Classification of inorganic substances with examples of compounds
Now let's analyze the classification scheme presented above in more detail.
As we see, first of all, all inorganic substances are divided into simple And complex:
Simple substances These are substances that are formed by atoms of only one chemical element. For example, simple substances are hydrogen H2, oxygen O2, iron Fe, carbon C, etc.
Among simple substances there are metals, nonmetals And noble gases:
Metals formed by chemical elements located below the boron-astatine diagonal, as well as all elements located in side groups.
Noble gases formed by chemical elements of group VIIIA.
Nonmetals are formed respectively by chemical elements located above the boron-astatine diagonal, with the exception of all elements of side subgroups and noble gases located in group VIIIA:
The names of simple substances most often coincide with the names chemical elements, the atoms of which they are formed. However, for many chemical elements the phenomenon of allotropy is widespread. Allotropy is the phenomenon when one chemical element is capable of forming several simple substances. For example, in the case of the chemical element oxygen, the existence of molecular compounds with the formulas O 2 and O 3 is possible. The first substance is usually called oxygen in the same way as the chemical element whose atoms it is formed, and the second substance (O 3) is usually called ozone. The simple substance carbon can mean any of its allotropic modifications, for example, diamond, graphite or fullerenes. The simple substance phosphorus can be understood as its allotropic modifications, such as white phosphorus, red phosphorus, black phosphorus.
Complex substances
Complex substances are substances formed by atoms of two or more chemical elements.
For example, complex substances are ammonia NH 3, sulfuric acid H 2 SO 4, slaked lime Ca (OH) 2 and countless others.
Among complex inorganic substances, there are 5 main classes, namely oxides, bases, amphoteric hydroxides, acids and salts:
Oxides - complex substances formed by two chemical elements, one of which is oxygen in the oxidation state -2.
The general formula of oxides can be written as E x O y, where E is the symbol of a chemical element.
Nomenclature of oxides
The name of the oxide of a chemical element is based on the principle:
For example:
Fe 2 O 3 - iron (III) oxide; CuO—copper(II) oxide; N 2 O 5 - nitric oxide (V)
You can often find information that the valency of an element is indicated in parentheses, but this is not the case. So, for example, the oxidation state of nitrogen N 2 O 5 is +5, and the valence, oddly enough, is four.
If a chemical element has a single positive oxidation state in compounds, then the oxidation state is not indicated. For example:
Na 2 O - sodium oxide; H 2 O - hydrogen oxide; ZnO - zinc oxide.
Oxides classification
Oxides, according to their ability to form salts when interacting with acids or bases, are divided accordingly into salt-forming And non-salt-forming.
There are few non-salt-forming oxides; they are all formed by nonmetals in the oxidation state +1 and +2. The list of non-salt-forming oxides should be remembered: CO, SiO, N 2 O, NO.
Salt-forming oxides, in turn, are divided into basic, acidic And amphoteric.
Basic oxides These are oxides that, when reacting with acids (or acid oxides), form salts. Basic oxides include metal oxides in the oxidation state +1 and +2, with the exception of the oxides BeO, ZnO, SnO, PbO.
Acidic oxides These are oxides that, when reacting with bases (or basic oxides), form salts. Acidic oxides are almost all oxides of non-metals with the exception of non-salt-forming CO, NO, N 2 O, SiO, as well as all metal oxides in high oxidation states (+5, +6 and +7).
Amphoteric oxides are called oxides that can react with both acids and bases, and as a result of these reactions form salts. Such oxides exhibit a dual acid-base nature, that is, they can exhibit the properties of both acidic and basic oxides. Amphoteric oxides include metal oxides in the oxidation states +3, +4, as well as the oxides BeO, ZnO, SnO, and PbO as exceptions.
Some metals can form all three types of salt-forming oxides. For example, chromium forms the basic oxide CrO, the amphoteric oxide Cr 2 O 3 and the acidic oxide CrO 3.
As you can see, the acid-base properties of metal oxides directly depend on the degree of oxidation of the metal in the oxide: than more degree oxidation, the more pronounced the acidic properties.
