Chemical designation for salt. Classification, preparation and properties of salts. Chemical properties of amphoteric oxides

Salts are electrolytes that dissociate in aqueous solutions to form a metal cation and an acid residue anion.
The classification of salts is given in table. 9.

When writing formulas for any salts, you must be guided by one rule: the total charges of cations and anions must be equal in absolute value. Based on this, indexes should be placed. For example, when writing the formula for aluminum nitrate, we take into account that the charge of the aluminum cation is +3, and the pitrate ion is 1: AlNO 3 (+3), and using indices we equalize the charges (the least common multiple for 3 and 1 is 3. Divide 3 by the absolute value of the charge of the aluminum cation - we get the index. Divide 3 by the absolute value of the charge of the NO 3 anion - we get the index 3). Formula: Al(NO 3) 3

Salt it

Medium, or normal, salts contain only metal cations and anions of the acid residue. Their names are derived from the Latin name of the element forming the acidic residue by adding the appropriate ending depending on the oxidation state of that atom. For example, the sulfuric acid salt Na 2 SO 4 is called (oxidation state of sulfur +6), salt Na 2 S - (oxidation state of sulfur -2), etc. In the table. Table 10 shows the names of salts formed by the most widely used acids.

The names of the middle salts underlie all other groups of salts.

■ 106 Write the formulas of the following average salts: a) calcium sulfate; b) magnesium nitrate; c) aluminum chloride; d) zinc sulfide; d) ; f) potassium carbonate; g) calcium silicate; h) iron (III) phosphate.

Acid salts differ from average salts in that their composition, in addition to the metal cation, includes a hydrogen cation, for example NaHCO3 or Ca(H2PO4)2. An acid salt can be thought of as the product of incomplete replacement of hydrogen atoms in an acid with a metal. Consequently, acid salts can only be formed by two or more basic acids.
The acid salt molecule usually contains an “acidic” ion, the charge of which depends on the stage of dissociation of the acid. For example, the dissociation of phosphoric acid occurs in three steps:

At the first stage of dissociation, a singly charged anion H 2 PO 4 is formed. Consequently, depending on the charge of the metal cation, the formulas of the salts will look like NaH 2 PO 4, Ca(H 2 PO 4) 2, Ba(H 2 PO 4) 2, etc. At the second stage of dissociation, the doubly charged HPO anion is formed 2 4 — . The formulas of the salts will look like this: Na 2 HPO 4, CaHPO 4, etc. The third stage of dissociation does not produce acidic salts.
The names of acidic salts are derived from the names of the middle ones with the addition of the prefix hydro- (from the word “hydrogenium” -):
NaHCO 3 - sodium bicarbonate KHCO 4 - potassium hydrogen sulfate CaHPO 4 - calcium hydrogen phosphate
If the acidic ion contains two hydrogen atoms, for example H 2 PO 4 -, the prefix di- (two) is added to the name of the salt: NaH 2 PO 4 - sodium dihydrogen phosphate, Ca(H 2 PO 4) 2 - calcium dihydrogen phosphate, etc. .d.

■ 107. Write the formulas of the following acid salts: a) calcium hydrogen sulfate; b) magnesium dihydrogen phosphate; c) aluminum hydrogen phosphate; d) barium bicarbonate; e) sodium hydrosulfite; f) magnesium hydrosulfite.
108. Is it possible to obtain acid salts of hydrochloric and nitric acid? Justify your answer.

Basic salts differ from others in that, in addition to the metal cation and the anion of the acid residue, they contain hydroxyl anions, for example Al(OH)(NO3) 2. Here the charge of the aluminum cation is +3, and the charges of the hydroxyl ion-1 and two nitrate ions are 2, for a total of 3.
The names of the main salts are derived from the names of the middle salts with the addition of the word basic, for example: Cu 2 (OH) 2 CO 3 - basic copper carbonate, Al (OH) 2 NO 3 - basic aluminum nitrate.

■ 109. Write the formulas of the following basic salts: a) basic iron (II) chloride; b) basic iron (III) sulfate; c) basic copper (II) nitrate; d) basic calcium chloride; e) basic magnesium chloride; f) basic iron (III) sulfate g) basic aluminum chloride.

Formulas of double salts, for example KAl(SO4)3, are built based on the total charges of both metal cations and the total charge of the anion

The total charge of cations is + 4, the total charge of anions is -4.
The names of double salts are formed in the same way as the middle ones, only the names of both metals are indicated: KAl(SO4)2 - potassium-aluminum sulfate.

