Sulphur dioxide. Formula, production, chemical properties

Sulfur oxide (sulfur dioxide, sulfur dioxide, sulfur dioxide anhydride) is a colorless gas that has in normal conditions a sharp characteristic odor (similar to the smell of a lighted match). It liquefies under pressure at room temperature. Sulfur dioxide is soluble in water, and unstable sulfuric acid is formed. This substance also dissolves in sulfuric acid and ethanol. This is one of the main components that make up volcanic gases.

How to get sour gas

The production of SO2 - sulfur dioxide - in an industrial way consists in burning sulfur or burning sulphides (mainly pyrite is used).

4FeS2 (pyrite) + 11O2 = 2Fe2O3 (iron oxide) + 8SO2 (sulphurous gas).

Under laboratory conditions, sulfur dioxide can be obtained by the action of strong acids on hydrosulfites and sulfites. At the same time, the resulting sulfur dioxide immediately decomposes into water and sulfur dioxide. For example:

Na2SO3 (sodium sulphite) + H2SO4 (sulfuric acid) = Na2SO4 (sodium sulfate) + H2SO3 (sulfuric acid).
H2SO3 (sulfuric acid) = H2O (water) + SO2 (sulfur dioxide).

The third method of obtaining sulfurous anhydride consists in the action of concentrated sulfuric acid on heating to low-active metals. For example: Cu (copper) + 2H2SO4 (sulfuric acid) = CuSO4 (copper sulfate) + SO2 (sulfur dioxide) + 2H2O (water).

Chemical Properties of Sulfur Dioxide

The formula of sulfur dioxide is SO3. This substance refers to acidic oxides.

1. Sulfur dioxide dissolves in water, with the formation of sulfuric acid. Under normal conditions, this reaction is reversible.

SO2 (sulfur dioxide) + H2O (water) = H2SO3 (sulfuric acid).

2. With alkalis, sulfur dioxide forms sulphites. For example: 2NaOH (sodium hydroxide) + SO2 (sour gas) = Na2SO3 (sodium sulfite) + H2O (water).

3. The chemical activity of sulfur dioxide is quite high. The reducing properties of sulfurous anhydride are most pronounced. In such reactions, the degree of sulfur oxidation increases. For example: 1) SO2 (sulfur dioxide) + Br2 (bromine) + 2H2O (water) = H2SO4 (sulfuric acid) + 2HBr (hydrobromide); 2) 2SO2 (sulfur dioxide) + O2 (oxygen) = 2SO3 (sulfite); 3) 5SO2 (sulfur dioxide) + 2KMnO4 (potassium permanganate) + 2H2O (water) = 2H2SO4 (sulfuric acid) + 2MnSO4 (manganese sulfate) + K2SO4 (potassium sulphate).

The latter reaction is an example of a qualitative reaction to SO2 and SO3. There is a discoloration of the solution of violet color).

4. In the presence of strong reducing agents, sulfurous anhydride may exhibit oxidizing properties. For example, to recover sulfur from the exhaust gases in the metallurgical industry, the reduction of sulfur dioxide with carbon monoxide (CO) is used: SO2 (sulfur dioxide) + 2CO (carbon monoxide) = 2CO2 (carbon dioxide) + S (sulfur).

Also, the oxidizing properties of this substance are used for the production of phosphorus-rich xylitol: PH3 (phosphine) + SO2 (sulphurous gas) = H3PO2 (phosphoric acid) + S (sulfur).

Where sulfur dioxide is used

Basically, sulfur dioxide is used to produce sulfuric acid. Also it is used as a preservative (E-220) in the production of low-alcohol beverages (wine and other drinks of the middle price category). Due to the property of this gas, to kill various microorganisms, they fumigate storage facilities and vegetable stores. In addition, sulfur oxide is used for bleaching wool, silk, straw (those materials that can not be bleached with chlorine). In laboratories, sulfur dioxide is used as a solvent and in order to obtain various salts of sulfuric acid.

Physiological effects

Sulfur gas has strong toxic properties. Symptoms of poisoning - a cough, runny nose, hoarseness of voice, a kind of taste in the mouth, a strong perspiration in the throat. When sulfur dioxide is inhaled in high concentrations, it becomes difficult to swallow and choke, speech disorder, nausea and vomiting, possibly the development of acute pulmonary edema.

MPC of sulfur dioxide:
- indoors - 10 mg / m³;
- The average daily maximum-time in the ambient air is 0.05 mg / m³.

Sensitivity to sulfur dioxide in individuals, plants and animals is different. For example, among trees the oak and birch are the most stable, and the least - spruce and pine.