Reasons
Reasons - compounds with the formula Me(OH) x, where x most often equal to 1 or 2.
Classification of bases
Bases are classified according to the number of hydroxyl groups in one structural unit.
Bases with one hydroxo group, i.e. type MeOH is called monoacid bases, with two hydroxo groups, i.e. type Me(OH) 2, respectively, diacid etc.
Bases are also divided into soluble (alkalis) and insoluble.
Alkalies include exclusively hydroxides of alkali and alkaline earth metals, as well as thallium hydroxide TlOH.
Nomenclature of bases
The name of the foundation is based on the following principle:
For example:
Fe(OH) 2 - iron (II) hydroxide,
Cu(OH) 2 - copper (II) hydroxide.
In cases where the metal in complex substances has a constant oxidation state, it is not required to indicate it. For example:
NaOH - sodium hydroxide,
Ca(OH) 2 - calcium hydroxide, etc.
Acids
Acids - complex substances whose molecules contain hydrogen atoms that can be replaced by a metal.
The general formula of acids can be written as H x A, where H are hydrogen atoms that can be replaced by a metal, and A is the acidic residue.
For example, acids include compounds such as H2SO4, HCl, HNO3, HNO2, etc.
Classification of acids
According to the number of hydrogen atoms that can be replaced by a metal, acids are divided into:
- O base acids: HF, HCl, HBr, HI, HNO 3 ;
- d basic acids: H 2 SO 4, H 2 SO 3, H 2 CO 3;
- T rehobasic acids: H 3 PO 4 , H 3 BO 3 .
It should be noted that the number of hydrogen atoms in the case of organic acids most often does not reflect their basicity. For example, acetic acid with the formula CH 3 COOH, despite the presence of 4 hydrogen atoms in the molecule, is not tetra- but monobasic. The basicity of organic acids is determined by the number of carboxyl groups (-COOH) in the molecule.
Also, based on the presence of oxygen in the molecules, acids are divided into oxygen-free (HF, HCl, HBr, etc.) and oxygen-containing (H 2 SO 4, HNO 3, H 3 PO 4, etc.). Oxygen-containing acids are also called oxoacids.
You can read more about the classification of acids.
Nomenclature of acids and acid residues
The following list of names and formulas of acids and acid residues is a must-learn.
In some cases, a number of the following rules can make memorization easier.
As can be seen from the table above, the construction of systematic names of oxygen-free acids is as follows:
For example:
HF—hydrofluoric acid;
HCl—hydrochloric acid;
H 2 S is hydrosulfide acid.
The names of acidic residues of oxygen-free acids are based on the principle:
For example, Cl - - chloride, Br - - bromide.
The names of oxygen-containing acids are obtained by adding various suffixes and endings to the name of the acid-forming element. For example, if the acid-forming element in an oxygen-containing acid has the highest oxidation state, then the name of such an acid is constructed as follows:
For example, sulfuric acid H 2 S +6 O 4, chromic acid H 2 Cr +6 O 4.
All oxygen-containing acids can also be classified as acid hydroxides because they contain hydroxyl groups (OH). For example, this can be seen from the following graphical formulas of some oxygen-containing acids:
Thus, sulfuric acid can otherwise be called sulfur(VI) hydroxide, Nitric acid- nitrogen hydroxide (V), phosphoric acid - phosphorus hydroxide (V), etc. In this case, the number in brackets characterizes the degree of oxidation of the acid-forming element. This variant of the names of oxygen-containing acids may seem extremely unusual to many, but occasionally such names can be found in real CMMs Unified State Exam in chemistry in tasks on the classification of inorganic substances.
Amphoteric hydroxides
Amphoteric hydroxides - metal hydroxides exhibiting a dual nature, i.e. capable of exhibiting both the properties of acids and the properties of bases.
Metal hydroxides in oxidation states +3 and +4 are amphoteric (as are oxides).