■ 110. Write the formulas of the following salts:
a) magnesium phosphate; b) magnesium hydrogen phosphate; c) lead sulfate; d) barium hydrogen sulfate; e) barium hydrosulfite; f) potassium silicate; g) aluminum nitrate; h) copper (II) chloride; i) iron (III) carbonate; j) calcium nitrate; l) potassium carbonate.

Chemical properties of salts

1. All medium salts are strong electrolytes and easily dissociate:
Na 2 SO 4 ⇄ 2Na + + SO 2 4 —
Medium salts can interact with metals that are a number of voltages to the left of the metal that is part of the salt:
Fe + CuSO 4 = Cu + FeSO 4
Fe + Сu 2+ + SO 2 4 — = Сu + Fe 2+ + SO 2 4 —
Fe + Cu 2+ = Cu + Fe 2+
2. Salts react with alkalis and acids according to the rules described in the sections “Bases” and “Acids”:
FeCl 3 + 3NaOH = Fe(OH) 3 ↓ + 3NaCl
Fe 3+ + 3Cl - + 3Na + + 3OH - = Fe(OH) 3 + 3Na + + 3Cl -
Fe 3+ + 3OH - =Fe(OH) 3
Na 2 SO 3 + 2HCl = 2NaCl + H 2 SO 3
2Na + + SO 2 3 - + 2H + + 2Cl - = 2Na + + 2Cl - + SO 2 + H 2 O
2H + + SO 2 3 - = SO 2 + H 2 O
3. Salts can interact with each other, resulting in the formation of new salts:
AgNO 3 + NaCl = NaNO 3 + AgCl
Ag + + NO 3 - + Na + + Cl - = Na + + NO 3 - + AgCl
Ag + + Cl - = AgCl
Since these exchange reactions are carried out mainly in aqueous solutions, they occur only when one of the resulting salts precipitates.
All exchange reactions proceed in accordance with the conditions for the reactions to proceed to completion, listed in § 23, p. 89.

■ 111. Write down equations for the following reactions and, using the solubility table, determine whether they will proceed to completion:
a) barium chloride + ;
b) aluminum chloride + ;
c) sodium phosphate + calcium nitrate;
d) magnesium chloride + potassium sulfate;
e) + lead nitrate;
f) potassium carbonate + manganese sulfate;
g) + potassium sulfate.
Write the equations in molecular and ionic forms.

■ 112. Which of the following substances will iron (II) chloride react with: a) ; b) calcium carbonate; c) sodium hydroxide; d) silicon anhydride; d) ; f) copper (II) hydroxide; and) ?

113. Describe the properties of calcium carbonate as an average salt. Write all equations in molecular and ionic forms.
114. How to carry out a series of transformations:

Write all equations in molecular and ionic forms.
115. What amount of salt will be obtained from the reaction of 8 g of sulfur and 18 g of zinc?
116. What volume of hydrogen will be released when 7 g of iron reacts with 20 g of sulfuric acid?
117. How many moles of table salt will be obtained from the reaction of 120 g of sodium hydroxide and 120 g of hydrochloric acid?
118. How much potassium nitrate will be obtained from the reaction of 2 moles of potassium hydroxide and 130 g of nitric acid?

Hydrolysis of salts

A specific property of salts is their ability to hydrolyze - to undergo hydrolysis (from the Greek “hydro” - water, “lysis” - decomposition), i.e. decomposition under the influence of water. It is impossible to consider hydrolysis as decomposition in the sense in which we usually understand it, but one thing is certain - it always participates in the hydrolysis reaction.
- very weak electrolyte, dissociates poorly
H 2 O ⇄ H + + OH -
and does not change the color of the indicator. Alkalis and acids change the color of indicators, since when they dissociate in solution, an excess of OH - ions (in the case of alkalis) and H + ions in the case of acids is formed. In salts such as NaCl, K 2 SO 4, which are formed by a strong acid (HCl, H 2 SO 4) and a strong base (NaOH, KOH), indicators do not change color, since in a solution of these
There is practically no hydrolysis of salts.
During the hydrolysis of salts, four cases are possible, depending on whether the salt was formed with a strong or weak acid and base.
1. If we take a salt of a strong base and a weak acid, for example K 2 S, the following will happen. Potassium sulfide dissociates into ions as a strong electrolyte:
K 2 S ⇄ 2K + + S 2-
Along with this, it weakly dissociates:
H 2 O ⇄ H + + OH —
The sulfur anion S2- is an anion of weak hydrosulfide acid, which dissociates poorly. This leads to the fact that the S 2- anion begins to attach hydrogen cations to itself from water, gradually forming slightly dissociating groups:
S 2- + H + + OH - = HS - + OH -
HS - + H + + OH - = H 2 S + OH -
Since the H + cations from the water are bound, and the OH - anions remain, the reaction of the medium becomes alkaline. Thus, during the hydrolysis of salts formed by a strong base and a weak acid, the reaction of the medium is always alkaline.

