How does hydrochloric acid form?

Question

How does hydrochloric acid form?

Answer 1

What is commonly called hydrochloric acid with the chemicall formulla HCl is actually a solution of hydrogen chloride gas dissolved in water. On an industrial scale, the HCl gas is produced in the chlor-alkali industry. A salt NaCl,  solution is electrolyzed producing chlorine (Cl2), sodium hydroxide(NaOH), and hydrogen (H2). The pure chlorine gas can be re-combined with the H2 gas forming hydrogen chloride gas.

Cl2 + H2 → 2HCl

As the reaction is exothermic, the installation is called an HCl oven. The resulting hydrogen chloride gas is absorbed in deionized water, resulting in chemically pure hydrochloric acid. This reaction can give a very pure product, e.g. for use in the food industry.

Small amounts of HCl gas for laboratory use can be generated in a HCl generator by dehydrating hydrochloric acid in two ways:

Liberation from concentrated hydrochloric acid by the addition of sulfuric acid.

Liberation from concentrated hydrochloric acid by the addition of anhydrous calcium chloride.

Alternatively, HCl can be generated by the reaction of sulfuric acid with sodium chloride:

2NaCl + H2SO4  Na2SO4 + 2HCl↑

This latter method is probably the most common in teaching laboratories.

Answer 2

Hydrochloric acid is the aqueous solution of hydrogen chloride gas (HCl). It is a strong acid, and the major component of gastric acid.[1] It is also widely used in industry. Hydrochloric acid must be handled with appropriate safety precautions because it is a highly corrosive solution. Historically called Muriatic acid, it has been an important and frequently-used chemical from early history, and was discovered by the alchemist Jabir ibn Hayyan in the 8th century. It was used throughout the Middle Ages by alchemists in the quest for the philosopher's stone, and later by several European scientists including Glauber, Priestley, and Davy in order to help establish modern chemical knowledge.

From the Industrial Revolution, it became a very important industrial chemical for many applications, including the large-scale production of organic compounds, such as vinyl chloride for PVC plastic, and MDI/TDI for polyurethane, and smaller-scale applications, such as production of gelatin and other ingredients in food, and leather processing. About 20 million metric tonnes of HCl gas are produced annually.

Hydrochloric acid is prepared by dissolving hydrogen chloride in water. Hydrogen chloride can be generated in many ways, and thus several precursors to hydrochloric acid exist. The large-scale production of hydrochloric acid is almost always integrated with other industrial scale chemicals production.

Hydrochloric acid is produced in solutions up to 38% HCl (concentrated grade). Higher concentrations up to just over 40% are chemically possible, but the evaporation rate is then so high that storage and handling need extra precautions, such as pressure and low temperature. Bulk industrial-grade is therefore 30% to 34%, optimized for effective transport and limited product loss by HCl vapors. Solutions for household purposes in the US, mostly cleaning, are typically 10% to 12%, with strong recommendations to dilute before use. In the United Kingdom where it is sold as "Spirits of Salt" for domestic cleaning, the potency is the same as the US industrial grade.

Major producers worldwide include Dow Chemical at 2 million metric tonnes annually (2 Mt/year), calculated as HCl gas, and FMC, Georgia Gulf Corporation, Tosoh Corporation, Akzo Nobel, and Tessenderlo at 0.5 to 1.5 Mt/year each. Total world production, for comparison purposes expressed as HCl, is estimated at 20 Mt/year, with 3 Mt/year from direct synthesis, and the rest as secondary product from organic and similar syntheses. By far, most of all hydrochloric acid is consumed captively by the producer. The open world market size is estimated at 5 Mt/year.

Answer 3

Hydrochloric acid is an aqueous solution of hydrogen chloride gas.  To make hydrochloric acid, hydrogen chloride gas is bubbled into water until it is saturated.

I just did a little demo with my AP chem class, to remind them of this.  Often, when you open a bottle of HCl, you will get a puff of vapor (which is actually a collection of water droplets that the HCl(g) has caused to condense).  I held some wet litmus paper over the open bottle (in the fume hood) and it turned red.

Since the solution in the bottle is saturated, it is in equilibrium with HCl gas above the solution.  When the top is removed some HCl gas diffuses out of the bottle and dissolves in the water on the litmus paper, producing hydrochloric acid, and turning the litmus indicator red.

Answer 4

Hydrogen chloride (HCl) is a monoprotic acid, which means it can dissociate (i.e., ionize) only once to give up one H+ ion (a single proton). In aqueous hydrochloric acid, the H+ joins a water molecule to form a hydronium ion, H3O+:

        HCl + H2O → H3O+ + Cl−

The other ion formed is Cl−, the chloride ion. Hydrochloric acid can therefore be used to prepare salts called chlorides, such as sodium chloride. Hydrochloric acid is a strong acid, since it is fully dissociated in water. As hydrochloric acid has fully dissociated the reaction is not reversible