Also, as exceptions, amphoteric hydroxides include the compounds Be(OH) 2, Zn(OH) 2, Sn(OH) 2 and Pb(OH) 2, despite the oxidation state of the metal in them +2.
For amphoteric hydroxides of tri- and tetravalent metals, the existence of ortho- and meta-forms is possible, differing from each other by one water molecule. For example, aluminum(III) hydroxide can exist in the ortho form Al(OH)3 or the meta form AlO(OH) (metahydroxide).
Since, as already mentioned, amphoteric hydroxides exhibit both the properties of acids and the properties of bases, their formula and name can also be written differently: either as a base or as an acid. For example:
Salts
For example, salts include compounds such as KCl, Ca(NO 3) 2, NaHCO 3, etc.
The definition presented above describes the composition of most salts, however, there are salts that do not fall under it. For example, instead of metal cations, the salt may contain ammonium cations or its organic derivatives. Those. salts include compounds such as, for example, (NH 4) 2 SO 4 (ammonium sulfate), + Cl - (methyl ammonium chloride), etc.
Classification of salts
On the other hand, salts can be considered as products of the replacement of hydrogen cations H + in an acid with other cations, or as products of the replacement of hydroxide ions in bases (or amphoteric hydroxides) with other anions.
With complete replacement, the so-called average or normal salt. For example, with complete replacement of hydrogen cations in sulfuric acid with sodium cations, an average (normal) salt Na 2 SO 4 is formed, and with complete replacement of hydroxide ions in the base Ca (OH) 2 with acidic residues of nitrate ions, an average (normal) salt is formed Ca(NO3)2.
Salts obtained by incomplete replacement of hydrogen cations in a dibasic (or more) acid with metal cations are called acidic. Thus, when hydrogen cations in sulfuric acid are incompletely replaced by sodium cations, the acid salt NaHSO 4 is formed.
Salts that are formed by incomplete replacement of hydroxide ions in two-acid (or more) bases are called bases. O strong salts. For example, with incomplete replacement of hydroxide ions in the base Ca(OH) 2 with nitrate ions, a base is formed O clear salt Ca(OH)NO3.
Salts consisting of cations of two different metals and anions of acidic residues of only one acid are called double salts. So, for example, double salts are KNaCO 3, KMgCl 3, etc.
If a salt is formed by one type of cations and two types of acid residues, such salts are called mixed. For example, mixed salts are the compounds Ca(OCl)Cl, CuBrCl, etc.
There are salts that do not fall under the definition of salts as products of the replacement of hydrogen cations in acids with metal cations or products of the replacement of hydroxide ions in bases with anions of acidic residues. These are complex salts. For example, complex salts are sodium tetrahydroxozincate and tetrahydroxoaluminate with the formulas Na 2 and Na, respectively. Complex salts can most often be recognized among others by the presence of square brackets in the formula. However, you need to understand that in order for a substance to be classified as a salt, it must contain some cations other than (or instead of) H +, and the anions must contain some anions other than (or instead of) OH -. So, for example, the compound H2 does not belong to the class of complex salts, since when it dissociates from cations, only hydrogen cations H + are present in the solution. Based on the type of dissociation, this substance should rather be classified as an oxygen-free complex acid. Likewise, the OH compound does not belong to salts, because this compound consists of cations + and hydroxide ions OH -, i.e. it should be considered a comprehensive foundation.
Nomenclature of salts
Nomenclature of medium and acid salts
The name of medium and acid salts is based on the principle:
If the oxidation state of a metal in complex substances is constant, then it is not indicated.
The names of acid residues were given above when considering the nomenclature of acids.
For example,
Na 2 SO 4 - sodium sulfate;
NaHSO 4 - sodium hydrogen sulfate;
CaCO 3 - calcium carbonate;
Ca(HCO 3) 2 - calcium bicarbonate, etc.
Nomenclature of basic salts
The names of the main salts are based on the principle:
For example:
(CuOH) 2 CO 3 - copper (II) hydroxycarbonate;
Fe(OH) 2 NO 3 - iron (III) dihydroxonitrate.
