What Is the Connection between Sodium Chloride and Sulfuric Acid?

Sodium chloride and sulfuric acid are two compounds that are often used in laboratories and manufacturing organizations for a variety of purposes. These two may also be used for reactions with one another, in order to yield two other products, hydrochloric acid and sodium hydrogen sulfate, which can also be useful. For small-scale production, this reaction is one of the preferred means of creating hydrochloric acid.

Usually, sodium chloride (NaCl) and sulfuric acid (H₂SO₄) are combined with the salt in its solid form, and the acid diluted in water. Generally, the reaction of sodium chloride and sulfuric acid takes place in a well-ventilated area, with a source of heat to speed up the reaction. While the production of hydrochloric acid (HCl) and sodium hydrogen sulfate (NaHSO₄) can take place at room temperature under certain conditions, heating allows this reaction to proceed much more quickly and thoroughly. Additionally, while concentrated sulfuric acid can also react properly, it is usually more dangerous to work with, and a solution of water and acid can still produce sufficient HCl for most limited-use lab purposes.

One common laboratory device that is used in the mixing of sodium chloride and sulfuric acid is known as an HCl generator. This device allows for the high temperatures needed for the reaction to take place quickly, as well as ventilation and glassware to capture the HCl as it is formed, because it is created in a gaseous form. The NaHSO₄ is produced as a molten liquid, which can be captured in the glass vessel in which the reaction takes place, and cooled down into a solid for later use. When the two reactants, sodium chloride and sulfuric acid, are combined, the reaction can be written out as NaCl + H₂SO₄ ---> HCl + NaHSO₄.

In this reaction, one proton from the acid leaves, forming a temporary reactant, H₃O+. The proton then joins the chlorine ion, which easily dissociates from the sodium ion in the solution due to the high polarity, or electrical charge, of both of these ions. Heat that is added during this reaction of sodium chloride and sulfuric acid allows the reaction to proceed to completion.

Both sulfuric acid and hydrochloric acid are extremely corrosive substances, which are capable of reacting with water quickly. Unless the products from this reaction are contained, the gaseous hydrochloric acid could potentially come into contact with the person performing it, causing injury or death. Consequently, this reaction is usually only undertaken by individuals with a strong background in chemistry, under laboratory conditions, with safety equipment.