Chemical properties of salts. Examples of salts: chemical properties, preparation
Salt. Receipt and Chemical properties.
Let's look at the most important ways to obtain salts.
1. Neutralization reaction. Solutions of acid and base are mixed in the required molar ratio. After evaporating the water, a crystalline salt is obtained. For example:
2 . Reaction of acids with basic oxides . In fact, this is a variant of the neutralization reaction. For example:
3 . Reaction of bases with acid oxides . This is also a variant of the neutralization reaction:
4 . Reaction of basic and acidic oxides with each other :
5 . Reaction of acids with salts . This method is suitable, for example, if an insoluble salt is formed and precipitates:
6 . Reaction of bases with salts . Only alkalis (soluble bases) are suitable for such reactions. These reactions produce another base and another salt. It is important that the new base is not alkali and cannot react with the resulting salt. For example:
7. Reaction of two different salts. The reaction can be carried out only if at least one of the resulting salts is insoluble and precipitates:
The precipitated salt is filtered off, and the remaining solution is evaporated to obtain another salt. If both salts formed are highly soluble in water, then no reaction occurs: in the solution there are only ions that do not interact with each other:
NaCl + KBr = Na + + Cl + K + + Br
If we evaporate such a solution, we get mixture salts NaCl, KBr, NaBr and KCl, but pure salts cannot be obtained in such reactions.
8 . Reaction of metals with acids. Salts are also formed in redox reactions. For example, metals located to the left of hydrogen in the metal activity series (Table 4-3) displace hydrogen from acids and themselves combine with them, forming salts:
9 . Reaction of metals with nonmetals . This reaction looks like combustion. The metal “burns” in the current of the non-metal, forming tiny salt crystals that look like white “smoke”:
10 . Reaction of metals with salts. More active metals located in the activity series to the left, are able to displace less active ones (located to the right) metals from their salts:
Let's consider Chemical properties salts
Not a single process in the world is possible without the intervention of chemical compounds, which, reacting with each other, create the basis for favorable conditions. All elements and substances in chemistry are classified according to the structure and functions they perform. The basic ones are acids and bases. When they interact, soluble and insoluble salts are formed.
Examples of acids, salts
An acid is a complex substance that contains one or more hydrogen atoms and an acid residue. A distinctive property of such compounds is the ability to replace hydrogen with a metal or some positive ion, resulting in the formation of the corresponding salt. Almost all acids, with the exception of some (H 2 SiO 3 - silicic acid), are soluble in water, and strong ones, such as HCl (hydrochloric), HNO 3 (nitric), H 2 SO 4 (sulfuric), completely disintegrate into ions. And weak ones (for example, HNO 2 - nitrogenous, H 2 SO 3 - sulfurous) - partially. Their pH value (pH), which determines the activity of hydrogen ions in solution, is less than 7.
Salt is a complex substance, most often consisting of a metal cation and an acid residue anion. It is usually produced by the reaction of acids and bases. As a result of this interaction, water is still released. The salt cations can be, for example, NH 4 + cations. They, like acids, can dissolve in water with varying degrees of solubility.
Examples of salts in chemistry: CaCO 3 - calcium carbonate, NaCl - sodium chloride, NH 4 Cl - ammonium chloride, K 2 SO 4 - potassium sulfate and others.
Classification of salts
Depending on the amount of replacement of hydrogen cations, the following categories of salts are distinguished:
- Medium - salts in which hydrogen cations are completely replaced by metal cations or other ions. Such examples of salts in chemistry include the most ordinary substances which are most common are KCl, K 3 PO 4.
- Acidic - substances in which hydrogen cations are not completely replaced by other ions. Examples are sodium bicarbonate (NaHCO 3) and potassium hydrogen orthophosphate (K 2 HPO 4).
- Basic - salts in which the acid residues are not completely replaced by a hydroxo group when there is an excess of base or a lack of acid. These substances include MgOHCl.
- Complex salts: Na, K2.
Depending on the amount of cations and anions present in the salt, they are distinguished:
- Simple - salts containing one type of cation and anion. Examples of salts: NaCl, K 2 CO 3, Mg(NO3) 2.
- Double salts are salts that consist of a pair of types of positively charged ions. These include aluminum-potassium sulfate.
- Mixed - salts in which two types of anions are present. Examples of salts: Ca(OCl)Cl.