Nomenclature of complex salts
The nomenclature of complex compounds is much more complex, and for passing the Unified State Exam You don’t need to know much about the nomenclature of complex salts.
You should be able to name complex salts obtained by reacting alkali solutions with amphoteric hydroxides. For example:
*The same colors in the formula and name indicate the corresponding elements of the formula and name.
Trivial names of inorganic substances
By trivial names we mean the names of substances that are not related, or weakly related, to their composition and structure. Trivial names are determined, as a rule, either historical reasons or the physical or chemical properties of these compounds.
List of trivial names of inorganic substances that you need to know:
| Na 3 | cryolite |
| SiO2 | quartz, silica |
| FeS 2 | pyrite, iron pyrite |
| CaSO 4 ∙2H 2 O | gypsum |
| CaC2 | calcium carbide |
| Al 4 C 3 | aluminum carbide |
| KOH | caustic potassium |
| NaOH | caustic soda, caustic soda |
| H2O2 | hydrogen peroxide |
| CuSO 4 ∙5H 2 O | copper sulfate |
| NH4Cl | ammonia |
| CaCO3 | chalk, marble, limestone |
| N2O | laughing gas |
| NO 2 | brown gas |
| NaHCO3 | baking (drinking) soda |
| Fe3O4 | iron scale |
| NH 3 ∙H 2 O (NH 4 OH) | ammonia |
| CO | carbon monoxide |
| CO2 | carbon dioxide |
| SiC | carborundum (silicon carbide) |
| PH 3 | phosphine |
| NH 3 | ammonia |
| KClO3 | Bertholet's salt (potassium chlorate) |
| (CuOH)2CO3 | malachite |
| CaO | quicklime |
| Ca(OH)2 | slaked lime |
| transparent aqueous solution of Ca(OH) 2 | lime water |
| suspension of solid Ca(OH) 2 in its aqueous solution | lime milk |
| K2CO3 | potash |
| Na 2 CO 3 | soda ash |
| Na 2 CO 3 ∙10H 2 O | crystal soda |
| MgO | magnesia |
Acids are chemical compounds that are capable of donating an electrically charged hydrogen ion (cation) and also accepting two interacting electrons, resulting in the formation of a covalent bond.
In this article we will look at the main acids that are studied in middle school. secondary schools, and also learn many interesting facts about a variety of acids. Let's get started.
Acids: types
In chemistry, there are many different acids that have very different properties. Chemists distinguish acids by their oxygen content, volatility, solubility in water, strength, stability, and whether they belong to the organic or inorganic class of chemical compounds. In this article we will look at a table that presents the most famous acids. The table will help you remember the name of the acid and its chemical formula.
So, everything is clearly visible. This table presents the most famous chemical industry acids. The table will help you remember names and formulas much faster.
Hydrogen sulfide acid
H 2 S is hydrosulfide acid. Its peculiarity lies in the fact that it is also a gas. Hydrogen sulfide is very poorly soluble in water, and also interacts with many metals. Hydrogen sulfide acid belongs to the group of “weak acids”, examples of which we will consider in this article.
H 2 S has a slightly sweet taste and also a very strong rotten egg smell. In nature, it can be found in natural or volcanic gases, and it is also released during protein decay.
The properties of acids are very diverse; even if an acid is indispensable in industry, it can be very harmful to human health. This acid is very toxic to humans. When a small amount of hydrogen sulfide is inhaled, a person experiences a headache, severe nausea and dizziness. If a person inhales a large number of H 2 S, it can lead to seizures, coma or even instant death.
Sulfuric acid
H 2 SO 4 is a strong sulfuric acid, which children are introduced to in chemistry lessons in the 8th grade. Chemical acids such as sulfuric acid are very strong oxidizing agents. H 2 SO 4 acts as an oxidizing agent on many metals, as well as basic oxides.
H 2 SO 4 causes chemical burns when it comes into contact with skin or clothing, but it is not as toxic as hydrogen sulfide.