■ 119.Using ionic equations, explain the process of hydrolysis of sodium carbonate.

2. If you take a salt formed by a weak base and a strong acid, for example Fe(NO 3) 3, then when it dissociates, ions are formed:
Fe(NO 3) 3 ⇄ Fe 3+ + 3NO 3 -
The Fe3+ cation is a cation of a weak base - iron, which dissociates very poorly. This leads to the fact that the Fe 3+ cation begins to attach OH - anions from water, forming slightly dissociating groups:
Fe 3+ + H + + OH - = Fe(OH) 2+ + + H +
and onwards
Fe(OH) 2+ + H + + OH - = Fe(OH) 2 + + H +
Finally, the process can reach its last stage:
Fe(OH) 2 + + H + + OH - = Fe(OH) 3 + H +
Consequently, there will be an excess of hydrogen cations in the solution.
Thus, during the hydrolysis of a salt formed by a weak base and a strong acid, the reaction of the medium is always acidic.

■ 120. Using ionic equations, explain the course of hydrolysis of aluminum chloride.

3. If a salt is formed by a strong base and a strong acid, then neither the cation nor the anion binds water ions and the reaction remains neutral. Hydrolysis practically does not occur.
4. If a salt is formed by a weak base and a weak acid, then the reaction of the medium depends on their degree of dissociation. If the base and acid have almost the same value, then the reaction of the medium will be neutral.

■ 121. It is often seen how during an exchange reaction, instead of the expected salt precipitate, a metal precipitate precipitates, for example, in the reaction between iron (III) chloride FeCl 3 and sodium carbonate Na 2 CO 3, not Fe 2 (CO 3) 3 is formed, but Fe( OH) 3 . Explain this phenomenon.
122. Among the salts listed below, indicate those that undergo hydrolysis in solution: KNO 3, Cr 2 (SO 4) 3, Al 2 (CO 3) 3, CaCl 2, K 2 SiO 3, Al 2 (SO 3) 3.

Features of the properties of acid salts

Acidic salts have slightly different properties. They can enter into reactions with the preservation and destruction of the acidic ion. For example, the reaction of an acid salt with an alkali results in the neutralization of the acid salt and the destruction of the acid ion, for example:
NaHSO4 + KOH = KNaSO4 + H2O
double salt
Na + + HSO 4 - + K + + OH - = K + + Na + + SO 2 4 - + H2O
HSO 4 - + OH - = SO 2 4 - + H2O
The destruction of an acidic ion can be represented as follows:
HSO 4 — ⇄ H + + SO 4 2-
H + + SO 2 4 - + OH - = SO 2 4 - + H2O
The acidic ion is also destroyed when reacting with acids:
Mg(HCO3)2 + 2HCl = MgCl2 + 2H2Co3
Mg 2+ + 2НСО 3 — + 2Н + + 2Сl — = Mg 2+ + 2Сl — + 2Н2O + 2СO2
2HCO 3 - + 2H + = 2H2O + 2CO2
HCO 3 - + H + = H2O + CO2
Neutralization can be carried out with the same alkali that formed the salt:
NaHSO4 + NaOH = Na2SO4 + H2O
Na + + HSO 4 - + Na + + OH - = 2Na + + SO 4 2- + H2O
HSO 4 - + OH - = SO 4 2- + H2O
Reactions with salts occur without destruction of the acidic ion:
Ca(HCO3)2 + Na2CO3 = CaCO3 + 2NaHCO3
Ca 2+ + 2НСО 3 — + 2Na + + СО 2 3 — = CaCO3↓+ 2Na + + 2НСО 3 —
Ca 2+ + CO 2 3 - = CaCO3
■ 123. Write the equations for the following reactions in molecular and ionic forms:
a) potassium hydrosulfide +;
b) sodium hydrogen phosphate + potassium hydroxide;
c) calcium dihydrogen phosphate + sodium carbonate;
d) barium bicarbonate + potassium sulfate;
e) calcium hydrosulfite +.

