Sulfur trioxide is usually a colorless liquid. It can also exist as ice, fibrous crystals, or gas. When sulfur trioxide is exposed to air, white smoke begins to be released. It is an integral element of such a reactive substance as concentrated sulfuric acid. It is a clear, colorless, oily and highly corrosive liquid. It is used in the manufacture of fertilizers, explosives, other acids, the oil industry, and lead-acid batteries in automobiles.
Concentrated sulfuric acid: properties
Sulphuric acid It dissolves well in water, is corrosive to metals and fabrics, and chars wood and most other organic substances on contact. Long-term exposure to low concentrations or short-term exposure to high concentrations may result in adverse health effects from inhalation.
Concentrated sulfuric acid is used to make fertilizers and other chemicals, in oil refining, in iron and steel production, and for many other purposes. Because it has a high enough boiling point, it can be used to release more volatile acids from their salts. Concentrated sulfuric acid has a strong hygroscopic property. It is sometimes used as a drying agent for dehydration (removal of water chemical method) of many compounds, such as carbohydrates.
Sulfuric acid reactions
Concentrated sulfuric acid reacts in an unusual way to sugar, leaving behind a brittle spongy black mass of carbon. A similar reaction is observed when exposed to skin, cellulose and other plant and animal fibers. When concentrated acid is mixed with water, a large amount of heat is released, enough to boil instantly. For dilution, it should be added slowly to cold water with constant stirring to limit heat buildup. Sulfuric acid reacts with liquid, forming hydrates with pronounced properties.
physical characteristics
A colorless and odorless liquid in a dilute solution has a sour taste. Sulfuric acid is extremely aggressive when exposed to the skin and all tissues of the body, with direct contact causes severe burns. In its pure form, H 2 SO4 is not a conductor of electricity, but the situation changes in the opposite direction with the addition of water.
Some properties is that the molecular weight is 98.08. The boiling point is 327 degrees Celsius, the melting point is -2 degrees Celsius. Sulfuric acid is a strong mineral acid and one of the main products of the chemical industry due to its wide commercial use. It is formed naturally from the oxidation of sulfide materials such as iron sulfide.
The chemical properties of sulfuric acid (H 2 SO4) are manifested in various chemical reactions:
- When interacting with alkalis, two series of salts are formed, including sulfates.
- Reacts with carbonates and hydrocarbonates to form salts and carbon dioxide(CO 2).
- It affects metals differently, depending on the temperature and degree of dilution. Cold and dilute yields hydrogen, hot and concentrated yields SO 2 emissions.
- When boiling, a solution of H 2 SO4 (concentrated sulfuric acid) decomposes into sulfur trioxide (SO 3) and water (H 2 O). The chemical properties also include the role of a strong oxidizing agent.
fire hazard
Sulfuric acid is highly reactive to ignite fine combustible materials on contact. When heated, highly toxic gases begin to be released. It is explosive and incompatible with a huge number of substances. At elevated temperatures and pressures, rather aggressive chemical changes and deformation. May react violently with water and other liquids, causing splashing.
health hazard
Sulfuric acid corrodes all tissues of the body. Inhalation of vapors can cause serious lung damage. Damage to the mucous membrane of the eyes can lead to complete loss of vision. Skin contact may cause severe necrosis. Even a few drops can be fatal if the acid gains access to the windpipe. Chronic exposure can cause tracheobronchitis, stomatitis, conjunctivitis, gastritis. Gastric perforations and peritonitis may occur, accompanied by circulatory collapse. Sulfuric acid is a highly caustic substance that must be handled with extreme care. Signs and symptoms upon exposure can be severe and include drooling, intense thirst, difficulty swallowing, pain, shock, and burns. The vomit is usually the color of ground coffee. Acute inhalation exposure may result in sneezing, hoarseness, choking, laryngitis, dyspnea, irritation respiratory tract and chest pain. Bleeding from the nose and gums, pulmonary edema, chronic bronchitis, and pneumonia may also occur. Exposure to the skin can result in severe painful burns and dermatitis.
First aid
- Move victims to fresh air. Emergency personnel should avoid exposure to sulfuric acid while doing so.
- Assess vital signs, including pulse and respiratory rate. If a pulse is not detected, perform resuscitation, depending on the additional injuries received. If breathing is present and difficult, provide respiratory support.
- Remove soiled clothing as soon as possible.
- In case of contact with eyes, rinse with warm water for at least 15 minutes; for skin, wash with soap and water.
