Transition Metal Reactions (Edexcel International A Level Chemistry): Exam Questions

The diagram summarises some reactions of copper compounds.

Identify, by name (including the oxidation state) or formula, the species in the sequence that contain copper.

P ......................................................
Q ......................................................
R ......................................................
S ......................................................
T ......................................................
V ......................................................
W ......................................................

T and V are the same type of chemical species.

i) Name this type of chemical species.

(1)

ii) Explain why T is coloured while V is colourless.

A detailed explanation of the fact that T is coloured is not required.

(3)

iii) Suggest an explanation for the change of V into T on shaking.

(2)

The reaction between copper(I) iodide and sulfuric acid is a disproportionation.

i) Write the ionic equation for this disproportionation reaction.

State symbols are not required.

(1)

ii) Show that the reaction in (c)(i) is thermodynamically feasible.

Use the standard electrode potentials of the relevant half-cells from the Data Booklet.

(2)

The rare mineral mitscherlichite has the chemical formula K₂CuCl₄⦁nH₂O.

4.26 g of mitscherlichite was dissolved in distilled water and the solution made up to 250.0 cm³. Excess potassium iodide solution was added to a 25.0 cm³ portion of this solution and the iodine formed was titrated against a solution of sodium thiosulfate with a concentration of 0.0500 mol dm⁻³.

This procedure was repeated until concordant results were obtained. The mean accurate titre was 26.65 cm³. The equations for the reactions are

Calculate the value of n, the number of moles of water of crystallisation per mole of mitscherlichite.