Obtaining salts
These substances are obtained mainly by reacting an alkali with an acid, resulting in the formation of water: LiOH + HCl = LiCl + H 2 O.
When acidic and basic oxides interact, salts are also formed: CaO + SO 3 = CaSO 4.
They are also obtained by the reaction of an acid and a metal that comes before hydrogen in the electrochemical voltage series. As a rule, this is accompanied by the release of gas: H 2 SO 4 + Li = Li 2 SO 4 + H 2.
When bases (acids) interact with acidic (basic) oxides, the corresponding salts are formed: 2KOH + SO 2 = K 2 SO 3 + H 2 O; 2HCl + CaO = CaCl 2 + H 2 O.
Basic salt reactions
When a salt and an acid interact, another salt and a new acid are obtained (the condition for such a reaction is that as a result a precipitate should form or a gas should be released): HCl + AgNO 3 = HNO 3 + AgCl.
When two different soluble salts react, the following is obtained: CaCl 2 + Na 2 CO 3 = CaCO 3 + 2NaCl.
Some salts that are poorly soluble in water have the ability to decompose into the corresponding reaction products when heated: CaCO 3 = CaO + CO 2.
Some salts can undergo hydrolysis: reversibly (if it is a salt of a strong base and a weak acid (CaCO 3) or a strong acid and a weak base (CuCl 2)) and irreversibly (a salt of a weak acid and a weak base (Ag 2 S)). Salts of strong bases and strong acids (KCl) do not hydrolyze.
They can also dissociate into ions: partially or completely, depending on the composition.
A large number of reactions leading to the formation of salts are known. We present the most important of them.
1. Interaction of acids with bases (neutralization reaction):
NaOH + HNO 3 = NANO 3 + N 2 ABOUT
Al(OH) 3 + 3HC1 =AlCl 3 + 3H 2 ABOUT
2. Interaction of metals with acids:
Fe + 2HCl = FeCl 2 + N 2
Zn+ N 2 SABOUT 4 div. = ZnSO 4 + N 2
3. Interaction of acids with basic and amphoteric oxides:
WITHuO+ N 2 SO 4 = CuSO 4 + N 2 ABOUT
ZnO + 2 HCl = ZnWITHl 2 + N 2 ABOUT
4. Interaction of acids with salts:
FeCl 2 + H 2 S = FeS + 2 HCl
AgNO 3 + HCl = AgCl +HNO 3
Ba(NO 3 ) 2 +H 2 SO 4 = BaSO 4 + 2HNO 3
5. Interaction of solutions of two different salts:
BaCl 2 +Na 2 SO 4 = VaSO 4 +2NаСl
Pb(NO 3 ) 2 + 2NaCl =RbWITH1 2 + 2NaNO 3
6. Interaction of bases with acid oxides (alkalis with amphoteric oxides):
Ca(OH) 2 + CO 2 = CaCO 3 + N 2 ABOUT,
2 Nand he (TV) + ZnO Na 2 ZnO 2 + N 2 ABOUT
7. Interaction of basic oxides with acidic ones:
CaO + SiO 2
CaSiO 3
Na 2 O+SO 3 = Na 2 SO 4
8. Interaction of metals with non-metals:
2K + S1 2 = 2KS1
Fe +S
FeS
9. Interaction of metals with salts.
Cu + Hg(NO 3 ) 2 = Hg + Cu(NO 3 ) 2
Pb(NO 3 ) 2 +Zn=Rb + Zn(NO 3 ) 2
10. Interaction of alkali solutions with salt solutions
CuCl 2 + 2NaOH = Cu(OH) 2 ↓+ 2NaCl
NaHCO 3 + NaOH = Na 2 CO 3 +H 2 O
Use of salts.
A number of salts are compounds necessary in significant quantities to ensure the vital functions of animal and plant organisms (sodium, potassium, calcium salts, as well as salts containing the elements nitrogen and phosphorus). Below, using examples of individual salts, the areas of application of representatives of this class of inorganic compounds, including in the oil industry, are shown.
NаС1- sodium chloride (table salt, table salt). The breadth of use of this salt is evidenced by the fact that the world production of this substance is more than 200 million tons.
