Hydrogen Chloride

In Chemistry, even though Chlorine and Hydrogen Chloride is given as different elements, we always tend to study them together. They both share a closer relationship. For example, most of the HCl is produced as a co-product of the reactions by involving chlorine. Therefore, basically, this makes it desirable to consider both the chemical substances together. As being said, let us look at the methods for the preparation of Chlorine and Hydrogen Chloride.

Hydrogen Chloride

Firstly, Hydrogen Chloride was prepared in 1648 by Glauber by the process of heating sodium chloride with the concentrated H2SO4. Whereas, in 1840, Davy explained that HCl is a compound mixed with hydrogen and chlorine. The hydrochloric acid common name is given as muriatic acid.

Production of Hydrogen Chloride

Most of the hydrogen chloride produced on an industrial scale can be used for hydrochloric acid production.

Direct Synthesis

Very pure hydrogen chloride can be produced by combining the chlorine and hydrogen. The chemical reaction for the same is given as follows:

Cl2 + H2 → 2 HCl

Since the reaction is exothermic, we can refer to the installation as either an HCl burner or an HCl oven. The resultant hydrogen chloride gas can be absorbed in deionized water by resulting in the chemically pure hydrochloric acid. Also, this reaction gives a very pure product, for example, for the food industry usage.

Organic Synthesis

Hydrogen chloride’s industrial production is often integrated by forming fluorinated and chlorinated organic compounds, For example, Freon, Teflon, and other CFCs and chloroacetic acid, PVC well, etc. The production of hydrochloric acid is often integrated with its captive on-site use. In the case of chemical reactions, hydrogen atoms present on the hydrocarbon can be replaced by the chlorine atoms, whereupon the hydrogen atom which is released recombines with the spare atom from the chlorine molecule by forming the hydrogen chloride. Fluorination is given as a subsequent reaction of chlorine-replacement by producing again hydrogen chloride, where the chemical reaction can be given as follows:

R−H + Cl₂ → R−Cl + HCl

R−Cl + HF → R−F + HCl

The resultant hydrogen chloride can be either absorbed in water or reused directly, resulting in hydrochloric acid of industrial or technical grade.

Properties of Hydrogen Chloride

• HCl has a pungent aroma, and it is an uncoloured gas.

• Hydrochloric acid is given as the aqueous solution of the hydrogen chloride.

• HCl is soluble in water.

• It liquefies at a temperature of 189K to produce a colourless liquid and freezes at a temperature of 159k to produce a white solid.

Uses of Hydrogen Chloride Gas

• HCl can be used in the preparation of aqua regia, chlorine, including other chlorides.

• It can also act as a reagent in laboratories.

• It can be used as a solvent to dissolve noble gases.

Chlorine

Chlorine holds an atomic number 35, and in the periodic table, this compound occupies group 17 and period 3. The chemistry behind chlorine plays a key role in meeting the everyday requirements. Scientists around the world are working on the advancements in modern medicines and renewable energies. In 1774, Scheele discovered the presence of this greenish-yellow gas by noticing the HCl action on MnO2. This particular gas was not given a name until Davy had rooted its elementary description and recommended the name according to the colour of the gas.

Preparation of Cl2

The chlorine gas can be prepared using any of the following processes:

• When the Manganese dioxide is heated with concentrated HCl. The reaction is given as follows:

                                             MnO2 + 4HCl → MnCl2 + Cl2+ 2H2O

• Concentrated HCl acid is replaced by a combination of common salt and concentrated H2SO4. The reaction is given as follows:

                                 4NaCl + MnO2 + H2SO4 → MnCl2 + 4NaHSO4 + 2H2O + Cl2

• HCl in action with pottasium permanganate results in the following reaction:

                                     2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2

Other Processes to Prepare Chlorine

Deacon’s Method: In this specific method, Cl2 is obtained by oxidizing the HCl gases with oxygen in the catalyst presence. CuCl2 also acts as a catalyst at 723k in this process.

Electrolytic Process: In this particular process, brine undergoes electrolysis. Brine is defined as a concentrated solution of sodium chloride. After the process of electrolysis, Cl2 is discharged at the anode.

Properties of Cl2

• Cl2 is given as a gas having a pungent odour and greenish-yellow colouration.

• The gas nature is poisonous.

• This gas boils at a temperature of 239.11K and melts at a temperature of 171.6K.

• Chlorine water can be produced when Cl2 is dissolved in water. The yellow colour of the water becomes dissipated when exposed to the sunlight because of HCl and hypochlorous acid formation. This particular hypochlorous acid, which is formed, is unstable, and hence it decomposes to form nascent oxygen, which is responsible for oxidizing and bleaching action of Cl2.

Cl2 + → H2O (sunlight) HCl + HOCl

          2HOCl + 2HCl → 2[O]

• Cl₂ is also highly electronegative in nature

• Cl₂ gas contains a great affinity towards hydrogen, and it reacts with hydrogen to produce HCl.