The Chemistry Behind Chlorine And Hydrogen Chloride

Introduction

In Chemistry, even though Hydrogen Chloride and Chlorine are different elements we tend to study them together. Besides, they share a close relationship, for example, most HCl is produced as a co-product of reactions involving chlorine. So this basically makes it desirable to consider the two chemical substances together. That being said, here we will look at the methods for the preparation of Hydrogen Chloride and Chlorine.

Table of Contents

• Hydrogen Chloride
• Preparation of Hydrogen Chloride
• Properties of Hydrogen Chloride
• Uses of Hydrogen Chloride
• Chlorine
• Preparation of Cl2

Hydrogen Chloride

Hydrogen Chloride was first prepared in the year 1648 by Glauber by heating sodium chloride with concentrated

Preparation of Hydrogen Chloride

Muriatic acid is prepared by warming NaCl crystals with concentrated H2SO4 (Sulphuric acid).

Usually, most of the hydrogen chloride/hydrochloric acid that is formed is a co-product of some other chemical reactions. HCl is also formed by the chlorination of hydrocarbons.

Properties of Hydrogen Chloride

• HCl is an uncoloured gas and has a pungent aroma.
• Hydrochloric acid is the aqueous solution of hydrogen chloride.
• HCl is soluble in water.
• It liquefies at 189K to form a colourless liquid and freezes at 159k to form a white solid.

Uses of Hydrogen Chloride

• HCl is used in the preparation of chlorine, aqua regia, and other chlorides.
• It is used as a solvent to dissolve noble gases.
• It acts as a reagent in laboratories.

Chlorine

Chlorine has an atomic number 17 and occupies group 17 and period 3 in the periodic table. The chemistry behind chlorine plays a vital role in meeting the daily requirements. At the same time scientists around the world work on the advancements in renewable energies and modern medicines. In the year 1774, Scheele discovered the presence of this greenish-yellow gas by observing the action of HCl on MnO2. This gas wasn’t given a name until Davy rooted its elementary description and recommended the name based on the colour of the gas.

Preparation of Cl2

This gas can be prepared in any of the following processes:

• When Manganese dioxide is heated with concentrated HCl.

MnO₂+4HCl→MnCl₂+Cl₂+2H₂O

• Conc. HCl acid can be replaced by a combination of conc. H₂SO₄ and common salt.

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

• HCl in action with potassium permanganate gives

2KMnO₄+16HCl→2KCl+2MnCl₂+8H₂O+5Cl₂

Other processes to prepare Chlorine.

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

Deacon’s method: In this method Cl₂ is obtained by oxidising HCl gases with oxygen in the presence of a catalyst. CuCl₂ acts as a catalyst in this process at 723 K.

Properties of Cl2

• Cl₂ is a gas with greenish-yellow colouration and pungent odour.
• The nature of the gas is poisonous.
• The gas boils at 239.11K and melts at 171.6K.
• Chlorine water is formed when Cl₂ is dissolved in water. The yellow colour of the water gets dissipated when exposed to the sunlight due to the formation of hypochlorous acid and HCl. This hypochlorous acid formed is unstable, hence it decomposes to give nascent oxygen which is responsible for the bleaching and oxidising action of Cl₂.

Cl₂ + H₂O → HCl + HOCl

HOCl → HCl + [O]

• Cl₂ is highly electronegative in nature
• Cl₂ has great affinity towards hydrogen. It reacts with hydrogen to form HCl.

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