This salt is widely used in the food industry and serves as a raw material for the production of chlorine, hydrochloric acid, sodium hydroxide, and soda ash. (Na 2 CO 3 ). Sodium chloride finds a variety of uses in the oil industry, for example, as an additive to drilling fluids to increase density, prevent the formation of cavities when drilling wells, as a regulator of the setting time of cement grouting compositions, to lower the freezing point (antifreeze) of drilling and cement fluids.
KS1- potassium chloride. Included in drilling fluids that help maintain the stability of well walls in clayey rocks. Potassium chloride is used in significant quantities in agriculture as a macrofertilizer.
Na 2 CO 3 - sodium carbonate (soda). Included in mixtures for glass production and detergents. Reagent for increasing the alkalinity of the environment, improving the quality of clays for clay drilling fluids. Used to remove the hardness of water when preparing it for use (for example, in boilers), widely used for cleaning natural gas from hydrogen sulfide and for the production of reagents for drilling and cementing fluids.
Al 2 (SO 4 ) 3 - aluminum sulfate. A component of drilling fluids, a coagulant for purifying water from fine suspended particles, a component of viscoelastic mixtures for isolating absorption zones in oil and gas wells.
NA 2 IN 4 ABOUT 7 - sodium tetraborate (borax). It is an effective reagent - a retarder for cement mortars, an inhibitor of thermal-oxidative destruction of protective reagents based on cellulose ethers.
BASABOUT 4 - barium sulfate (barite, heavy spar). Used as a weighting agent ( 4.5 g/cm 3) for drilling and cement slurries.
Fe 2 SO 4 - iron (I) sulfate (iron sulfate). It is used for the preparation of ferrochrome lignosulfonate - a reagent-stabilizer for drilling fluids, a component of highly effective emulsion hydrocarbon-based drilling fluids.
FeS1 3 - ferric chloride (III). In combination with alkali, it is used to purify water from hydrogen sulfide when drilling wells with water, for injection into hydrogen sulfide-containing formations in order to reduce their permeability, as an additive to cements in order to increase their resistance to the action of hydrogen sulfide, to purify water from suspended particles.
CaCO 3 - calcium carbonate in the form of chalk, limestone. It is a raw material for the production of quicklime CaO and slaked lime Ca(OH) 2. Used in metallurgy as a flux. It is used when drilling oil and gas wells as a weighting agent and filler for drilling fluids. Calcium carbonate in the form of marble with a certain particle size is used as a proppant during hydraulic fracturing of productive formations in order to enhance oil recovery.
CaSO 4 - calcium sulfate. In the form of alabaster (2СаSO 4 · Н 2 О) it is widely used in construction and is part of quick-hardening cementitious mixtures for isolating absorption zones. When added to drilling fluids in the form of anhydrite (CaSO 4) or gypsum (CaSO 4 · 2H 2 O), it imparts stability to the drilled clayey rocks.
CaCl 2 - calcium chloride. Used for preparing drilling and cementing solutions for drilling out unstable rocks, greatly reduces the freezing point of solutions (antifreeze). It is used to create high-density solutions that do not contain a solid phase, effective for opening productive formations.
NA 2 SiABOUT 3 - sodium silicate (soluble glass). Used to consolidate unstable soils and to prepare quick-setting mixtures to isolate absorption zones. It is used as a metal corrosion inhibitor, a component of some drilling cement and buffer solutions.
AgNO 3 - silver nitrate. Used for chemical analysis, including formation waters and drilling fluid filtrates for the content of chlorine ions.
Na 2 SO 3 - sodium sulfite. Used to chemically remove oxygen (deaeration) from water to combat corrosion during injection. Wastewater. To inhibit the thermal-oxidative destruction of protective reagents.
Na 2 Cr 2 ABOUT 7 - sodium bichromate. It is used in the oil industry as a high-temperature viscosity reducer for drilling fluids, an aluminum corrosion inhibitor, and for the preparation of a number of reagents.
The bases can interact:
- with non-metals -
6KOH + 3S → K2SO 3 + 2K 2 S + 3H 2 O;
- with acid oxides -
2NaOH + CO 2 → Na 2 CO 3 + H 2 O;
- with salts (precipitation, release of gas) -
2KOH + FeCl 2 → Fe(OH) 2 + 2KCl.