Nitric acid
Strong acids are very important in our world. Examples of such acids: HCl, H 2 SO 4, HBr, HNO 3. HNO 3 is a well-known nitric acid. It has found wide application in industry, as well as in agriculture. It is used to make various fertilizers, in jewelry, when printing photographs, in manufacturing medicines and dyes, as well as in the military industry.
Such chemical acids, like nitrogen, are very harmful to the body. HNO 3 vapors leave ulcers, cause acute inflammation and irritation of the respiratory tract.
Nitrous acid
Nitrous acid is often confused with nitric acid, but there is a difference between them. The fact is that it is much weaker than nitrogen, it has completely different properties and effects on the human body.
HNO 2 has found wide application in the chemical industry.
Hydrofluoric acid
Hydrofluoric acid (or hydrogen fluoride) is a solution of H 2 O with HF. The acid formula is HF. Hydrofluoric acid is very actively used in the aluminum industry. It is used to dissolve silicates, etch silicon and silicate glass.
Hydrogen fluoride is very harmful to the human body and, depending on its concentration, can be a mild narcotic. If it comes into contact with the skin, at first there are no changes, but after a few minutes a sharp pain and chemical burn may appear. Hydrofluoric acid is very harmful to the environment.
Hydrochloric acid
HCl is hydrogen chloride and is a strong acid. Hydrogen chloride retains the properties of acids belonging to the group of strong acids. The acid is transparent and colorless in appearance, but smokes in air. Hydrogen chloride is widely used in the metallurgical and food industries.
This acid causes chemical burns, but getting into the eyes is especially dangerous.
Phosphoric acid
Phosphoric acid (H 3 PO 4) is a weak acid in its properties. But even weak acids can have the properties of strong ones. For example, H 3 PO 4 is used in industry to restore iron from rust. In addition, phosphoric (or orthophosphoric) acid is widely used in agriculture - many different fertilizers are made from it.
The properties of acids are very similar - almost each of them is very harmful to the human body, H 3 PO 4 is no exception. For example, this acid also causes severe chemical burns, nosebleeds, and chipping of teeth.
Carbonic acid
H 2 CO 3 is a weak acid. It is obtained by dissolving CO 2 (carbon dioxide) in H 2 O (water). Carbonic acid is used in biology and biochemistry.
Density of various acids
The density of acids occupies an important place in the theoretical and practical parts chemistry. By knowing the density, you can determine the concentration of a particular acid, solve chemical calculation problems, and add the correct amount of acid to complete the reaction. The density of any acid changes depending on the concentration. For example, the higher the concentration percentage, the higher the density.
General properties of acids
Absolutely all acids are (that is, they consist of several elements of the periodic table), and they necessarily include H (hydrogen) in their composition. Next we will look at which are common:
- All oxygen-containing acids (in the formula of which O is present) form water upon decomposition, and also oxygen-free ones decompose into simple substances (for example, 2HF decomposes into F 2 and H 2).
- Oxidizing acids react with all metals in the metal activity series (only those to the left of H).
- They interact with various salts, but only with those that were formed by an even weaker acid.
According to their own physical properties acids differ sharply from each other. After all, they can have a smell or not, and also be in a variety of different states of aggregation: liquid, gaseous and even solid. Solid acids are very interesting to study. Examples of such acids: C 2 H 2 0 4 and H 3 BO 3.
Concentration
Concentration is a value that determines the quantitative composition of any solution. For example, chemists often need to determine how much pure sulfuric acid is present in dilute acid H 2 SO 4. To do this, they pour a small amount of dilute acid into a measuring cup, weigh it, and determine the concentration using a density chart. The concentration of acids is closely related to density; often, when determining the concentration, there are calculation problems where you need to determine the percentage of pure acid in a solution.