Obtaining salts

Based on the studied properties of the main classes of inorganic substances, 10 methods for obtaining salts can be derived.
1. Interaction of metal with non-metal:
2Na + Cl2 = 2NaCl
Only salts of oxygen-free acids can be obtained in this way. This is not an ionic reaction.
2. Interaction of metal with acid:
Fe + H2SO4 = FeSO4 + H2
Fe + 2H + + SO 2 4 - =Fe 2+ + SO 2 4 - + H2
Fe + 2H + = Fe 2+ + H2
3. Interaction of metal with salt:
Сu + 2AgNO3 = Cu(NO3)2 + 2Ag↓
Сu + 2Ag + + 2NO 3 - = Cu 2+ 2NO 3 - + 2Ag↓
Сu + 2Ag + = Cu 2+ + 2Ag
4. Interaction of a basic oxide with an acid:
СuО + H2SO4 = CuSO4 + H2O
CuO + 2H + + SO 2 4 - = Cu 2+ + SO 2 4 - + H2O
СuО + 2Н + = Cu 2+ + H2O
5. The interaction of a basic oxide with an acid anhydride:
3CaO + P2O5 = Ca3(PO4)2
The reaction is not ionic in nature.
6. Interaction of an acidic oxide with a base:
CO2 + Ca(OH)2 = CaCO3 + H2O
CO2 + Ca 2+ + 2OH - = CaCO3 + H2O
7, Interaction of acids with bases (neutralization):
HNO3 + KOH = KNO3 + H2O
H + + NO 3 — + K + + OH — = K + + NO 3 — + H2O
H + + OH - = H2O

8. The interaction of a base with a salt:
3NaOH + FeCl3 = Fe(OH)3 + 3NaCl
3Na + + 3OH - + Fe 3+ + 3Cl - = Fe(OH)3↓ + 3Na - + 3Cl -
Fe 3+ + 3OH - = Fe(OH)3↓
9. Interaction of acid with salt:
H2SO4 + Na2CO3 = Na2SO4 + H2O+ CO2
2H + + SO 2 4 — + 2Na + + CO 2 3 — =2Na + + SO 2 4 — + H2O + CO2
2H + + CO 2 3 - = H2O + CO2
10. Interaction of salt with salt:
Ba(NO3)2 + FeSO4 = Fe(NO3)2 + BaSO4
Ba 2+ + 2NO 3 - + Fe 2+ + SO 2 4 - = Fe 2+ + 2NO 3 - + BaSO4↓
Ba 2+ + SO 2 4 - = BaSO4↓

■124. Give all the methods for preparing barium sulfate that you know (write all equations in molecular and ionic forms).
125. Give all possible general methods for obtaining zinc chloride.
126. Mixed 40 g of copper oxide and 200 ml of 2 N. sulfuric acid solution. What amount of copper sulfate is formed?
127. How much calcium carbonate will be obtained by reacting 2.8 liters of CO2 with 200 g of 5% Ca(OH)2 solution?
128. Mixed 300 g of 10% sulfuric acid solution and 500 ml of 1.5 N. sodium carbonate solution. How much carbon dioxide will be released?
129. 80 g of zinc containing 10% impurities are treated with 200 ml of 20% hydrochloric acid. How much zinc chloride is formed as a result of the reaction?

Article on the topic of Salt

There are many foods that we are used to eating daily. These include salt. This product is connected not only with our nutrition, but also with life in general. Our article describes various types of salt. In addition, you can find out its positive and negative qualities, as well as the daily intake.

What is salt? General information about the substance

Salt - which in an aqueous solution breaks down into metal cations and anions of acidic residues. It is considered a natural preservative, a source of essential minerals and a must-have spice in the kitchen. In ancient Rome, salt was used to pay salaries and was used to create amulets. This substance was used as a cure for certain diseases.

The largest amount of salt is found in sea water. It can also be found in the mineral halite. It is mined from sedimentary rocks. This salt is no less in demand than classic salt.

In the food industry, salt is a food product that consists of ground crystals of sodium chloride used in cooking. It dissolves in water, but does not change its color. There are different types of table salt. All of them differ in taste, but nevertheless contain sodium chloride.

Each of us knows the expression that salt is white poison. However, it is believed that without it life would not have arisen on Earth. Not everyone knows that salt is contained in the blood.

In the chemical industry, sodium chloride (table salt) is used to create chlorine and soda. It is also often used in cosmetology.

Positive qualities of salt

Different types of salt have both positive and negative properties. This substance contains a lot of microelements. Salt has a positive effect on the digestive system and increases vitality. A small amount of salt in the diet reduces the number of attacks in asthmatics. This substance contains selenium, a useful substance that is an antioxidant. It has a positive effect on cells and protects them from destruction.