There are also other ways to get it:
- interaction of two salts -
CuCl 2 + Na 2 S → 2NaCl + CuS↓;
- reaction of metals and non-metals -
- combination of acidic and basic oxides -
SO 3 + Na 2 O → Na 2 SO 4;
- interaction of salts with metals -
Fe + CuSO 4 → FeSO 4 + Cu.
Chemical properties
Soluble salts are electrolytes and are subject to dissociation reactions. When interacting with water, they disintegrate, i.e. dissociate into positively and negatively charged ions - cations and anions, respectively. Cations are metal ions, anions are acidic residues. Examples of ionic equations:
- NaCl → Na + + Cl − ;
- Al 2 (SO 4) 3 → 2Al 3 + + 3SO 4 2− ;
- CaClBr → Ca2 + + Cl - + Br - .
In addition to metal cations, salts may contain ammonium (NH4 +) and phosphonium (PH4 +) cations.
Other reactions are described in the table of chemical properties of salts.
Rice. 3. Isolation of sediment upon interaction with bases.
Some salts, depending on the type, decompose when heated into a metal oxide and an acid residue or into simple substances. For example, CaCO 3 → CaO + CO 2, 2AgCl → Ag + Cl 2.
What have we learned?
From the 8th grade chemistry lesson we learned about the features and types of salts. Complex inorganic compounds consist of metals and acidic residues. May include hydrogen (acid salts), two metals, or two acid residues. These are solid crystalline substances that are formed as a result of reactions of acids or alkalis with metals. React with bases, acids, metals, and other salts.
There are 10 main methods for obtaining salts, * based on the chemical properties of the most important classes of inorganic compounds.
The table below summarizes all these methods of obtaining salts.
1. The interaction of acids and bases (neutralization reaction), for example:
Cu(OH) 2 + H 2 SO 4 = CuSO 4 + 2H 2 O
2. Interaction of the main or amphoteric oxides with acid oxides, for example:
BaO + CO 2 = BaCO 3 Cr 2 O 3 + 3SO 3 = Cr 2 (SO 4) 3
3. Interaction of basic or amphoteric oxides with acids, for example:
K 2 O + 2 HCl = 2 K Cl + H 2 O
ZnO + 2HNO) = Zn(NO 3) 2 + H 2 O
4. Interaction of bases with acid oxides, for example:
Ca(OH) 2 + N 2 O 6 = Ca(NO 3) 2 + H 2 O
5. Interaction of alkalis with salts, for example:
2LiOH + SnCl 2 = 2LiCl + Sn(OH) 2
6. Interaction of salts with acids, for example:
BaCl 2 + H 2 SO 4 = BaSO 4 + 2HC1
K 2 CO 3 + 2HC1 = 2KCl + CO 2 + H 2 O
7. Interaction of salts with each other, for example:
Na 2 CO 3 + BaCl 2 = BaCO 3 ↓ + 2NaCI
8. Interaction of salts with metals, for example:
CuCl 2 + Ni = NiCl 2 + Cu
9. Interaction of metals with acids.
When most acids (except HNO 3 and conc. H 2 SO 4) react with metals in the voltage range up to hydrogen, hydrogen is formed along with the salt, for example:
Al + 6HC1 = 2A1C1 3 + 3H 2
Nitric acid and conc. sulfuric acid, when interacting with metals, also forms salts, but instead of hydrogen, other products are formed.
Interaction of metals with non-metals. This method can be used to obtain salts of some oxygen-free acids, for example:
2Fe + 3C1 2 = 2FeCl 3
Specific methods of obtaining
1. Interaction of metals, the oxides and hydroxides of which are amphoteric, with alkalis. For example, when zinc is fused with potassium hydroxide, a salt is formed - potassium zincate:
Zn (tv.) + 2KON (tv.) = K 2 ZnO 2 + H 2
With an aqueous solution of alkali, zinc forms a complex salt - potassium tetrahydroxozincate:
