep blue;
1
equation:
Cu(H2O)4(OH)2 + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH–;
1
(ii)     NH3 is an electron pair donor;
1
(e)     identity:    [CuCl4]2–;
1
colour:      yellow-green;
1
shape:      tetrahedral;
1
(f)      (i)      Is2 2s2 2p6 3s2 3p6 3d10 ;
1
(ii)     role of Cu:    a reducing agent;
1
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