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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, using specific examples, of how salts should be called correctly.
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 a hydrochloric acid residue (Cl). Name of salt: iron (III) chloride. Please note: 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 valence 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 that you refer to the relevant sections of the chemistry reference book: "
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.
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.
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):
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. Inorganic acids include: sulfuric, nitric, boric, 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.
Let's consider the basic chemical properties of acids.
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 chemical reactions of acid with metals occur, 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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Acids- complex substances consisting of one or more hydrogen atoms that can be replaced by metal atoms and acidic residues.
Classification of acids
1. By the number of hydrogen atoms: number of hydrogen atoms ( n ) determines the basicity of acids:
n= 1 monobase
n= 2 dibase
n= 3 tribase
2. By composition:
a) Table of oxygen-containing acids, acid residues and corresponding acid oxides:
Acid (H n A) |
Acid residue (A) |
Corresponding acid oxide |
H 2 SO 4 sulfuric |
SO 4 (II) sulfate |
SO3 sulfur oxide (VI) |
HNO 3 nitrogen |
NO3(I)nitrate |
N 2 O 5 nitric oxide (V) |
HMnO 4 manganese |
MnO 4 (I) permanganate |
Mn2O7 manganese oxide ( VII) |
H 2 SO 3 sulfurous |
SO 3 (II) sulfite |
SO2 sulfur oxide (IV) |
H 3 PO 4 orthophosphoric |
PO 4 (III) orthophosphate |
P 2 O 5 phosphorus oxide (V) |
HNO 2 nitrogenous |
NO 2 (I) nitrite |
N 2 O 3 nitric oxide (III) |
H 2 CO 3 coal |
CO 3 (II) carbonate |
CO2 carbon monoxide ( IV) |
H 2 SiO 3 silicon |
SiO 3 (II) silicate |
SiO 2 silicon(IV) oxide |
HClO hypochlorous |
ClO(I) hypochlorite |
C l 2 O chlorine oxide (I) |
HClO 2 chloride |
ClO 2 (I) chlorite |
C l 2 O 3 chlorine oxide (III) |
HClO 3 chlorate |
ClO 3 (I) chlorate |
C l 2 O 5 chlorine oxide (V) |
HClO 4 chlorine |
ClO 4 (I) perchlorate |
C l 2 O 7 chlorine oxide (VII) |
b) Table of oxygen-free acids
Acid (H n A) |
Acid residue (A) |
HCl hydrochloric, hydrochloric |
Cl(I) chloride |
H 2 S hydrogen sulfide |
S(II) sulfide |
HBr hydrogen bromide |
Br(I) bromide |
HI hydrogen iodide |
I(I)iodide |
HF hydrogen fluoride, fluoride |
F(I) fluoride |
Physical properties of acids
Many acids, such as sulfuric, nitric, and hydrochloric, are colorless liquids. solid acids are also known: orthophosphoric, metaphosphoric
HPO 3, boric H 3 BO 3 . Almost all acids are soluble in water. An example of an insoluble acid is silicic acid H2SiO3 . Acid solutions have a sour taste. For example, many fruits are given a sour taste by the acids they contain. Hence the names of acids: citric, malic, etc.Methods for producing acids
oxygen-free |
oxygen-containing |
HCl, HBr, HI, HF, H2S |
HNO 3, H 2 SO 4 and others |
RECEIVING |
|
1. Direct interaction of nonmetals H 2 + Cl 2 = 2 HCl |
1. Acidic oxide + water = acid SO 3 + H 2 O = H 2 SO 4 |
2. Exchange reaction between salt and less volatile acid 2 NaCl (tv.) + H 2 SO 4 (conc.) = Na 2 SO 4 + 2HCl |
Chemical properties of acids
1. Change the color of the indicators
Indicator name |
Neutral environment |
Acidic environment |
Litmus |
Violet |
Red |
Phenolphthalein |
Colorless |
Colorless |
Methyl orange |
Orange |
Red |
Universal indicator paper |
Orange |
Red |
2. React with metals in the activity series up to H 2
(excl. HNO 3 -Nitric acid)
Video "Interaction of acids with metals"
Me + ACID = SALT + H 2 (r. substitution)
Zn + 2 HCl = ZnCl 2 + H 2
3. With basic (amphoteric) oxides – metal oxides
