Hydrochloric Acid

Formula: HCl

World production: 20 million metric tons

Hydrochloric acid is used in numerous different processes. One of particular importance is in the digestive process of the human body. Hydrochloric acid is stored in your stomach and helps break down food and nutrients. Industrially, it is used in a process known as "pickling" in which metals (steel or iron) are immersed in the acid to remove impurities such as rust. It can also be used in the production of organic compounds such as vinyl chloride or BPA (used in plastics). Many food products, such as aspartame, fructose, and vegetable protein, also rely on hydrochloric acid in their production. In low concentrations, it can be used as a household cleaner.

How it's made:
There are two common methods.

Direct synthesis occurs when brine of NaCl and Water is electrolyzed, producing Chlorine gas (Cl2), Sodium Hydroxide (NaOH), and Hydrogen gas (H2). The Chlorine and Hydrogen can then be combined in the presence of UV light to produce HCl. H2(g) + Cl2(g)→ 2 HCl(g). The resulting gas is absorbed by deionized water, becoming a HCl solution, or hydrochloric acid.

In Organic synthesis, a hydrogen atom in a hydrocarbon is replaced by a chlorine atom from chlorine gas (Cl2(g)). The released hydrogen atom from the hydrocarbon combines with the other chlorine atom from the gas to form HCl(g). This can then be absorbed in water to produce hydrochloric acid.

Nitric Acid

Formula: HNO3

World production: 60 million metric tons

The main use for nitric acid is in fertilizer. When combined with ammonia, the acid is neutralized and the resulting compound is ammonium nitrate, a fertilizer. This use accounts for ~80% of nitric acid produced. Other uses include the production of explosives and rocket fuel. It can also be used as a pickling agent for stainless steel and a cleaning agent in certain food production facilities.

How it's made:
First, nitric oxide (NO) is produced by oxidizing anhydrous ammonia. The nitric oxide combined with oxygen to produce nitrogen dioxide (NO2). Nitric acid is then produced by combining Nitrogen Dioxide with water, to yield nitric acid and nitric oxide. 3 NO2 + H2O → 2 HNO3 + NO.

Sulfuric Acid

Formula: H2SO4

World production: 180 million metric tons (produced in greater quantity than any other chemical in the world)

The main use (~60%) for sulfuric acid is in production of fertilizer. It is used to dissolve phosphate rock to produce phosphoric acid, which in turn is used to manufacture phosphate fertilizers. It is also used as an industrial cleaning agent, to clean iron and steel products, and as a catalyst in a number of other production processes (including the production of hydrochloric acid). In the household, it is used in drain cleaners and as the electrolyte in lead-acid car batteries.

How it's made:
There are two main methods:

The Contact process starts with the combination of sulfur and oxygen through combustion. The sulfur dioxide (SO2) that is produced is oxidized to form sulfur trioxide (SO3). This is combined with existing sulfuric acid to form oleum (H2S2O7), which when mixed with water will form H2SO4. As you can see in the reaction, twice as much sulfuric acid will be produced. H2S2O7 + H2O → 2 H2SO4.

The wet sulfuric acid process is similar to the first. Sulfur dioxide is produced and oxidized to form Sulfur trioxide. This is then hydrated (combined with water) to form sulfuric acid as a gas, and then condensed to form aqueous sulfuric acid. SO3 + H2O → H2SO4.