plumiFormation of coloured ions: AQA A‑Level Chemistry questions
AQA A-Level Chemistry past-paper questions on 3.2.5.4 Formation of coloured ions, 2008–2025, with mark schemes and examiner’s reports where available.
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Q03.4
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All 30 questions on Formation of coloured ions, as a list
- June 2025, Paper 1, Q03.4 (6 marks): When a solution containing [Cu(H2O)6]2+ ions reacts with an excess of concentrated hydrochloric acid, a ligand exchange reaction occurs. [Cu(H2O)6]2+(aq) + 4 Cl
- June 2024, Paper 3, Q05.1 (6 marks): Some complexes containing transition metal ions are coloured. • Explain why some complexes containing transition metal ions are coloured. • List the factors tha
- June 2024, Paper 3, Q05.2 (3 marks): Figure 5 shows the visible spectrum of [Cu(H2O)6]2+ Figure 5 Use the wavelength at the peak of the curve in Figure 5 to calculate the change in energy, in J, of
- June 2023, Paper 1, Q07.4 (1 mark): State why the concentration of aluminium sulfate solution can not be determined by colorimetry. [1 mark]
- June 2022, Paper 1, Q07.1 (2 marks): Explain why aqueous solutions containing [CuCl4] 2– ions are yellow. [2 marks]
- June 2022, Paper 1, Q07.2 (2 marks): When a d electron moves from the ground state to the excited state in a copper complex, the energy change is 3.98 x 10–19 J The Planck constant, h = 6.63 × 10−3
- June 2022, Paper 1, Q07.3 (3 marks): State three ways in which a transition metal complex can be changed to alter its colour. [3 marks] 1 2 3
- November 2021, Paper 3, Q07 (1 mark): Which does not involve the absorption of ultraviolet radiation or visible light? [1 mark] A The blue appearance of copper(II) sulfate solution in daylight. B Th
- November 2020, Paper 3, Q03.1 (3 marks): Explain why complexes formed from transition metal ions are coloured. [3 marks]
- November 2020, Paper 3, Q03.2 (3 marks): Calculate the energy, in J, gained by each excited electron in the absorption at 490 nm Speed of light, c = 3.00 x 108 m s–1 Planck constant, h = 6.63 x 10–34 J
- November 2020, Paper 3, Q03.3 (3 marks): Describe how a calibration graph is produced and used to find the concentration of the iron(III) complex. [3 marks]
- November 2020, Paper 3, Q03.4 (2 marks): The concentration of iron(III) in the solution is 4.66 x 10–3 mol dm–3 Calculate the mass, in mg, of iron in the tablet used to make the 250 cm3 of solution. [2
- June 2019, Paper 1, Q06.5 (2 marks): Copper(I) iodide is a white solid. Explain why copper(I) iodide is white. [2 marks]
- June 2017, Paper 1, Q07.6 (2 marks): Explain why colorimetry cannot be used to determine the concentration of solutions containing [CuCl2]− In your answer refer to the electron configuration of the
- June 2017, Paper 3, Q31 (1 mark): A solution absorbs light with wavelengths corresponding to red, yellow and green light. Which ion is most likely to be in the solution? [1 mark] A Cr2O7 2−(aq)
- June 2016, CHEM5 (old spec), Q9(e) (3 marks): A solution of KMnO4 has an unknown concentration. Describe briefly how colorimetry can be used to determine the concentration of this solution. [3 marks]
- June 2013, CHEM5 (old spec), Q6(a) (2 marks): Give the equation that relates the energy change ΔE to the Planck constant h and the frequency of the visible light v. Use this equation and the information in
- June 2013, CHEM5 (old spec), Q6(b) (2 marks): Explain why this electron transition causes a solution containing the transition metal ion to be coloured.
- June 2013, CHEM5 (old spec), Q6(c) (2 marks): The energy change shown in the diagram represents the energy of red light and leads to a solution that appears blue. Blue light has a higher frequency than red
- June 2013, CHEM5 (old spec), Q6(d) (3 marks): State three different features of transition metal complexes that cause a change in the value of ΔE, the energy change between the ground state and the excited
- January 2013, CHEM5 (old spec), Q8(c) (3 marks): The complex ion formed in aqueous solution between cobalt(II) ions and chloride ions is a different colour from the [Co(H2O)6]2+ ion. Explain why these complex
- June 2012, CHEM5 (old spec), Q7(c) (3 marks): When an aqueous solution containing [Cr(H2O)6]3+ ions is warmed in the presence of Cl– ions, [Cr(H2O)5Cl]2+ ions are formed and the colour of the solution chang
- January 2012, CHEM5 (old spec), Q2(e) (2 marks): Pure ice can look pale blue when illuminated by white light. Suggest an explanation for this observation.
- January 2012, CHEM5 (old spec), Q6(b) (2 marks): By considering the properties of the reactants and products, state why it is possible to use a spectrometer to measure the concentration of the manganate(VII) i
- June 2011, CHEM5 (old spec), Q7(a)(i) (3 marks): With reference to electrons, explain why aqueous copper(II) ions are blue.
- June 2011, CHEM5 (old spec), Q7(a)(ii) (3 marks): By reference to aqueous copper(II) ions, state the meaning of each of the three terms in the equation ΔE= hv.
- June 2010, CHEM5 (old spec), Q1(e) (2 marks): Calcium fluoride crystals absorb ultra-violet light. Some of the energy gained is given out as visible light. The name of this process, fluorescence, comes from
- June 2010, CHEM5 (old spec), Q4(c) (3 marks): In terms of electrons, explain why an aqueous solution of cobalt(II) sulfate has a red colour.
- January 2010, CHEM5 (old spec), Q9(a) (5 marks): State the electron configuration of a Ti(III) ion and that of a Ti(IV) ion. Explain, in terms of electron configurations and electron transitions, why Ti(III) c
- January 2010, CHEM5 (old spec), Q9(c)(i) (2 marks): Give two reasons why the use of a spectrometer is the most appropriate method for measuring the concentration of the coloured ions in this experiment.
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