- When inhaling toxic fumes, rinse your mouth with plenty of water, drink and self-induce vomiting is prohibited.
- Deliver the injured to a medical facility.
Pure 100% sulfuric acid (monohydrate) is a colorless oily liquid that solidifies into a crystalline mass at +10 °C. Reactive sulfuric acid usually has a density of 1.84 g/cm 3 and contains about 95% H 2 SO 4 . It hardens only below -20 °C.
The melting point of the monohydrate is 10.37 °C with a heat of fusion of 10.5 kJ/mol. Under normal conditions, it is a very viscous liquid with a very high dielectric constant (e = 100 at 25 °C). Insignificant own electrolytic dissociation of the monohydrate proceeds in parallel in two directions: [Н 3 SO 4 + ]·[НSO 4 - ] = 2 10 -4 and [Н 3 О + ]·[НS 2 О 7 - ] = 4 10 - 5 . Its molecular-ionic composition can be approximately characterized by the following data (in %):
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When even small amounts of water are added, dissociation becomes predominant according to the scheme:
H 2 O + H 2 SO 4<==>H 3 O + + HSO 4 -
Chemical properties.
H 2 SO 4 is a strong dibasic acid.
H2SO4<-->H + + HSO 4 -<-->2H + + SO 4 2-
The first stage (for medium concentrations) leads to 100% dissociation:
K 2 \u003d ( ) / \u003d 1.2 10 -2
1) Interaction with metals:
a) dilute sulfuric acid dissolves only metals that are in the series of voltages to the left of hydrogen:
Zn 0 + H 2 +1 SO 4 (razb) --> Zn +2 SO 4 + H 2 O
b) concentrated H 2 +6 SO 4 - a strong oxidizing agent; when interacting with metals (except Au, Pt), it can be reduced to S +4 O 2, S 0 or H 2 S -2 (Fe, Al, Cr also do not react without heating - they are passivated):
2Ag 0 + 2H 2 +6 SO 4 --> Ag 2 +1 SO 4 + S +4 O 2 + 2H 2 O
8Na 0 + 5H 2 +6 SO 4 --> 4Na 2 +1 SO 4 + H 2 S -2 + 4H 2 O
2) concentrated H 2 S +6 O 4 reacts when heated with some non-metals due to its strong oxidizing properties, turning into sulfur compounds of a lower oxidation state, (for example, S + 4 O 2):
С 0 + 2H 2 S +6 O 4 (conc) --> C +4 O 2 + 2S +4 O 2 + 2H 2 O
S 0 + 2H 2 S +6 O 4 (conc) --> 3S +4 O 2 + 2H 2 O
2P 0 + 5H 2 S +6 O 4 (conc) --> 5S +4 O 2 + 2H 3 P +5 O 4 + 2H 2 O
3) with basic oxides:
CuO + H2SO4 --> CuSO4 + H2O
CuO + 2H + --> Cu 2+ + H 2 O
4) with hydroxides:
H 2 SO 4 + 2NaOH --> Na 2 SO 4 + 2H 2 O
H + + OH - --> H 2 O
H 2 SO 4 + Cu(OH) 2 --> CuSO 4 + 2H 2 O
2H + + Cu(OH) 2 --> Cu 2+ + 2H 2 O
5) exchange reactions with salts:
BaCl 2 + H 2 SO 4 --> BaSO 4 + 2HCl
Ba 2+ + SO 4 2- --> BaSO 4
The formation of a white precipitate of BaSO 4 (insoluble in acids) is used to identify sulfuric acid and soluble sulfates.
The monohydrate (pure, 100% sulfuric acid) is an ionizing solvent having an acidic character. Sulfates of many metals are well dissolved in it (turning into bisulfates), while salts of other acids are dissolved, as a rule, only if their solvolysis is possible (with conversion to bisulfates). Nitric acid behaves in monohydrate as weak base
HNO 3 + 2 H 2 SO 4<==>H 3 O + + NO 2 + + 2 HSO 4 -
perchloric - as a very weak acid
H 2 SO 4 + HClO 4 = H 3 SO 4 + + ClO 4 -
Fluorosulfonic and chlorosulfonic acids are somewhat stronger (HSO 3 F> HSO 3 Cl> HClO 4). The monohydrate dissolves well many organic substances containing atoms with unshared electron pairs (capable of attaching a proton). Some of these can then be isolated back unchanged by simply diluting the solution with water. The monohydrate has a high cryoscopic constant (6.12°) and is sometimes used as a medium for determining molecular weights.
