Sulfuric acid on physical properties – heavy oily liquid. It has no smell and color, is hygroscopic, is well dissolved in water. Less than 70% usually call solution with the maintenance of H2SO4 the diluted sulfuric acid, more than 70% – concentrated.
Acid and main properties of sulfuric acid
All properties of strong acids are characteristic of the diluted sulfuric acid. It dissociates in solution on the equation: H2SO4↔2H (+) + SO4(2-), interacts with the main oxides, the bases and salts: MgO+H2SO4=MgSO4+H2O, H2SO4+2NaOH=Na2SO4+2H2O, H2SO4+BaCl2=BaSO4 ↓+2HCl. Reaction with ions of Ba (2+) barium – high-quality reaction to sulfate ion at which the insoluble white deposit of BaSO4 drops out.
Oxidation-reduction properties of sulfuric acid
Sulfuric acid shows properties of oxidizer: diluted – at the expense of hydrogen H ions (+), concentrated – for the account SO4(2-) sulfate ions. Sulfate ions are stronger oxidizers, than hydrogen ions.
The metals standing in an electrochemical number of tension are more left than hydrogen, are dissolved in the diluted sulfuric acid. During such reactions, hydrogen is emitted and sulfates of metals are formed: Zn+H2SO4 (razb.) =ZnSO4+H2 ↑. Metals which stand in an electrochemical number of tension after hydrogen with the diluted sulfuric acid do not react. The concentrated sulfuric acid – strong oxidizer, especially when heating. In it many metals, nonmetals and a number of organic matter are oxidized. The metals standing in an electrochemical number of tension after hydrogen (copper, silver, mercury) are oxidized to sulfates. A product of restoration of sulfuric acid is sulphurous SO2 gas. More active metals, such as zinc, aluminum and magnesium, in reaction from the concentrated H2SO4 also give sulfates, but acid can be restored not only to sulphurous gas, but also to hydrogen sulfide or free sulfur (depending on concentration): Zn+2H2SO4 (konts.) =ZnSO4+SO2 ↑+2H2O, 3Zn+4H2SO4 (konts.) =3ZnSO4+S ↓+4H2O, 4Zn+5H2SO4 (konts.) =4ZnSO4+H2S +4N2O.Nekotorye metals, such as iron and aluminum, are in the cold passivated by the concentrated sulfuric acid. For this reason it is often transported in iron tanks: Fe+H2SO4 (konts.) ≠ (in the cold). At oxidation of nonmetals, for example, of sulfur and carbon, the concentrated sulfuric acid is restored to SO2: S+2H2SO4 (konts.) = 3SO2 ↑+2H2O, C+2H2SO4=2SO2 ↑+CO2 ↑+2H2O.
As receive sulfuric acid
In the industry sulfuric acid is received in several stages. At first roasting of FeS2 pyrite receive SO2, then in the presence of the V2O5 catalyst it is oxidized in SO3 oxide, and after SO3 dissolve in sulfuric acid. The oleum is so formed. To receive acid of the required concentration, the received oleum is carefully flowed in water (not on the contrary!).