Acids are complex substances whose molecules include hydrogen atoms that can be replaced or exchanged for metal atoms and an acid residue.
Based on the presence or absence of oxygen in the molecule, acids are divided into oxygen-containing(H 2 SO 4 sulfuric acid, H 2 SO 3 sulfurous acid, HNO 3 nitric acid, H 3 PO 4 phosphoric acid, H 2 CO 3 carbonic acid, H 2 SiO 3 silicic acid) and oxygen-free(HF hydrofluoric acid, HCl hydrochloric acid (hydrochloric acid), HBr hydrobromic acid, HI hydroiodic acid, H 2 S hydrosulfide acid).
Depending on the number of hydrogen atoms in the acid molecule, acids are monobasic (with 1 H atom), dibasic (with 2 H atoms) and tribasic (with 3 H atoms). For example, nitric acid HNO 3 is monobasic, since its molecule contains one hydrogen atom, sulfuric acid H 2 SO 4 – dibasic, etc.
There are very few inorganic compounds containing four hydrogen atoms that can be replaced by a metal.
The part of an acid molecule without hydrogen is called an acid residue.
Acidic residues may consist of one atom (-Cl, -Br, -I) - these are simple acidic residues, or they may consist of a group of atoms (-SO 3, -PO 4, -SiO 3) - these are complex residues.
In aqueous solutions, during exchange and substitution reactions, acidic residues are not destroyed:
H 2 SO 4 + CuCl 2 → CuSO 4 + 2 HCl
The word anhydride means anhydrous, that is, an acid without water. For example,
H 2 SO 4 – H 2 O → SO 3. Anoxic acids do not have anhydrides.
Acids get their name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H 2 SO 4 - sulfuric; H 2 SO 3 – coal; H 2 SiO 3 – silicon, etc.
The element can form several oxygen acids. In this case, the indicated endings in the names of acids will be when the element exhibits a higher valence (the acid molecule contains a high content of oxygen atoms). If the element exhibits a lower valence, the ending in the name of the acid will be “empty”: HNO 3 - nitric, HNO 2 - nitrogenous.
Acids can be obtained by dissolving anhydrides in water. If the anhydrides are insoluble in water, the acid can be obtained by the action of another stronger acid on the salt of the required acid. This method is typical for both oxygen and oxygen-free acids. Oxygen-free acids are also obtained by direct synthesis from hydrogen and a non-metal, followed by dissolving the resulting compound in water:
H 2 + Cl 2 → 2 HCl;
H 2 + S → H 2 S.
Solutions of the resulting gaseous substances HCl and H 2 S are acids.
Under normal conditions, acids exist in both liquid and solid states.
Chemical properties of acids
Acid solutions act on indicators. All acids (except silicic) are highly soluble in water. Special substances - indicators allow you to determine the presence of acid.
Indicators are substances of complex structure. They change color depending on their interaction with different chemicals. In neutral solutions they have one color, in solutions of bases they have another color. When interacting with an acid, they change their color: the methyl orange indicator turns red, and the litmus indicator also turns red.
Interact with bases with the formation of water and salt, which contains an unchanged acid residue (neutralization reaction):
H 2 SO 4 + Ca(OH) 2 → CaSO 4 + 2 H 2 O.
Interact with base oxides with the formation of water and salt (neutralization reaction). The salt contains the acid residue of the acid that was used in the neutralization reaction:
H 3 PO 4 + Fe 2 O 3 → 2 FePO 4 + 3 H 2 O.
Interact with metals.
For acids to interact with metals, certain conditions must be met:
1. the metal must be sufficiently active with respect to acids (in the series of activity of metals it must be located before hydrogen). The further to the left a metal is in the activity series, the more intensely it interacts with acids;
2. the acid must be strong enough (that is, capable of donating hydrogen ions H +).
When leaking chemical reactions acids with metals, a salt is formed and hydrogen is released (except for the interaction of metals with nitric and concentrated sulfuric acids):
Zn + 2HCl → ZnCl 2 + H 2 ;
Cu + 4HNO 3 → CuNO 3 + 2 NO 2 + 2 H 2 O.