Zn + 2KOH + 2H 2 O = K 2 + H 2
2. Fusion of salts with certain acid oxides.
In this case, the non-volatile acid oxide displaces the volatile acid oxide from the salt. For example:
K 2 CO 3 + SiO 2 = K 2 SiO 3 + CO 2
3. Interaction of alkalis with halogens, for example:
C1 2 + 2KON = KS1 + KClO + H 2 O
3C1 2 + 6KON = 5KS1 + KClO 3 + 3H 2 O
4. Interaction of metal halides with halogens. A more active halogen displaces a less active one from its salt solution, for example:
2KBr + Cl 2 = 2KCl + Br 2
Use of salts in medicine
Sodium chloride: If there is a deficiency of sodium chloride in the body, it is administered intravenously or subcutaneously in the form of a 0.9% aqueous solution, called isotonic. Its administration equalizes and normalizes the osmotic pressure of the blood. Hypertonic solutions of sodium chloride (3% now, 5%, 10%) are used externally for compresses and lotions in the treatment of purulent wounds. Due to the osmotic effect, these solutions promote the separation of pus from wounds. Sodium chloride is also used for baths, rubdowns, and rinses for diseases of the upper respiratory tract.
Potassium chloride: The main indication for the use of potassium chloride is cardiac arrhythmia, especially due to intoxication with cardiac glycosides, which is associated with depletion of myocardial cells in potassium ions.
Bromides used as sedatives. The calming effect of bromine preparations is based on their ability to enhance inhibitory processes in the cerebral cortex. Therefore, bromides are used for neurasthenia and increased irritability.
Yodides used as iodine carriers for hyperthyroidism and endemic goiter. If food or water does not contain enough iodine, as happens in some mountainous areas, the local population develops a disease - cretinism or goiter.
Potassium permanganate: Due to its strong oxidizing properties, it is used as a good disinfectant. Potassium permanganate is used as an antiseptic externally in aqueous solutions various concentrations for washing wounds, gargling, in gynecological practice, for skin burns.
Sodium thiosulfate: The use of sodium thiosulfate is based on its ability to release sulfur. The drug is used as an antidote for poisoning by halogens, cyanides and hydrocyanic acid. The drug can also be used for poisoning with arsenic, mercury, and lead compounds. Sodium thiosulfate is also used for allergic diseases, arthritis, and neuralgia intravenously in the form of a 30% aqueous solution.
Sodium sulfate: Glauber's salt is used in medicine for constipation, as a laxative orally, 15-30 g per dose. This salt can also be prescribed as an antidote for poisoning with lead salts, which produce insoluble precipitates.
Magnesium sulfate: taken orally for constipation, as a laxative, 15-30 g per dose. Taken as an antispasmodic for hypertension in the form of a 25% solution (subcutaneous); for pain relief during labor, 10-20 ml of a 25% solution intramuscularly; as an anticonvulsant; as a choleretic agent orally in the form of a 25% solution.
Magnesium carbonate: used as an astringent. Prescribed orally 1-3 g at increased acidity gastric juice and as a mild laxative. Included in tooth powders.
Sodium nitrite: used as a vasodilator for angina, migraine or subcutaneously. For subcutaneous injections it is usually used in ampoules in the form of a 1% solution. Sodium nitrite is also used in cyanide poisoning.
Sodium tetraborate: used in the form of a 1-2% solution for gargling, in ointments and powder.
Calcium ions 6 enhance the vital activity of cells, promote the contraction of skeletal muscles and heart muscles, they are necessary for the formation bone tissue, blood clotting occurs only in the presence of calcium ions. Calcium salts used in medicine are burnt calcium sulfate (in dental practice). Solutions of calcium salts relieve itching caused by an allergic condition, so they are classified as antiallergic substances.
Barium sulfate: insoluble in water, acids, or organic solvents, and therefore non-toxic. The use of BaSO 4 in medicine is based on its impermeability to x-rays, which is used in radiology to obtain contrast x-rays and for fluoroscopic examination of the digestive tract. It is taken in the form of barium gruel mixed with water. The stomach is filled with this mass to delay x-rays. After a certain time, it is completely eliminated from the body.
Zinc sulfate : has been used in medicine for a long time under the name white sulfate, which is explained by the fact that this salt is colorless, unlike copper and iron sulfate. It is used externally as an antiseptic and astringent in ophthalmic practice.
Literature:
Main sources:
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Additional sources:
1. Akhmetov N.S. "General and inorganic chemistry", M., graduate School, 2009.
2. Glinka N.L. " general chemistry", KnoRus, 2009.
3. Kuzmenko N.E., Eremin V.V. "The Beginnings of Chemistry". Modern course for applicants to universities., M., Exam, 2002.
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