Concentrated H 2 SO 4 is a fairly strong oxidizing agent, especially when heated (it is usually reduced to SO 2). For example, it oxidizes HI and partially HBr (but not HCl) to free halogens. It also oxidizes many metals - Cu, Hg, etc. (whereas gold and platinum are stable with respect to H 2 SO 4). So the interaction with copper goes according to the equation:
Cu + 2 H 2 SO 4 \u003d CuSO 4 + SO 2 + H 2 O
Acting as an oxidizing agent, sulfuric acid is usually reduced to SO 2 . However, it can be reduced to S and even H 2 S with the strongest reducing agents. Concentrated sulfuric acid reacts with hydrogen sulfide according to the equation:
H 2 SO 4 + H 2 S \u003d 2H 2 O + SO 2 + S
It should be noted that it is also partially restored hydrogen gas and therefore cannot be used to dry it.
Rice. 13. Electrical conductivity of sulfuric acid solutions.
The dissolution of concentrated sulfuric acid in water is accompanied by a significant release of heat (and some decrease in the total volume of the system). Monohydrate almost does not conduct electricity. In contrast, aqueous solutions of sulfuric acid are good conductors. As seen in fig. 13, approximately 30% acid has the maximum electrical conductivity. The minimum of the curve corresponds to a hydrate with the composition H 2 SO 4 ·H 2 O.
The release of heat upon dissolution of the monohydrate in water is (depending on the final concentration of the solution) up to 84 kJ/mol H 2 SO 4 . On the contrary, by mixing 66% sulfuric acid, pre-cooled to 0 ° C, with snow (1: 1 by weight), a decrease in temperature can be achieved, down to -37 ° C.
The change in the density of aqueous solutions of H 2 SO 4 with its concentration (wt.%) is given below:
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As can be seen from these data, the determination of the density of the concentration of sulfuric acid above 90 wt. % becomes quite inaccurate.
Water vapor pressure over H 2 SO 4 solutions of different concentrations at different temperatures is shown in fig. 15. Sulfuric acid can act as a drying agent only as long as the water vapor pressure over its solution is less than its partial pressure in the gas being dried.
Rice. 15. Water vapor pressure.
Rice. 16. Boiling points over solutions of H 2 SO 4 . H 2 SO 4 solutions.
When a dilute sulfuric acid solution is boiled, water is distilled off from it, and the boiling point rises up to 337 ° C, when 98.3% H 2 SO 4 begins to distill (Fig. 16). On the contrary, excess sulfuric anhydride volatilizes from more concentrated solutions. The steam of sulfuric acid boiling at 337 ° C is partially dissociated into H 2 O and SO 3, which recombine upon cooling. The high boiling point of sulfuric acid allows it to be used to isolate volatile acids from their salts (for example, HCl from NaCl) when heated.
Receipt.
The monohydrate can be obtained by crystallization of concentrated sulfuric acid at -10°C.
Sulfuric acid production.
1st stage. Pyrite kiln.
4FeS 2 + 11O 2 --> 2Fe 2 O 3 + 8SO 2 + Q
The process is heterogeneous:
1) grinding iron pyrite (pyrite)
2) "fluidized bed" method
3) 800°С; removal of excess heat
4) increase in the concentration of oxygen in the air
2nd stage.After cleaning, drying and heat exchange, sulfur dioxide enters the contact apparatus, where it is oxidized to sulfuric anhydride (450 ° C - 500 ° C; catalyst V 2 O 5):
2SO2 + O2<-->2SO3
3rd stage. Absorption tower:
nSO 3 + H 2 SO 4 (conc) --> (H 2 SO 4 nSO 3) (oleum)
Water cannot be used due to the formation of fog. Apply ceramic nozzles and the principle of counterflow.
Application.
Remember! Sulfuric acid must be poured into water in small portions, and not vice versa. Otherwise, violent chemical reaction which could result in severe burns.
Sulfuric acid is one of the main products of the chemical industry. It goes to the production of mineral fertilizers (superphosphate, ammonium sulfate), various acids and salts, medicines and detergents, dyes, artificial fibers, explosives. It is used in metallurgy (decomposition of ores, for example, uranium), for the purification of petroleum products, as a desiccant, etc.
Practically important is the fact that very strong (above 75%) sulfuric acid does not act on iron. This allows you to store and transport it in steel tanks. On the contrary, dilute H 2 SO 4 easily dissolves iron with the release of hydrogen. Oxidizing properties are not typical for it at all.
