How is chlorine gas produced

chlorine

discovery

The gas chlorine was discovered by Carl Wilhelm Scheele in 1774 when he used brown stone with conc. Hydrochloric acid drizzled. Basically, this experiment is still carried out in chemistry classes today when chlorine is used in the gas generator made of potassium permanganate and conc. Produces hydrochloric acid.

Interestingly, Scheele did not realize that chlorine was an element. He thought it was an oxygen compound of hydrochloric acid. The idea is not entirely absurd: if you mix hydrochloric acid with the extremely oxygen-rich KMnO4 lets react and if manganese chloride MnCl2 arises, i.e. a manganese compound that has "lost" its oxygen.

It was only in 1808 that Humpry David recognized that chlorine is an element. He had tried several times to split the oxygen from the "oxygen compound" chlorine, which of course did not succeed. DAVY also gave the element the name "chlorine", which comes from the Greek chloros and means something like "light green".

Occurrence

The very reactive halogen hardly occurs as a free element. Elemental chlorine is only found in volcanic gases or in the ozone layer, but only in small quantities.

In contrast, it is found in bound form in many salts, especially in the chlorides. The most important chloride is probably rock salt (table salt, sodium chloride). In addition to NaCl, the rock salt stores mainly contain KCl and MgCl2. Chlorine contributes 0.19% to the structure of the earth's crust, which means that it is in 19th position in terms of the abundance of elements. Sea water also contains sodium chloride, potassium chloride and other chlorides, about 3% in total.

presentation

In the laboratory, chlorine is produced by the reaction of potassium permanganate with conc. Hydrochloric acid obtained, alternatively you can also use manganese (IV) oxide with conc. Let hydrochloric acid react. The reaction of potassium permanganate takes place according to the following equation:

This is a redox reaction in which the permanganate ion is reduced and the chloride ion of the hydrochloric acid is oxidized.

Manufacturing

In industry, chlorine is produced by chlor-alkali electrolysis. Either an NaCl solution or an NaCl melt is electrolyzed. In 2006 almost 60 million tons of chlorine were produced on earth.

In the past, chlorine was also synthesized using the Deacon process; today this is only practiced to a limited extent. In the Deacon process, hydrogen chloride HCl is oxidized by atmospheric oxygen in the presence of a catalyst:

Copper chloride is often used as a catalyst.

properties
Physical Properties

Chlorine is a yellow-green gas with a pungent odor like "swimming pool". Prolonged inhalation can cause severe burns and ultimately death. When chlorine gas is cooled to -34.6ºC, it condenses to a yellow liquid. Cooling further to -101 ° C produces a yellow-green solid. Chlorine is very soluble in water; 2.3 liters of chlorine gas dissolve in 1 liter of water at room temperature. The density of chlorine is 3.2 g / l (at 0 ºC), which means that chlorine gas is about 2.5 times as heavy as air. Chlorine can be easily liquefied under pressure and can then be transported in steel bottles.

chemical properties

Chlorine is extremely reactive, it reacts with most elements and with many compounds, including organic compounds.

Reaction with metals

With metals, chlorine forms salts, namely the chlorides, in mostly exothermic reactions. The more noble the metal, the less exothermic the reaction is. The reaction with alkali metals and alkaline earth metals already takes place at room temperature, more noble metals such as copper or silver have to be heated to a greater or lesser extent so that they react with chlorine. Moist (water-containing) chlorine reacts with metals much more violently than dry chlorine.

The corresponding metal chlorides are formed during the reaction. Metals of the subgroups such as iron can also form several different chlorides, from iron there is, for example, FeCl2 and the FeCl3.

Reaction with non-metals

With hydrogen, chlorine forms the strong acid hydrogen chloride HCl, the aqueous solution of which is known as hydrochloric acid. This reaction is also extremely exothermic (chlorine-oxyhydrogen gas reaction). Chlorine hardly or not at all reacts with other non-metals.

Reaction with organic compounds

Chlorine reacts with alkanes and alkyl compounds in a radical substitution reaction to form haloalkanes; methane and chlorine can be used to produce, for example, mono-, di-, tri- or tetrachloromethane. Electrophilic addition occurs with alkenes and alkynes, and electrophilic substitution is possible with aromatics if a suitable catalyst is present.

use
Use earlier

In the past, chlorine was mainly used as a bleaching agent. Today you don't do that anymore; Even in industry, other processes are used for bleaching (textiles, paper, etc.).

The use of chlorine as a poison gas in World War I is notorious. Because of its high density, the gas mainly accumulated in the trenches and killed many enemy soldiers. Some experts assume that chlorine was also used as a poison gas by government troops in Syria in May 2014 (barrel bombs).

Use today

Chlorine is an important raw material (basic chemical) in the chemical industry. Many inorganic and organic compounds are made using chlorine.

Important inorganic chlorine compounds are hypochlorite, chlorate, chlorine dioxide, disulphur dichloride and some other important organic chlorine compounds are carbon tetrachloride, chloroform and monomers of chlorinated plastics, for example vinyl chloride, from which the plastic PVC is then produced. Incidentally, vinyl chloride is the most important chlorine product of all. In 1997, 33% of the world's chlorine production was used for the production of vinyl chloride.

In swimming pools or in the preparation of drinking water, chlorine is used as a water-soluble disinfectant.