Video "Interaction of metal oxides with acids"
Fur x O y + ACID = SALT + H 2 O (exchange ruble)
4. React with bases – neutralization reaction
ACID + BASE= SALT+ H 2 O (exchange ruble)
H 3 PO 4 + 3 NaOH = Na 3 PO 4 + 3 H 2 O
5. React with salts of weak, volatile acids - if acid forms, precipitates or gas evolves:
2 NaCl (tv.) + H 2 SO 4 (conc.) = Na 2 SO 4 + 2HCl ( R . exchange )
Video "Interaction of acids with salts"
6. Decomposition of oxygen-containing acids when heated
(excl. H 2 SO 4 ; H 3 P.O. 4 )
ACID = ACID OXIDE + WATER (r. expansion)
Remember!Unstable acids (carbonic and sulfurous acids) - decompose into gas and water:
H 2 CO 3 ↔ H 2 O + CO 2
H 2 SO 3 ↔ H 2 O + SO 2
Hydrogen sulfide acid in products released as gas:
CaS + 2HCl = H 2 S+CaCl2
ASSIGNMENT TASKS
No. 1. Distribute the chemical formulas of acids in a table. Give them names:
LiOH, Mn 2 O 7, CaO, Na 3 PO 4, H 2 S, MnO, Fe (OH) 3, Cr 2 O 3, HI, HClO 4, HBr, CaCl 2, Na 2 O, HCl, H 2 SO 4, HNO 3, HMnO 4, Ca (OH) 2, SiO 2, Acids
Bes-sour-
native
Oxygen-containing
soluble
insoluble
one-
basic
two-basic
three-basic
No. 2. Write down the reaction equations:
Ca + HCl
Na+H2SO4
Al+H2S
Ca+H3PO4
Name the reaction products.
No. 3. Write down reaction equations and name the products:
Na 2 O + H 2 CO 3
ZnO + HCl
CaO + HNO3
Fe 2 O 3 + H 2 SO 4
No. 4. Write down equations for the reactions of acids with bases and salts:
KOH + HNO3
NaOH + H2SO3
Ca(OH) 2 + H 2 S
Al(OH) 3 + HF
HCl + Na 2 SiO 3
H2SO4 + K2CO3
HNO3 + CaCO3
Name the reaction products.
EXERCISES
Trainer No. 1. "Formula and names of acids"
Trainer No. 2. "Establishing correspondence: acid formula - oxide formula"
Safety precautions - First aid in case of acid contact with skin
Safety precautions -
Acids can be classified based on different criteria:
The basicity of an acid is the number of “mobile” hydrogen atoms in its molecule, capable of being split off from the acid molecule in the form of hydrogen cations H + upon dissociation, and also replaced by metal atoms:
Acids dissociate in aqueous solutions into hydrogen cations and acid residues. As already mentioned, acids are divided into well-dissociating (strong) and low-dissociating (weak). When writing the dissociation equation for strong monobasic acids, either one right-pointing arrow () or an equal sign (=) is used, which shows the virtual irreversibility of such dissociation. For example, the dissociation equation for strong hydrochloric acid can be written in two ways:
or in this form: HCl = H + + Cl -
or in this way: HCl → H + + Cl -
In fact, the direction of the arrow tells us that the reverse process of combining hydrogen cations with acidic residues (association) practically does not occur in strong acids.
If we want to write the dissociation equation of a weak monoprotic acid, we must use two arrows in the equation instead of the sign. This sign reflects the reversibility of the dissociation of weak acids - in their case, the reverse process of combining hydrogen cations with acidic residues is strongly pronounced:
CH 3 COOH CH 3 COO — + H +
Polybasic acids dissociate stepwise, i.e. Hydrogen cations are separated from their molecules not simultaneously, but one by one. For this reason, the dissociation of such acids is expressed not by one, but by several equations, the number of which is equal to the basicity of the acid. For example, the dissociation of tribasic phosphoric acid occurs in three steps with the alternating separation of H + cations:
H 3 PO 4 H + + H 2 PO 4 —
H 2 PO 4 - H + + HPO 4 2-
HPO 4 2- H + + PO 4 3-
It should be noted that each subsequent stage of dissociation occurs to a lesser extent than the previous one. That is, H 3 PO 4 molecules dissociate better (to a greater extent) than H 2 PO 4 - ions, which, in turn, dissociate better than HPO 4 2- ions. This phenomenon is associated with an increase in the charge of acidic residues, as a result of which the strength of the bond between them and positive H + ions increases.