Strong sulfuric acid absorbs moisture vigorously and is therefore often used to dry gases. From many organic substances containing hydrogen and oxygen, it takes away water, which is often used in technology. With this (as well as oxidizing properties strong H 2 SO 4) is associated with its destructive effect on plant and animal tissues. Sulfuric acid that accidentally gets on the skin or dress during work should be immediately washed off with plenty of water, then moisten the affected area with a dilute ammonia solution and rinse again with water.
Molecules of pure sulfuric acid.
Fig.1. Diagram of hydrogen bonds in an H 2 SO 4 crystal.
The molecules that form the monohydrate crystal, (HO) 2 SO 2 are connected to each other by fairly strong (25 kJ/mol) hydrogen bonds, as shown schematically in Fig. 1. The (HO) 2 SO 2 molecule itself has the structure of a distorted tetrahedron with a sulfur atom near the center and is characterized by the following parameters: (d (S-OH) \u003d 154 pm, PHO-S-OH \u003d 104 °, d (S \u003d O) \u003d 143 pm, ROSO \u003d 119 °.In the HOSO 3 - ion, d (S-OH) \u003d 161 and d (SO) \u003d 145 pm, and when going to the SO 4 ion, the 2-tetrahedron acquires the correct shape and the parameters are aligned.
Sulfuric acid hydrates.
For sulfuric acid, several crystalline hydrates are known, the composition of which is shown in Fig. 14. Of these, the poorest in water is the oxonium salt: H 3 O + HSO 4 -. Since the system under consideration is very prone to supercooling, the freezing temperatures actually observed in it are much lower than the melting points.
Rice. 14. Melting points in the H 2 O·H 2 SO 4 system.
Acid with metal is specific for these classes of compounds. In its course, the hydrogen proton is restored and, in conjunction with the acid anion, is replaced by a metal cation. This is an example of a salt-forming reaction, although there are several types of interactions that do not follow this principle. They proceed as redox and are not accompanied by hydrogen evolution.
Principles of reactions of acids with metals
All reactions with metal lead to the formation of salts. The only exception is, perhaps, the reaction of a noble metal with aqua regia, a mixture of hydrochloric acid, and any other interaction of acids with metals leads to the formation of a salt. If the acid is neither concentrated sulfuric nor nitric, then molecular hydrogen is split off as a product.
But when concentrated sulfuric acid reacts, the interaction with metals proceeds according to the principle of a redox process. Therefore, two types of interactions of typical metals and strong inorganic acids were experimentally distinguished:
- interaction of metals with dilute acids;
- interaction with concentrated acid.
Reactions of the first type proceed with any acid. The only exception is concentrated and nitric acid of any concentration. They react according to the second type and lead to the formation of salts and products of sulfur and nitrogen reduction.
Typical interactions of acids with metals
Metals located to the left of hydrogen in the standard electrochemical series react with other acids of various concentrations, with the exception of nitric acid, to form a salt and release molecular hydrogen. Metals located to the right of hydrogen in the electronegativity series cannot react with the above acids and interact only with nitric acid, regardless of its concentration, with concentrated sulfuric acid and with aqua regia. This is a typical interaction of acids with metals.
Reactions of metals with concentrated sulfuric acid
Reactions with dilute nitric acid
Dilute nitric acid reacts with metals to the left and right of hydrogen. During the reaction with active metals, ammonia is formed, which immediately dissolves and interacts with the nitrate anion, forming another salt. with metals average activity the acid reacts with the release of molecular nitrogen. With inactive, the reaction proceeds with the release of dinitric oxide. Most often, several sulfur reduction products are formed in one reaction. Examples of reactions are suggested in the graphical appendix below.
Reactions with concentrated nitric acid
AT this case Nitrogen is also an oxidizing agent. All reactions end with the formation of salt and isolation. Schemes of the course of redox reactions are proposed in the graphical application. In this case, the reaction with inactive elements deserves special attention. Such interaction of acids with metals is nonspecific.
Reactivity of metals
Metals react with acids quite readily, although there are several inert substances. These are elements that have a high standard electrochemical potential. There are a number of metals that are built on the basis of this indicator. It's called the electronegativity series. If the metal is in it to the left of hydrogen, then it is able to react with dilute acid.
