Transition Metals & Complexes (Edexcel International A Level Chemistry)

A series of reactions with iron and iron complexes was carried out.

Reaction 1	A sample of iron was heated with hydrochloric acid and a pale green hydrated salt A with molar mass 198.8 g mol–1 was crystallised from the solution.
Reaction 2	Salt A was dissolved in water forming a pale green solution containing complex ion B. On addition of excess aqueous potassium cyanide, KCN, the solution turned yellow due to the formation of complex ion C.
Reaction 3	Chlorine gas was bubbled through the solution containing complex ion C forming a red solution of complex ion D. Salt E, the potassium salt of complex ion D, was then crystallised from the solution.

Deduce the formula of the hydrated salt A.
You must show your working.

Give the formula of complex ion B.

Complex ion C has six cyanide ligands.
Draw the structure of C, clearly showing its three‐dimensional shape.

The percentage composition by mass of salt E is

K = 35.6%   Fe = 17.0%   C = 21.9%   N = 25.5%

Calculate the empirical formula of salt E.

Write the ionic equation for the reaction of complex ion C with chlorine to form complex ion D.

Complete the table, using as appropriate, to identify the type of each reaction.

	Neutralisation	Ligand exchange	Redox
Reaction 2
Reaction 3