The Amateur Chemist

Synthesis of Copper (II) Chloride

Copper (II) chloride is the chemical compound with the formula CuCl2. This is a light brown solid, which slowly absorbs moisture to form a blue-green dihydrate. The copper (II) chlorides are some of the most common copper (II) compounds, after copper sulfate.

Formula: CuCl2 

Molar mass: 134.45 g/mol 

Melting point: 498° C (928.4° F) 

Density: 3.39 g/cm³ 

Boiling point: 993° C (1,819° F)
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SOME STOICHIOMETRY


CuCO3  +  2HCl  ---->  CuCl2  +  CO2 + H2O

123.555 g/mol + 36.46 g/mol ----> 134.45 g/mol  + 44.01 g/mol + 18.0153 g/mol

Some simple stoichiometry can show us how much carbonate and acid to use and what out yield will be.  In this experiment we will use 31.45% HCl since that is commonly found at many hardware stores. Since 36.46 g/mol is for pure 100% HCl we need to divide this by .3145.  This yields 115.93 g/mol.  Lets say I want 50 grams total of Copper (II) Chloride. I divide it's molar equation by 50 to get that ratio.  134.45/50 = 2.689.  Now, I divide everything else by that ratio as well to keep the reaction balanced.  Finally, since 1 mole of CuCO3 reacts with 2 moles of HCL, we need to multiply the HCl part by 2.  This means that... 45.948 g  + 86.225 g ---> 50 g  + 16.3666 g + 6.699 g .   This reaction actually forms H2CO3, or carbonic acid, but this quickly decomposes into CO2 and H2O so we don't really count it.  This 50 grams of Copper Chloride is actually anhydrous, but when it combines with water, it forms a dihydrate, or CuCl2 . 2H2O. This means that the dried Copper Chloride will weigh more than 50 grams. It should weigh about 13.4 grams extra bringing it to a total of 63.4 grams.  There may be some other complex copper chloride + water molecules in their as well, so it is hard to predict the true yield. That is what experimentation is for.


Start with some copper (II) carbonate which will be made in an upcoming experiment. According to the above equation, add around 46 grams. Add this into the hydrochloric (around 86 grams) acid until it stops fizzing. Add only a gram or two at once and stir/swirl in between additions.  It will foam quite a bit, so let it settle in between additions unless you want acid everywhere. Once it stops fizzing, let it sit in a dry place to evaporate. If you can, spread it out onto something larger so there it is only a mm or two thick as this will greatly aid the drying process.  Once the copper chloride is dry, scoop it into an airtight container. Pure Copper (II) Chloride Dihydrate will be a light blue color. Since we made ours using hydrochloric acid, the final crystals will be acidic. This will make them be a light green color instead. For most reactions, this acidic impurity will not matter. There are other ways to make Copper II Chloride adding salt (sodium chloride) to copper sulfate, but I have always liked this method the best.


If you need to make the crystals anhydrous, then simply (but carefully) heating the crystalline solid in a clean glass beaker allows formation of the anhydrous salt. The color of the resulting product depends on the size of the crystals from which you start. With crystals of mm size, you obtain a chocolate brown solid. If you start from very fine crystals or powder you obtain a mustard-colored powder. The chocolate brown solid also can be ground to a mustard yellow/brown powder.  This must be done carefully so as to avoid decomposition into HCl. If you do it right however, there should be little to no HCl contamination.

Below, I will add some pictures that I will take of this experiment.  Sorry for the horrible photo quality, these were taken from my ipod.  I will get my better camera later and take some more close up pictures of the actual crystals.  As you can see, in the evaporating dish, there is a concentrated solution of copper (II) chloride.  The more concentrated it is, the darker green color it is. When it is relatively dilute, it is a more bluish color.  The crystals themselves are very needle like and small.  When you touch them, they feel spongy and even sort of wet, even though they aren't.  I'll post some more pictures soon.


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