Classification of all acids according to the number of H atoms in their chemical formula
One of the most popular classifications is the division of all acids into monobasic, dibasic and, accordingly, tribasic acids. Examples of monobasic acids: HNO 3 (nitric), HCl (hydrochloric), HF (hydrofluoric) and others. These acids are called monobasic, since they contain only one H atom. There are many such acids, it is impossible to remember absolutely every one. You just need to remember that acids are classified according to the number of H atoms in their composition. Dibasic acids are defined similarly. Examples: H 2 SO 4 (sulphuric), H 2 S (hydrogen sulfide), H 2 CO 3 (coal) and others. Tribasic: H 3 PO 4 (phosphoric).
Basic classification of acids
One of the most popular classifications of acids is their division into oxygen-containing and oxygen-free. How to remember, without knowing the chemical formula of a substance, that it is an oxygen-containing acid?
All oxygen-free acids lack the important element O - oxygen, but they do contain H. Therefore, the word “hydrogen” is always attached to their name. HCl is a H 2 S - hydrogen sulfide.
But you can also write a formula based on the names of acid-containing acids. For example, if the number of O atoms in a substance is 4 or 3, then the suffix -n-, as well as the ending -aya-, is always added to the name:
- H 2 SO 4 - sulfur (number of atoms - 4);
- H 2 SiO 3 - silicon (number of atoms - 3).
If the substance has less than three oxygen atoms or three, then the suffix -ist- is used in the name:
- HNO 2 - nitrogenous;
- H 2 SO 3 - sulfurous.
General properties
All acids taste sour and often slightly metallic. But there are other similar properties that we will now consider.
There are substances called indicators. The indicators change their color, or the color remains, but its shade changes. This occurs when the indicators are affected by other substances, such as acids.
An example of a color change is such a familiar product as tea and citric acid. When lemon is added to tea, the tea gradually begins to noticeably brighten. This is due to the fact that lemon contains citric acid.
There are other examples. Litmus, which in a neutral environment has a lilac color, when added of hydrochloric acid turns red.
When the tensions are in the tension series before hydrogen, gas bubbles are released - H. However, if a metal that is in the tension series after H is placed in a test tube with acid, then no reaction will occur, there will be no gas evolution. So, copper, silver, mercury, platinum and gold will not react with acids.
In this article we examined the most famous chemical acids, as well as their main properties and differences.
Do not underestimate the role of acids in our lives, because many of them are simply irreplaceable in Everyday life. First, let's remember what acids are. These are complex substances. The formula is written as follows: HnA, where H is hydrogen, n is the number of atoms, A is the acid residue.
The main properties of acids include the ability to replace molecules of hydrogen atoms with metal atoms. Most of them are not only caustic, but also very poisonous. But there are also those that we encounter constantly, without harm to our health: vitamin C, citric acid, lactic acid. Let's consider the basic properties of acids.
Physical properties
The physical properties of acids often provide clues to their character. Acids can exist in three forms: solid, liquid and gaseous. For example: nitric (HNO3) and sulfuric acid (H2SO4) are colorless liquids; boric (H3BO3) and metaphosphoric (HPO3) are solid acids. Some of them have color and smell. Different acids dissolve differently in water. There are also insoluble ones: H2SiO3 - silicon. Liquid substances have a sour taste. Some acids are named after the fruits in which they are found: malic acid, citric acid. Others get their name from the chemical elements they contain.
Classification of acids
Acids are usually classified according to several criteria. The very first one is based on the oxygen content in them. Namely: oxygen-containing (HClO4 - chlorine) and oxygen-free (H2S - hydrogen sulfide).
By number of hydrogen atoms (by basicity):
- Monobasic – contains one hydrogen atom (HMnO4);
- Dibasic – has two hydrogen atoms (H2CO3);
- Tribasic, accordingly, have three hydrogen atoms (H3BO);
- Polybasic - have four or more atoms, are rare (H4P2O7).
According to the classes of chemical compounds, they are divided into organic and inorganic acids. The former are mainly found in products of plant origin: acetic, lactic, nicotinic, ascorbic acids. TO inorganic acids include: sulfur, nitrogen, boron, arsenic. The range of their applications is quite wide, from industrial needs (production of dyes, electrolytes, ceramics, fertilizers, etc.) to cooking or cleaning sewers. Acids can also be classified by strength, volatility, stability and solubility in water.
