Sulfuric acid is an inorganic dibasic unstable acid of medium strength. An unstable compound, known only in aqueous solutions at a concentration of not more than six percent. When trying to isolate pure sulfuric acid, it decomposes into sulfur oxide (SO2) and water (H2O). For example, when sulfuric acid (H2SO4) is concentrated in the form of sodium sulfite (Na2SO3), sulfur oxide (SO2) is released instead of sulfur dioxide. This is what the reaction looks like:
Na2SO3 (sodium sulfite) + H2SO4 (sulfuric acid) = Na2SO4 (sodium sulfate) + SO2 (sulfur dioxide) + H2O (water)
Sulfuric Acid Solution
During its storage it is necessary to exclude air access. Otherwise, sulfuric acid, slowly absorbing oxygen (O2), will turn into sulfuric acid.
2H2SO3 (sulfuric acid) + O2 (oxygen) = 2H2SO4 (sulfuric acid)
Sulfuric acid solutions have a rather specific odor (reminiscent of the odor remaining after a match is lit), the presence of which can be explained by the presence of sulfur oxide (SO2), not chemically bound by water.
Chemical Properties of Sulfuric Acid
1. Sulfuric acid (formula H2SO3) can be used as a reducing agent or an oxidizing agent.
H2SO3 is a good reducing agent. With its help, hydrogen halides can be obtained from free halogens. For instance:
H2SO3 (sulfuric acid) + Cl2 (chlorine, gas) + H2O (water) = H2SO4 (sulfuric acid) + 2HCl (hydrochloric acid)
But when interacting with strong reducing agents, this acid will act as an oxidizing agent. An example is the reaction of sulfurous acid with hydrogen sulfide:
H2SO3 (sulfuric acid) + 2H2S (hydrogen sulfide) = 3S (sulfur) + 3H2O (water)
2. The chemical compound under consideration forms two types of salts - sulfites (medium) and hydrosulfites (acidic). These salts are reducing agents, as is (H2SO3) sulphurous acid. When they are oxidized, sulfuric acid salts are formed. Annealing sulfites of active metals produces sulfates and sulfides. This is a self-oxidation-self-healing reaction. For instance:
4Na2SO3 (sodium sulfite) = Na2S (sodium sulfide) + 3Na2SO4 (sodium sulfate)
Sodium and potassium sulfites (Na2SO3 and K2SO3) are used for dyeing fabrics in the textile industry, for bleaching metals, as well as in photography. Calcium hydrosulfite (Ca (HSO3) 2), which exists only in solution, is used to process wood material into special sulfite cellulose. Then they make paper out of it.
The use of sulphurous acid
Sulfuric acid is used:
- for bleaching wool, silk, wood pulp, paper and other similar substances that cannot withstand bleaching with the help of stronger oxidizing agents (for example, chlorine);
- as a preservative and antiseptic, for example, to prevent the fermentation of grain when receiving starch or to prevent the fermentation process in barrels of wine;
- to preserve products, for example, when preserving vegetables and fruits;
- in the processing of wood chips into sulphite pulp, from which paper is then obtained. In this case, a solution of calcium hydrosulfite (Ca (HSO3) 2) is used, which dissolves lignin - a special substance that binds cellulose fibers.
Sulfuric acid: preparation
This acid can be obtained by dissolving sulfur dioxide (SO2) in water (H2O). You will need sulfuric acid in concentrated form (H2SO4), copper (Cu) and a test tube. Algorithm of actions:
1. Carefully pour concentrated sulfuric acid into the tube and then place a piece of copper there. Heat up. The following reaction occurs:
Cu (copper) + 2H2SO4 (sulfuric acid) = CuSO4 (sulfur sulfate) + SO2 (sulfur dioxide) + H2O (water)
2. The flow of sulfur dioxide must be directed into a test tube with water. When it is dissolved, a chemical reaction partially occurs with water, as a result of which sulfurous acid is formed:
SO2 (sulfur dioxide) + H2O (water) = H2SO3
So, by passing sulfur dioxide gas through water, sulfur dioxide can be obtained. It is worth considering that this gas has an irritating effect on the membranes of the respiratory tract, can cause inflammation, as well as loss of appetite. With prolonged inhalation, loss of consciousness is possible. Handle this gas with extreme caution and care.