There is only one exception: iron and aluminum, due to the formation of trivalent oxides on their surface, cannot react with acid without heating. If the mixture is heated, then initially the oxide film of the metal enters into the reaction, and then it dissolves in the acid itself. Metals located to the right of hydrogen in the electrochemical series of activity cannot react with inorganic acid, including with diluted chamois. There are two exceptions to the rule: these metals dissolve in concentrated and dilute nitric acid and aqua regia. Only rhodium, ruthenium, iridium and osmium cannot be dissolved in the latter.
Any acid is a complex substance, the molecule of which contains one or more hydrogen atoms and an acid residue.
The formula of sulfuric acid is H2SO4. Therefore, the composition of the sulfuric acid molecule includes two hydrogen atoms and the acid residue SO4.
Sulfuric acid is formed when sulfur oxide reacts with water
SO3+H2O -> H2SO4
Pure 100% sulfuric acid (monohydrate) is a heavy liquid, viscous like oil, colorless and odorless, with a sour "copper" taste. Already at a temperature of +10 ° C, it solidifies and turns into a crystalline mass.
Concentrated sulfuric acid contains approximately 95% H2SO4. And it freezes at temperatures below -20 ° C.
Interaction with water
Sulfuric acid is highly soluble in water, mixing with it in any ratio. This releases a large amount of heat.
Sulfuric acid is able to absorb water vapor from the air. This property is used in industry for drying gases. Gases are dried by passing them through special containers with sulfuric acid. Of course, this method can only be used for those gases that do not react with it.
It is known that when sulfuric acid comes into contact with many organic substances, especially carbohydrates, these substances are charred. The fact is that carbohydrates, like water, contain both hydrogen and oxygen. Sulfuric acid robs them of these elements. What remains is coal.
AT aqueous solution H2SO4 indicators litmus and methyl orange turn red, which indicates that this solution has a sour taste.
Interaction with metals
Like any other acid, sulfuric acid is capable of replacing hydrogen atoms with metal atoms in its molecule. It interacts with almost all metals.
dilute sulfuric acid reacts with metals like a normal acid. As a result of the reaction, a salt with an acidic residue SO4 and hydrogen are formed.
Zn + H2SO4 = ZnSO4 + H2
BUT concentrated sulfuric acid is a very strong oxidizing agent. It oxidizes all metals, regardless of their position in the voltage series. And when reacting with metals, it itself is reduced to SO2. Hydrogen is not released.
Сu + 2 H2SO4 (conc) = CuSO4 + SO2 + 2H2O
Zn + 2 H2SO4 (conc) = ZnSO4 + SO2 + 2H2O
But gold, iron, aluminum, platinum group metals do not oxidize in sulfuric acid. Therefore, sulfuric acid is transported in steel tanks.
Sulfuric acid salts, which are obtained as a result of such reactions, are called sulfates. They are colorless and crystallize easily. Some of them are highly soluble in water. Only CaSO4 and PbSO4 are sparingly soluble. BaSO4 is almost insoluble in water.
Interaction with bases
The reaction of an acid with a base is called a neutralization reaction. As a result of the neutralization reaction of sulfuric acid, a salt containing the acid residue SO4 and water H2O is formed.
Examples of sulfuric acid neutralization reactions:
H2SO4 + 2 NaOH = Na2SO4 + 2 H2O
H2SO4 + CaOH = CaSO4 + 2 H2O
Sulfuric acid enters into a neutralization reaction with both soluble and insoluble bases.
Since there are two hydrogen atoms in the sulfuric acid molecule, and two bases are required to neutralize it, it belongs to dibasic acids.
Interaction with basic oxides
From the school chemistry course, we know what oxides are called complex substances, which includes two chemical element, one of which is oxygen in the -2 oxidation state. Basic oxides are called oxides of 1, 2 and some 3 valence metals. Examples of basic oxides: Li2O, Na2O, CuO, Ag2O, MgO, CaO, FeO, NiO.
With basic oxides, sulfuric acid enters into a neutralization reaction. As a result of such a reaction, as in the reaction with bases, salt and water are formed. The salt contains the acid residue SO4.
CuO + H2SO4 = CuSO4 + H2O
Salt interaction
Sulfuric acid reacts with salts of weaker or volatile acids, displacing these acids from them. As a result of this reaction, a salt with an acidic residue SO4 and an acid
H2SO4+BaCl2=BaSO4+2HCl
The use of sulfuric acid and its compounds
Barium porridge BaSO4 is able to delay x-rays. Filling it with the hollow organs of the human body, radiologists examine them.