Of the polybasic acids, the exception is sulfuric acid. Since this acid dissociates well in both stages, it is permissible to write the equation of its dissociation in one stage:
H 2 SO 4 2H + + SO 4 2-
The seventh point in the classification of acids is their oxidizing properties. It was stated that acids are weak oxidizing agents and strong oxidizing agents. The vast majority of acids (almost all except H 2 SO 4 (conc.) and HNO 3) are weak oxidizing agents, since they can only exhibit their oxidizing ability due to hydrogen cations. Such acids can oxidize only those metals that are in the activity series to the left of hydrogen, and the products form a salt of the corresponding metal and hydrogen. For example:
H 2 SO 4 (diluted) + Zn ZnSO 4 + H 2
2HCl + Fe FeCl 2 + H 2
As for strong oxidizing acids, i.e. H 2 SO 4 (conc.) and HNO 3, then the list of metals on which they act is much wider, and it includes all metals before hydrogen in the activity series, and almost everything after. That is, concentrated sulfuric acid and nitric acid of any concentration, for example, will oxidize even low-active metals such as copper, mercury, and silver. The interaction of nitric acid and concentrated sulfuric acid with metals, as well as some other substances, due to their specificity, will be discussed separately at the end of this chapter.
Acids react with basic and amphoteric oxides. Silicic acid, since it is insoluble, does not react with low-active basic oxides and amphoteric oxides:
H 2 SO 4 + ZnO ZnSO 4 + H 2 O
6HNO 3 + Fe 2 O 3 2Fe(NO 3) 3 + 3H 2 O
H 2 SiO 3 + FeO ≠
HCl + NaOH H 2 O + NaCl
3H 2 SO 4 + 2Al(OH) 3 Al 2 (SO 4) 3 + 6H 2 O
This reaction occurs if a precipitate, gas, or a significantly weaker acid is formed than the one that reacts. For example:
H 2 SO 4 + Ba(NO 3) 2 BaSO 4 ↓ + 2HNO 3
CH 3 COOH + Na 2 SO 3 CH 3 COONa + SO 2 + H 2 O
HCOONa + HCl HCOOH + NaCl
As mentioned above, nitric acid in any concentration, as well as sulfuric acid exclusively in a concentrated state, are very strong oxidizing agents. In particular, unlike other acids, they oxidize not only metals that are located before hydrogen in the activity series, but also almost all metals after it (except platinum and gold).
For example, they are capable of oxidizing copper, silver and mercury. However, one should firmly grasp the fact that a number of metals (Fe, Cr, Al), despite the fact that they are quite active (available before hydrogen), nevertheless do not react with concentrated HNO 3 and concentrated H 2 SO 4 without heating due to the phenomenon of passivation - a protective film of solid oxidation products is formed on the surface of such metals, which does not allow molecules of concentrated sulfuric and concentrated nitric acids to penetrate deep into the metal for the reaction to occur. However, with strong heating, the reaction still occurs.
In the case of interaction with metals, the obligatory products are always the salt of the corresponding metal and the acid used, as well as water. A third product is also always isolated, the formula of which depends on many factors, in particular, such as the activity of metals, as well as the concentration of acids and the reaction temperature.
The high oxidizing ability of concentrated sulfuric and concentrated nitric acids allows them to react not only with practically all metals of the activity series, but even with many solid non-metals, in particular with phosphorus, sulfur, and carbon. The table below clearly shows the products of the interaction of sulfuric and nitric acids with metals and non-metals depending on the concentration:
All oxygen-free acids (except HF) can exhibit reducing properties due to the chemical element included in the anion under the action of various oxidizing agents. For example, all hydrohalic acids (except HF) are oxidized by manganese dioxide, potassium permanganate, and potassium dichromate. In this case, halide ions are oxidized to free halogens:
4HCl + MnO 2 MnCl 2 + Cl 2 + 2H 2 O
18HBr + 2KMnO 4 2KBr + 2MnBr 2 + 8H 2 O + 5Br 2
14НI + K 2 Cr 2 O 7 3I 2 ↓ + 2Crl 3 + 2KI + 7H 2 O
Among all hydrohalic acids, hydroiodic acid has the greatest reducing activity. Unlike other hydrohalic acids, even ferric oxide and salts can oxidize it.
6HI + Fe 2 O 3 2FeI 2 + I 2 ↓ + 3H 2 O
2HI + 2FeCl 3 2FeCl 2 + I 2 ↓ + 2HCl
Hydrogen sulfide acid H 2 S also has high reducing activity. Even an oxidizing agent such as sulfur dioxide can oxidize it.