Copper(II) chloride

Copper(II) chloride, also known as cupric chloride, is an inorganic compound with the chemical formula CuCl₂. It exists in two main forms: a yellowish-brown anhydrous form and a blue-green dihydrate form, which contains two water molecules of hydration[/w/7]. The anhydrous form slowly absorbs moisture from the air to become the dihydrate.

This compound is made in factories for use as a co-catalyst in the Wacker process[/w/9], an important industrial method.

Both forms of copper(II) chloride can also be found naturally as rare minerals. The anhydrous form is called tolbachite, and the dihydrate form is called eriochalcite.

Structure

Copper(II) chloride has a special shape. In its dry form, it looks like a structure found in cadmium iodide, with copper placed in shapes called octahedrons. Many copper compounds have slightly changed octahedron shapes because of something called the Jahn-Teller effect. This effect happens when one electron stays in a special area that pushes away two chloride pieces.

When copper(II) chloride has water added, it still keeps this changed octahedron shape. The copper is surrounded by two water pieces and four chloride pieces, which connect to other copper pieces in a special way.

Copper(II) chloride can attract magnetic fields. It was used in the very first experiments to study this magnetic property by Yevgeny Zavoisky in 1944.

Anhydrous

Dihydrate

Properties and reactions

When you dissolve copper(II) chloride in water, it creates different copper shapes that change color depending on how much of it you use, the temperature, and if there are other chloride bits around. You might see blue colors from one shape and yellow or red colors from another.

If you add a base to copper(II) chloride in water, it forms a blue solid called copper(II) hydroxide. This can also create a special mix called dicopper chloride trihydroxide, which is used to keep plants healthy.

Copper(II) chloride can slowly break down when left in air without extra acid. It can also break apart when heated, producing copper(I) chloride and chlorine gas. It mixes with certain metals and other substances to form new shapes and compounds.

Preparation

Copper(II) chloride is made by mixing copper with chlorine gas at high heat. This creates copper(II) chloride in liquid form. Another way to make it is by adding chlorine gas to a mix of hydrochloric acid and copper, then evaporating the solution to get the form that includes water.

Some copper compounds can also react with hydrochloric acid to form copper(II) chloride, which can then be heated to remove the water. The solution can be cleaned by letting crystals form when cooled in a special ice bath. There are other less common ways to create copper(II) chloride using electricity, but these are not usually chosen because they can release harmful gases.

Uses

Copper(II) chloride is used in industry as a helper in a process called the Wacker process. This process changes a gas called ethene into a liquid called ethanal using water and air. Copper(II) chloride helps keep another helper, palladium(II) chloride, working properly during this change.

Copper(II) chloride also has special uses in making other chemicals. It can help add chlorine to certain compounds and can change some materials in specific ways. It is also used to help make chlorine gas in some industrial processes. In addition, it is used to give a blue or green color in fireworks, and it can be found in special cards that show changes in humidity. It also has uses in the textile industry, cleaning water, and preserving wood.

Natural occurrence

Copper(II) chloride can be found in nature as two rare minerals: tolbachite, which has no water, and eriochalcite, which has two water molecules. These minerals are usually found near openings in the earth where hot gases come out and in some places where copper is mined. There are also more common minerals made of copper, oxygen, and chlorine, like atacamite, which form in dry areas where copper ores are found.

Safety and biological impact

Copper(II) chloride can be harmful if not handled properly. It is important to keep concentrations of copper ions below 1.3 parts per million in drinking water, as recommended by the US Environmental Protection Agency. If someone absorbs copper chloride, they might feel a headache, have stomach trouble, experience a drop in blood pressure, and get a fever. Eating very large amounts can cause serious health problems.

Studies have shown that copper(II) chloride can change the normal behavior of cells in plants, such as onions, and may harm tiny living things in water and soil. It has been found to affect certain bacteria that help clean water, showing that even small amounts can be damaging to the environment.