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Edexcel IAL Chemistry 17.9 why some aqueous ions are colourless

A colourless ion often lacks the right transition: full d, empty d, no f electrons or an energy gap outside the visible region prevents visible absorption.

Syllabus
First assessment 2019
Course
Chemistry YCH11
Level
A2

Exam points

  • Explain colourless ions by full or empty d subshells preventing d-d transitions.
  • Use energy gaps outside the visible spectrum to justify a colourless ion.
  • Apply f-electron reasoning to colourless lanthanide aqua ions when needed.

17.9—Why there is a lack of colour in some aqueous ions and other complex ions question 1

[Maximum number: 3]

The diagram summarises some reactions of copper compounds.

Figure for Question 17.9—Why there is a lack of colour in some aqueous ions and other complex ions question 1 — Edexcel A-Level Chemistry A2

T and V are the same type of chemical species.

Explain why T is coloured while V is colourless. A detailed explanation of the fact that T is coloured is not required.
(3)

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