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| Acid formulas | Names of acids | Names of the corresponding salts |
| HClO4 | chlorine | perchlorates |
| HClO3 | hypochlorous | chlorates |
| HClO2 | chloride | chlorites |
| HClO | hypochlorous | hypochlorites |
| H5IO6 | iodine | periodates |
| HIO 3 | iodic | iodates |
| H2SO4 | sulfuric | sulfates |
| H2SO3 | sulfurous | sulfites |
| H2S2O3 | thiosulfur | thiosulfates |
| H2S4O6 | tetrathionic | tetrathionates |
| HNO3 | nitrogen | nitrates |
| HNO2 | nitrogenous | nitrites |
| H3PO4 | orthophosphoric | orthophosphates |
| HPO 3 | metaphosphoric | metaphosphates |
| H3PO3 | phosphorous | phosphites |
| H3PO2 | phosphorous | hypophosphites |
| H2CO3 | coal | carbonates |
| H2SiO3 | silicon | silicates |
| HMnO4 | manganese | permanganates |
| H2MnO4 | manganese | manganates |
| H2CrO4 | chrome | chromates |
| H2Cr2O7 | dichrome | dichromats |
| HF | hydrogen fluoride (fluoride) | fluorides |
| HCl | hydrochloric (hydrochloric) | chlorides |
| HBr | hydrobromic | bromides |
| HI | hydrogen iodide | iodides |
| H2S | hydrogen sulfide | sulfides |
| HCN | hydrogen cyanide | cyanides |
| HOCN | cyan | cyanates |
Let me briefly remind you of specific examples how to properly call salts.
Example 1. The salt K 2 SO 4 is formed by a sulfuric acid residue (SO 4) and metal K. Salts of sulfuric acid are called sulfates. K 2 SO 4 - potassium sulfate.
Example 2. FeCl 3 - the salt contains iron and the remainder of hydrochloric acid(Cl). Name of salt: iron (III) chloride. Please note: in in this case we must not only name the metal, but also indicate its valency (III). In the previous example, this was not necessary, since the valency of sodium is constant.
Important: the name of the salt should indicate the valence of the metal only if the metal has a variable valency!
Example 3. Ba(ClO) 2 - the salt contains barium and the remainder of hypochlorous acid (ClO). Salt name: barium hypochlorite. The valency of the metal Ba in all its compounds is two; it does not need to be indicated.
Example 4. (NH 4) 2 Cr 2 O 7. The NH 4 group is called ammonium, the valence of this group is constant. Name of salt: ammonium dichromate (dichromate).
In the above examples we only encountered the so-called. medium or normal salts. Acidic, basic, double and complex salts, salts of organic acids will not be discussed here.
If you are interested not only in the nomenclature of salts, but also in the methods of their preparation and Chemical properties, I recommend turning to the relevant sections of the chemistry reference book: "
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 acids in the chemical industry. 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 pungent odor rotten eggs. 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 awakens headache, begins 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.
Chemical acids such as nitric acid 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 of 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 acids 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 located 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 the 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 chemical formula substances that are oxygen-containing acid?
All oxygen-free acids do not contain important element O is oxygen, but it contains 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 lemon 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 purple colour turns red when hydrochloric acid is added.
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.
| Acid formula | Acid name | Name of salt | Corresponding oxide |
| HCl | Solyanaya | Chlorides | ---- |
| HI | Hydroiodic | Iodides | ---- |
| HBr | Hydrobromic | Bromides | ---- |
| HF | Fluorescent | Fluorides | ---- |
| HNO3 | Nitrogen | Nitrates | N2O5 |
| H2SO4 | Sulfuric | Sulfates | SO 3 |
| H2SO3 | Sulphurous | Sulfites | SO 2 |
| H2S | Hydrogen sulfide | Sulfides | ---- |
| H2CO3 | Coal | Carbonates | CO2 |
| H2SiO3 | Silicon | Silicates | SiO2 |
| HNO2 | Nitrogenous | Nitrites | N2O3 |
| H3PO4 | Phosphorus | Phosphates | P2O5 |
| H3PO3 | Phosphorous | Phosphites | P2O3 |
| H2CrO4 | Chrome | Chromates | CrO3 |
| H2Cr2O7 | Two-chrome | Bichromates | CrO3 |
| HMnO4 | Manganese | Permanganates | Mn2O7 |
| HClO4 | Chlorine | Perchlorates | Cl2O7 |
Acids can be obtained in the laboratory:
1) when dissolving acid oxides in water:
N 2 O 5 + H 2 O → 2HNO 3;
CrO 3 + H 2 O → H 2 CrO 4 ;
2) when salts interact with strong acids:
Na 2 SiO 3 + 2HCl → H 2 SiO 3 ¯ + 2NaCl;
Pb(NO 3) 2 + 2HCl → PbCl 2 ¯ + 2HNO 3.
Acids interact with metals, bases, basic and amphoteric oxides, amphoteric hydroxides and salts:
Zn + 2HCl → ZnCl 2 + H 2 ;
Cu + 4HNO 3 (concentrated) → Cu(NO 3) 2 + 2NO 2 + 2H 2 O;
H 2 SO 4 + Ca(OH) 2 → CaSO 4 ¯ + 2H 2 O;
2HBr + MgO → MgBr 2 + H 2 O;
6HI + Al 2 O 3 → 2AlBr 3 + 3H 2 O;
H 2 SO 4 + Zn(OH) 2 → ZnSO 4 + 2H 2 O;
AgNO 3 + HCl → AgCl¯ + HNO 3 .