In medicine and construction, natural gypsum CaSO4 * 2H2O, calcium sulfate hydrate is widely used. Glauber's salt Na2SO4 * 10H2O is used in medicine and veterinary medicine, in the chemical industry - for the production of soda and glass. Copper sulfate CuSO4 * 5H2O is known to gardeners and agronomists who use it to control pests and plant diseases.
Sulfuric acid is widely used in various industries: chemical, metalworking, petroleum, textile, leather and others.
With dilute acids, which exhibit oxidizing properties due tohydrogen ions(diluted sulphuric, phosphoric, sulphurous, all anoxic and organic acids and etc.)
metals react:
located in a series of voltages to hydrogen(these metals are able to displace hydrogen from the acid);
forming with these acids soluble salts(protective salt does not form on the surface of these metals)
film).
As a result of the reaction, soluble salts and stand out hydrogen:
2A1 + 6HCI \u003d 2A1C1 3 + ZN 2
M g + H 2 SO 4 \u003d M gS O 4 + H 2
razb.
FROM u + H 2 SO 4 →
X
(because C u stands after H 2)
razb.
Pb + H 2 SO 4 →
X
(because Pb SO 4 insoluble in water)
razb.
Some acids are oxidizing agents due to the element that forms an acid residue. These include concentrated sulfuric acid, as well as nitric acid of any concentration. Such acids are called oxidizing acids.
The oxidizing properties of acidic residues are much stronger than those of hydrogen H, therefore nitric and concentrated sulfuric acids interact with almost all metals located in the voltage series both before and after hydrogen, other than gold and platinum. Since the oxidizing agents in these cases are nones of acid residues (due to sulfur and nitrogen atoms in the highest oxidation states), and not nons of hydrogen H, then in the interaction of nitric, and concentrated sulfuric acids With metals do not release hydrogen. The metal under the action of these acids is oxidized to characteristic (stable) oxidation state and forms a salt, and the product of acid reduction depends on the activity of the metal and the degree of dilution of the acid
The interaction of sulfuric acid with metals
Dilute and concentrated sulfuric acids behave differently. Dilute sulfuric acid behaves like ordinary acid. Active metals in the voltage series to the left of hydrogen
Li, K, Ca, Na, Mg, Al, Mn, Zn, Fe, Co, Ni, Sn, Pb, H2, Cu, Hg, Ag, Au
displace hydrogen from dilute sulfuric acid. We see hydrogen bubbles when dilute sulfuric acid is added to a test tube with zinc.
H 2 SO 4 + Zn \u003d Zn SO 4 + H 2
Copper is in the series of voltages after hydrogen - therefore, dilute sulfuric acid does not act on copper. And in concentrated sulfuric acid, zinc and copper behave in this way ...
Zinc, like active metal, maybe form with concentrated sulfuric acid, sulfur dioxide, elemental sulfur, and even hydrogen sulfide.
2H 2 SO 4 + Zn \u003d SO 2 + ZnSO 4 + 2H 2 O
Copper is a less active metal. When interacting with concentrated sulfuric acid, it reduces it to sulfur dioxide.
2H 2 SO 4 conc. + Cu \u003d SO 2 + CuSO 4 + 2H 2 O
In test tubes with concentrated Sulfuric acid releases sulfur dioxide.
It should be borne in mind that the diagrams indicate products whose content is maximum among the possible products of acid reduction.
Based on the above schemes, we will compose the equations for specific reactions - the interaction of copper and magnesium with concentrated sulfuric acid:
0 +6
+2 +4
FROM u + 2H 2 SO 4 \u003d C uSO 4 + SO 2 + 2H 2 O
conc.
0 +6 +2 -2
4M g + 5H 2 SO 4 \u003d 4M gSO 4 + H 2 S + 4H 2 O
conc.
Some metals ( Fe. AI, Cr) do not interact with concentrated sulfuric and nitric acid at normal temperature, as it happens passivation metal. This phenomenon is associated with the formation of a thin but very dense oxide film on the metal surface, which protects the metal. For this reason, nitric and concentrated sulfuric acids are transported in iron containers.
If the metal exhibits variable oxidation states, then with acids that are oxidizing agents due to H + ions, it forms salts in which its oxidation state is lower than stable, and with oxidizing acids, salts in which its oxidation state is more stable:
0 +2
F e + H 2 SO 4 \u003d F e SO 4 + H 2
0 razb. + 3
F e + H 2 SO 4 \u003d F e 2 (SO 4) 3 + 3 SO 2 + 6H 2 O
conc
I.I. Novoshinsky
N.S.Novoshinskaya
