CAIE A Level Chemistry 9701 · Chemistry of transition elements
An aqueous solution of cobalt(II) chloride contains the complex and is pink. When concentrated hydrochloric acid is added, the colour changes to blue as the tetrahedral complex is formed.
Compare the colours of these two cobalt complexes and explain the reason for the colour change.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.