About the definition of sulfuric acid,

About the definition of sulfuric acid,

Sulfuric acid, chemical formula: H2SO4, colorless and odorless oily liquid, strong acid with high boiling point and difficult to volatilize, easily soluble in water, and can be miscible with water in any ratio. Strong corrosivity, strong oxidation, molecular relative mass: 98.08. When concentrated sulfuric acid dissolves, a large amount of heat is released. Therefore, when concentrated sulfuric acid is diluted, it should "put acid into water, pour slowly along the wall, and stir continuously.", So sulfuric acid containing SO3 is called fuming sulfuric acid
100% sulfuric acid, melting point 10 ℃, boiling point 290 ℃
1. Dehydration
(1) as far as sulfuric acid is concerned, dehydration is the property of concentrated sulfuric acid, not that of dilute sulfuric acid
(2) dehydration is the chemical property of concentrated sulfuric acid. The dehydration process of substance by concentrated sulfuric acid is the process of chemical change. During the reaction, concentrated sulfuric acid is dehydrated by water
The ratio of the number of hydrogen and oxygen atoms in the dehydrated product (2 ∶ 1) captures the hydrogen and oxygen atoms in the dehydrated product
(3) the substances that can be dehydrated by concentrated sulfuric acid are generally organic substances containing hydrogen and oxygen elements, among which the organic substances in sucrose, sawdust, paper and cotton are dehydrated to form black carbon (carbonization)
(1) reaction with metal
① At room temperature, concentrated sulfuric acid can passivate iron, aluminum and other metals
② When heated, concentrated sulfuric acid can react with all metals except gold and platinum to form high valence metal sulfate, which is generally reduced to SO2
Cu + 2h2so4 (concentrated) = = (heated) = = CuSO4 + SO2 ↑ + 2H2O
2Fe + 6h2so4 (concentrated) = = = = Fe2 (SO4) 3 + 3so2 ↑ + 6H2O
In the above reaction, sulfuric acid shows strong oxidation and acidity
(2) reaction with nonmetal
Hot concentrated sulfuric acid can oxidize carbon, sulfur, phosphorus and other non-metallic elements to their high valence oxides or oxygen-containing acids, and itself is reduced to SO2
Concentrated sulfuric acid only shows oxidation in the reaction
C + 2h2so4 (concentrated) = (heated) = = CO2 ↑ + 2so2 ↑ + 2H2O
S + 2h2so4 (concentrated) = = = 3so2 ↑ + 2H2O
2p + 5h2so4 (concentrated) = = = = 2h3po4 + 5so2 ↑ + 2H2O
(3) reaction with other reducing substances
Concentrated sulfuric acid has strong oxidizability, so it can't be used to produce reducing gases such as H 2S, HBr and hi in laboratory
H2S + H2SO4 (concentrated) = = = s ↓ + SO2 ↑ + 2H2O
2hbr + H2SO4 (concentrated) = = = = Br2 ↑ + SO2 ↑ + 2H2O
2hi + H2SO4 (concentrated) = = = = I2 ↑ + SO2 ↑ + 2H2O
3. Water absorption
As far as sulfuric acid is concerned, water absorption has many uses. For example, many gases can be dried with concentrated sulfuric acid. It is a good desiccant
This is very different from the dehydration: generally, there is no water before the dehydration reaction, but h and O elements form water in the form of 2:1, which comes out from the organic matter
The water absorption is water before the reaction, but sulfuric acid acts as a desiccant in the process
CuSO 4 · 5h 2O → (H 2SO 4) → CuSO 4 + 5h 2O, this reaction reflects the water absorption of sulfuric acid, not the dehydration, because there is water before the reaction
In addition, in the process of producing ethylene in the laboratory, the water absorption of concentrated sulfuric acid is reflected, which promotes the reaction to proceed in the direction of positive reaction. In some reactions with sulfuric acid as catalyst, especially concentrated sulfuric acid, the water absorption of sulfuric acid is generally reflected
If a bottle of concentrated sulfuric acid is placed in the air, its mass will increase, its density will decrease, its concentration will decrease, and its volume will increase, because concentrated sulfuric acid has water absorption
As far as sulfuric acid is concerned, water absorption is the property of concentrated sulfuric acid, not the property of dilute sulfuric acid
(2) the water absorption of concentrated sulfuric acid refers to the strong combination of concentrated sulfuric acid molecules and water molecules to form a series of stable hydrates and release a lot of heat: H2SO4 + nH2O = = H2SO4 · nH2O. Therefore, the water absorption process of concentrated sulfuric acid is a process of physical change, and the water absorption is the physical property of concentrated sulfuric acid
(3) concentrated sulfuric acid can absorb not only free water (such as water in air), but also water in some crystalline hydrates (such as CuSO4 · 5H2O, Na2CO3 · 10h2o)
4. Non volatile (high boiling point)
Preparation of hydrogen chloride, nitric acid, etc. (principle: preparation of volatile acid from non volatile acid) for example, preparation of hydrogen chloride gas by reaction of solid sodium chloride with concentrated sulfuric acid
NaCl (solid) + H2SO4 (concentrated) = = = NaHSO4 + HCl ↑ (normal temperature)
2nacl (solid) + H2SO4 (concentrated) = = = Na2SO4 + 2HCl ↑ (heated)
Na2SO3+H2SO4====Na2SO4+H2O+SO2↑
For another example, hydrogen chloride gas can be produced by using concentrated hydrochloric acid and concentrated sulfuric acid
Acidity: chemical fertilizer, such as nitrogen fertilizer, phosphorus fertilizer, etc
2NH3+H2SO4====(NH4)2SO4
Ca3(PO3)2+2H2SO4====2CaSO4+Ca(H2PO4)2
Stability: concentrated sulfuric acid reacts with sulfite
Na2SO3+H2SO4====Na2SO4+H2O+SO2↑