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How sulphuric acid can be used in the preparation of hydrochloric acid? Name the reagents used and write chemical equations.

Last updated date: 13th Jun 2024
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Hint: The large-scale production of hydrochloric acid is almost always associated with the large-scale production of other chemical compounds, like the chlor alkali process which produces hydroxide, hydrogen, and chlorine, the latter of which can be combined to produce hydrochloric acid.
The reagents which are used in the production of hydrochloric acid are namely sodium chloride and sulfuric acid, which substitutes the chloride present in sodium chloride and donates a proton for that chloride ion.

Complete step by step answer:
Manufacture of Hydrogen Chloride or hydrochloric acid can be done in the industries by the use of common salt along with sulphuric acid.
We produce hydrochloric acid in the laboratory by treating sodium chloride along with concentrated sulphuric acid. Next we expose the mixture to high temperature as in, heat this mixture up to $420K$


As we can see that the sodium chloride which was present as a reactant, reacts with the sulphuric acid at high temperature and then formation of products take place. The products formed are hydrochloric acid and sodium hydrogen sulphate. The Sodium bisulphate which we got as a by-product is insoluble in the solvent. So, we further mix this product with more sodium chloride which we took as one of the reactants. After we get this mixture, it has to be warmed further up to a higher temperature which is usually around $823K$. This will give dissolvable sodium sulphate along with hydrochloric acid in gaseous form. This can be chemically represented by the following reaction:


Now in this step we treat sodium chloride along with that sodium bisulphate which we got as a side product in the previous reaction. We get sodium sulphate along with hydrochloric acid.
We dry this hydrochloric acid which we got from this reaction, by treating it with concentrated sulphuric acid. Hydrochloric acid is not dried over brisk lime or phosphorus pentoxide. This is because it reacts with both of these compounds. This is the whole process of production of Hydrochloric acid by using sulphuric acid as oxidising agent, which itself gets reduced.

Note: 1.Hydrochloric acid is a strong inorganic acid that is used in many industrial processes such as refining metal. The application often determines the required product quality
2.Hydrochloric acid is a vapid gas. It has a very sharp and pungent odour.
3.It melts into a colourless fluid at $189K$. Hydrochloric acid can form a white solid at $159K$upon freezing.