Chemical properties
Let's look at the main Chemical properties acids
- The first is interaction with indicators. Litmus, methyl orange, phenolphthalein and universal indicator paper are used as indicators. In acid solutions, the color of the indicator will change color: litmus and universal ind. the paper will turn red, methyl orange will turn pink, phenolphthalein will remain colorless.
- The second is the interaction of acids with bases. This reaction is also called neutralization. An acid reacts with a base, resulting in salt + water. For example: H2SO4+Ca(OH)2=CaSO4+2 H2O.
- Since almost all acids are highly soluble in water, neutralization can be carried out with both soluble and insoluble bases. The exception is silicic acid, which is almost insoluble in water. To neutralize it, bases such as KOH or NaOH are required (they are soluble in water).
- The third is the interaction of acids with basic oxides. A neutralization reaction also occurs here. Basic oxides are close “relatives” of bases, therefore the reaction is the same. We use these very often oxidizing properties acids For example, to remove rust from pipes. The acid reacts with the oxide to form a soluble salt.
- Fourth - reaction with metals. Not all metals react equally well with acids. They are divided into active (K, Ba, Ca, Na, Mg, Al, Mn, Zn, Cr, Fe, Ni, Sn. Pb) and inactive (Cu, Hg, Ag, Pt, Au). It is also worth paying attention to the strength of the acid (strong, weak). For example, salt and sulfuric acid are able to react with all inactive metals, and citric and oxalic acids are so weak that they react very slowly even with active metals.
- Fifth, the reaction of oxygen-containing acids to heating. Almost all acids in this group decompose when heated into oxygen oxide and water. The exceptions are carbonic acid (H3PO4) and sulfurous acid (H2SO4). When heated, they break down into water and gas. This must be remembered. That's all the basic properties of acids.
These are substances that dissociate in solutions to form hydrogen ions.
Acids are classified by their strength, by their basicity, and by the presence or absence of oxygen in the acid.
By strengthacids are divided into strong and weak. The most important strong acids are nitric HNO 3, sulfuric H2SO4, and hydrochloric HCl.
According to the presence of oxygen distinguish between oxygen-containing acids ( HNO3, H3PO4 etc.) and oxygen-free acids ( HCl, H 2 S, HCN, etc.).
By basicity, i.e. According to the number of hydrogen atoms in an acid molecule that can be replaced by metal atoms to form a salt, acids are divided into monobasic (for example, HNO 3, HCl), dibasic (H 2 S, H 2 SO 4), tribasic (H 3 PO 4), etc.
The names of oxygen-free acids are derived from the name of the non-metal with the addition of the ending -hydrogen: HCl - hydrochloric acid, H2S e - hydroselenic acid, HCN - hydrocyanic acid.
The names of oxygen-containing acids are also formed from the Russian name of the corresponding element with the addition of the word “acid”. In this case, the name of the acid in which the element is in the highest oxidation state ends in “naya” or “ova”, for example, H2SO4 - sulfuric acid, HClO4 - perchloric acid, H3AsO4 - arsenic acid. With a decrease in the oxidation degree of the acid-forming element, the endings change in the following sequence: “ovate” ( HClO3 - perchloric acid), “solid” ( HClO2 - chlorous acid), “ovate” ( H O Cl - hypochlorous acid). If an element forms acids while being in only two oxidation states, then the name of the acid corresponding to the lowest oxidation state of the element receives the ending “iste” ( HNO3 - Nitric acid, HNO2 - nitrous acid).