Typically, acids react only with those metals that come before hydrogen in the electrochemical voltage series, and free hydrogen is released. Such acids do not interact with low-active metals (voltages come after hydrogen in the electrochemical series). Acids, which are strong oxidizing agents (nitric, concentrated sulfuric), react with all metals, with the exception of noble ones (gold, platinum), but in this case it is not hydrogen that is released, but water and an oxide, for example, SO 2 or NO 2.
A salt is the product of replacing hydrogen in an acid with a metal.
All salts are divided into:
average– NaCl, K 2 CO 3, KMnO 4, Ca 3 (PO 4) 2, etc.;
sour– NaHCO 3, KH 2 PO 4;
main – CuOHCl, Fe(OH) 2 NO 3.
A middle salt is the product of complete replacement of hydrogen ions in an acid molecule with metal atoms.
Acidic salts contain hydrogen atoms that can participate in chemical exchange reactions. In acidic salts, incomplete replacement of hydrogen atoms with metal atoms occurred.
Basic salts are the product of incomplete replacement of hydroxo groups of polyvalent metal bases with acidic residues. Basic salts always contain a hydroxo group.
Medium salts are obtained by the interaction:
1) acids and bases:
NaOH + HCl → NaCl + H 2 O;
2) acid and basic oxide:
H 2 SO 4 + CaO → CaSO 4 ¯ + H 2 O;
3) acid oxide and reasons:
SO 2 + 2KOH → K 2 SO 3 + H 2 O;
4) acidic and basic oxides:
MgO + CO 2 → MgCO 3 ;
5) metal with acid:
Fe + 6HNO 3 (concentrated) → Fe(NO 3) 3 + 3NO 2 + 3H 2 O;
6) two salts:
AgNO 3 + KCl → AgCl¯ + KNO 3 ;
7) salts and acids:
Na 2 SiO 3 + 2HCl → 2NaCl + H 2 SiO 3 ¯;
8) salts and alkalis:
CuSO 4 + 2CsOH → Cu(OH) 2 ¯ + Cs 2 SO 4.
Acid salts are obtained:
1) when neutralizing polybasic acids with alkali in excess acid:
H 3 PO 4 + NaOH → NaH 2 PO 4 + H 2 O;
2) during the interaction of medium salts with acids:
CaCO 3 + H 2 CO 3 → Ca(HCO 3) 2;
3) during the hydrolysis of salts formed by a weak acid:
Na 2 S + H 2 O → NaHS + NaOH.
The main salts are obtained:
1) during a reaction between a polyvalent metal base and an acid in excess of the base:
Cu(OH) 2 + HCl → CuOHCl + H 2 O;
2) during the interaction of medium salts with alkalis:
СuCl 2 + KOH → CuOHCl + KCl;
3) during the hydrolysis of medium salts formed by weak bases:
AlCl 3 +H 2 O → AlOHCl 2 + HCl.
Salts can interact with acids, alkalis, other salts, and water (hydrolysis reaction):
2H 3 PO 4 + 3Ca(NO 3) 2 → Ca 3 (PO 4) 2 ¯ + 6HNO 3 ;
FeCl 3 + 3NaOH → Fe(OH) 3 ¯ + 3NaCl;
Na 2 S + NiCl 2 → NiS¯ + 2NaCl.
In any case, the ion exchange reaction proceeds to completion only when a poorly soluble, gaseous or weakly dissociating compound is formed.
In addition, salts can interact with metals, provided that the metal is more active (has a more negative electrode potential) than the metal included in the salt:
Fe + CuSO 4 → FeSO 4 + Cu.
Salts are also characterized by decomposition reactions:
BaCO 3 → BaO + CO 2;
2KClO 3 → 2KCl + 3O 2.
OBTAINING AND PROPERTIES
BASES, ACIDS AND SALTS
Experiment 1. Preparation of alkalis.
1.1. Interaction of metal with water.
Pour distilled water into a crystallizer or porcelain cup (about 1/2 of the vessel). Obtain from your teacher a piece of sodium metal, previously dried with filter paper. Drop a piece of sodium into a crystallizer with water. Once the reaction is complete, add a few drops of phenolphthalein. Note the observed phenomena and create an equation for the reaction. Name the resulting compound and write down its structural formula.
1.2. Interaction of metal oxide with water.
Pour distilled water into a test tube (1/3 of the test tube) and place a lump of CaO in it, mix thoroughly, add 1 - 2 drops of phenolphthalein. Note the observed phenomena, write the reaction equation. Name the resulting compound and give its structural formula.