Preparation of Copper(I) Chloride, CuCl
Goal: To prepare copper(I) chloride by reducing
copper(II) chloride with sulfite ions in the presence of chloride
Objectives: At the end of this session students
should be able to:
- Isolate and store inorganic compounds with unstable oxidation
- Discuss the relative stability of Cu(I) and Cu(II) ions
- Predict the structures of ionic salts like Cu(I) chloride and
Cu(II) chloride from radius ratio rules
- Suggest why radius ratio rules sometimes fail to accurately
predict the structure of ionic crystals.
Copper can exist as Cu(I), Cu(II) which is most common and
Cu(III) which is rare. The relative stabilities of each oxidation
state depend on the nature of ligands and anions as well as the
nature of the solvent medium. In the experiment below the
copper(I) ions once formed, react with chloride ions to form the
insoluble copper(I) chloride.
The relevant redox potentials are:
Cu+ + e- ↔ Cu(s) E° = 0.52 V
Cu2+ + e- ↔ Cu+ E°
= 0.15 V
Cu2+ + 2e- ↔ Cu(s) E° = 0.34
Hence Cu(s) + Cu2+ ↔ 2Cu+ E° = -0.37 V
WARNING! Glacial acetic acid is a
dangerous liquid and must be used in a fume cupboard.
Prepare three solutions:
Add slowly, with constant stirring, the sodium sulfite solution
to the copper(II) chloride solution. Dilute the suspension of
copper(I) chloride so formed with about half the sulfurous acid
solution, allow the precipitate to settle, and decant most of the
- (a) dissolve sodium sulfite (2.5 g) in 13 cm3 of
- (b) dissolve copper(II) chloride dihydrate (3.3 g) in 7
cm3 of water,
- (c) prepare a sulfurous acid solution by dissolving sodium
sulfite (0.3 g) in 250 cm3 of water and add 3
cm3 of 2 M hydrochloric acid,
Filter the solid by suction on a Buchner funnel or sintered glass
crucible (fumehood) and wash it into the funnel by means of the
sulfurous acid solution. Take care that the copper(I) chloride
is always covered by a layer of solution. Finally, wash the
product with 5 cm3 of glacial acetic acid and 10
cm3 of ethanol and dry it in air, or in a vacuum
desiccator. Determine and record the yield.
Immediately show the product to a demonstrator for grading. Store
in a stoppered bottle and label with your name, formula of
compound and yield.
Write a balanced chemical equation for the preparation and
calculate the % yield based on the quantity of copper(II)
chloride hydrate used.
Note that both CuCl and CuCl2 have crystalline ionic
lattice structures. The structure of an ionic salt depends on the
relative sizes of the ions that form the solid. The relative
sizes of these ions is given by the radius ratio, which is the
radius of the positive ion divided by the radius of the negative
If the assumptions of an ionic model hold then the structures of
the ionic crystal can be rationalized based on the radius ratio
rules shown below:
||Holes in Which Cations Pack
|0.155 - 0.225
|0.225 - 0.414
|0.414 - 0.732
|0.732 - 1
Note: The lower limit in each range is the ideal ratio and is
known as the LIMITING RADIUS RATIO. The text-book and
this link to the Univ of Sydney
might be useful for additional information on the calculation of the
Below 400 °C CuCl has the zinc
blende structure (ccp) but above this temperature it converts
to the wurtzite structure
(hcp). CuCl2 has a CdCl2 type structure
Copyright © 2009-2013 by The Department
of Chemistry UWI, Jamaica, all rights reserved.
Created and maintained by Prof. Robert J.
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.
Created Nov 2009. Links checked and/or last
modified 30th October 2014.