Table - The most important acids and their salts
|
Acid |
Names of the corresponding normal salts |
|
|
Name |
Formula |
|
|
Nitrogen |
HNO3 |
Nitrates |
|
Nitrogenous |
HNO2 |
Nitrites |
|
Boric (orthoboric) |
H3BO3 |
Borates (orthoborates) |
|
Hydrobromic |
Bromides |
|
|
Hydroiodide |
Iodides |
|
|
Silicon |
H2SiO3 |
Silicates |
|
Manganese |
HMnO4 |
Permanganates |
|
Metaphosphoric |
HPO 3 |
Metaphosphates |
|
Arsenic |
H3AsO4 |
Arsenates |
|
Arsenic |
H3AsO3 |
Arsenites |
|
Orthophosphoric |
H3PO4 |
Orthophosphates (phosphates) |
|
Diphosphoric (pyrophosphoric) |
H4P2O7 |
Diphosphates (pyrophosphates) |
|
Dichrome |
H2Cr2O7 |
Dichromats |
|
Sulfuric |
H2SO4 |
Sulfates |
|
Sulphurous |
H2SO3 |
Sulfites |
|
Coal |
H2CO3 |
Carbonates |
|
Phosphorous |
H3PO3 |
Phosphites |
|
Hydrofluoric (fluoric) |
Fluorides |
|
|
Hydrochloric (salt) |
Chlorides |
|
|
Chlorine |
HClO4 |
Perchlorates |
|
Chlorous |
HClO3 |
Chlorates |
|
Hypochlorous |
HClO |
Hypochlorites |
|
Chrome |
H2CrO4 |
Chromates |
|
Hydrogen cyanide (cyanic) |
Cyanide |
|
Obtaining acids
1. Oxygen-free acids can be obtained by direct combination of non-metals with hydrogen:
H 2 + Cl 2 → 2HCl,
H 2 + S H 2 S.
2. Oxygen-containing acids can often be obtained by directly combining acid oxides with water:
SO 3 + H 2 O = H 2 SO 4,
CO 2 + H 2 O = H 2 CO 3,
P 2 O 5 + H 2 O = 2 HPO 3.
3. Both oxygen-free and oxygen-containing acids can be obtained by exchange reactions between salts and other acids:
BaBr 2 + H 2 SO 4 = BaSO 4 + 2HBr,
CuSO 4 + H 2 S = H 2 SO 4 + CuS,
CaCO 3 + 2HBr = CaBr 2 + CO 2 + H 2 O.
4. In some cases, redox reactions can be used to produce acids:
H 2 O 2 + SO 2 = H 2 SO 4,
3P + 5HNO3 + 2H2O = 3H3PO4 + 5NO.
Chemical properties of acids
1. The most characteristic chemical property of acids is their ability to react with bases (as well as basic and amphoteric oxides) to form salts, for example:
H 2 SO 4 + 2NaOH = Na 2 SO 4 + 2H 2 O,
2HNO 3 + FeO = Fe(NO 3) 2 + H 2 O,
2 HCl + ZnO = ZnCl 2 + H 2 O.
2. The ability to interact with some metals in the voltage series up to hydrogen, with the release of hydrogen:
Zn + 2HCl = ZnCl 2 + H 2,
2Al + 6HCl = 2AlCl3 + 3H2.
3. With salts, if a slightly soluble salt or volatile substance is formed:
H 2 SO 4 + BaCl 2 = BaSO 4 ↓ + 2HCl,
2HCl + Na 2 CO 3 = 2NaCl + H 2 O + CO 2,
2KHCO 3 + H 2 SO 4 = K 2 SO 4 +2SO 2+ 2H 2 O.
Note that polybasic acids dissociate stepwise, and the ease of dissociation at each step decreases; therefore, for polybasic acids, instead of medium salts, acidic salts are often formed (in the case of an excess of the reacting acid):
Na 2 S + H 3 PO 4 = Na 2 HPO 4 + H 2 S,
NaOH + H 3 PO 4 = NaH 2 PO 4 + H 2 O.
4. A special case of acid-base interaction is the reaction of acids with indicators, leading to a change in color, which has long been used for the qualitative detection of acids in solutions. So, litmus changes color in an acidic environment to red.
5. When heated, oxygen-containing acids decompose into oxide and water (preferably in the presence of a water-removing agent P2O5):
H 2 SO 4 = H 2 O + SO 3,
H 2 SiO 3 = H 2 O + SiO 2.
M.V. Andryukhova, L.N. Borodina