Question 1
Paper 2Hard8 marksCobalt(II) occurs in differently coloured complexes. A student records the appearance and wavelength of maximum absorption for two solutions.
| Complex in solution | Appearance | Wavelength of maximum absorption / nm |
|---|---|---|
| [Co(H₂O)₆]²⁺ | pink | 535 |
| [CoCl₄]²⁻ in chloride-rich solution | blue | 610 |
(a)[1]
State what happens to an electron when visible light is absorbed by a transition-element complex.
(b)[2]
Use the colour wheel in the data booklet to identify the colour of light absorbed by each solution.
(c)[5]
A student argues: “Because the solution looks blue, its complex absorbs higher-frequency light than the pink solution.” Assess this claim quantitatively, using the data.