All types of table salt help remove harmful and dangerous substances from the body. This compound is excellent for poisoning, as it blocks the process of absorption of toxic components by the intestinal mucosa. Salt also delays their entry into the blood. This supplement helps the body in the fight against radiation and other dangerous radiation. It kills germs very well.
Many types of salt are used in cosmetology. It is added to creams and scrubs. Thanks to this component, pores open and dead cells exfoliate. The salt procedure can be done both at home and in a beauty salon with a specialist.

All types of table salt were used during World War II. Then a napkin was generously moistened in a solution with its addition and applied to the wounded soldier for several days. Thanks to this, the damaged area became clean and had a healthy pink color. It is known that saline solution can also be used in the treatment of tumors.

Negative properties of salt

Any product has both positive and negative qualities. Absolutely all types of salt are no exception. At a medical symposium in 1979, scientists declared that table salt, which we use every day, is a poisonous substance. In their opinion, it suppresses our health.

It is important to know the norm. An excess of sodium in the body leads to excess fluid retention. The result is bags under the eyes, swelling of the face and legs. Regular consumption of excessively salty foods leads to obesity and increased blood pressure. In this regard, a person quickly gets tired and experiences headaches. Excess salt leads to the formation of stones in the urinary tract.

People themselves are to blame for all the harmful qualities of salt. Attempts to make it snow-white and of better quality ended with the fact that today the product contains a huge amount of Surprisingly, natural sea salt, evaporated in the sun, is similar in composition to inorganic blood compounds. The daily salt intake should not exceed 15 grams. It is important to consider its content in finished products.

Main types of table salt

There are three types of salt:

• stone;
• evaporation;
• sea

They are the most basic. All three varieties differ in the method of extraction and purification.

It is gray in color and large in size. This is crushed halite. Surprisingly, this is the only edible mineral in the world. The substance was formed several million years ago in the territory of ancient seas. This type of salt is mined in mines and caves. Then it is cleaned. Unfortunately, table salt contains a large amount of insoluble substances. Over time, they accumulate in the body.

It is distinguished by its snow-white color and small size. To extract it, a mine with a salty layer is filled with water. After this, the so-called brine rises to the top, which is evaporated and purified under high temperatures. For example, “Extra” salt is a product that is 99% sodium chloride. She is considered the most beautiful, snow-white and small. It does not contain solid impurities, but, unfortunately, it does not contain useful trace elements such as iodine, magnesium and bromine. Chemicals are often added to Extra salt to protect it from absorbing liquid. Because of this, the product is poorly soluble in the blood and accumulates in the body.

It is no secret that sea salt is extracted from the seas, lakes and evaporated under the influence of the sun and wind. Unlike other types, it can be fine, medium and coarse. Sea salt contains essential microelements for the body. It is this that is considered a truly natural and useful component. Sea salt contains iodine, magnesium, bromine, iron, zinc and silicon. This is what nutritionists recommend to choose for people who monitor their health and weight.

Recently, sea salt with unusual ingredients has been in extraordinary demand. Among them is a product with kelp. Dried seaweed is added to this salt. It contains organic iodine compounds. This component remains in the product throughout the entire shelf life, as well as during the preparation of not only cold, but also hot dishes. As additional additives, spices, herbs and even bread are added to sea salt with kelp. Surprisingly, it was from the last component that our ancestors prepared black salt. It was illuminated in the church and used as medicine or as a talisman.

There are different types of salt on store shelves. For each of us, this is a spice that we use daily. However, there are many interesting facts associated with this product that not everyone knows about.

Surprisingly, the names of many dishes are associated with salt. Many years ago, salad was a mixture of pickled vegetables. Thanks to this, its name arose, which we know today.

The name of salami sausage is associated with salt. It is made from salted ham. The marinade is also associated with our everyday product.

Scientists believe that the daily salt intake may vary. They recommend first of all paying attention to the time of year and a person’s lifestyle. In the summer, people sweat and lose a large amount of fluid, and that is why experts allow up to 20 grams of salt during this period. Athletes can also adhere to this norm at any time of the year.

Another interesting fact is related to cooking. Surprisingly, coffee lovers can safely add a pinch of spice to their drink. Thanks to this, it will have a richer aroma. Good housewives know that it is salt that will help beat egg whites to stable peaks. You can’t do without it when preparing yeast dough.

Salt in the human body

The types of salts in the body and their properties remain a mystery to many. They are the ones who participate in which is characterized by the entry of mineral components into the body. Salt enters our body along with food and water. It then enters the bloodstream and is transported to cells throughout the body. The most vital types include salt:

• sodium;
• magnesium;
• potassium;
• calcium.

The salts contained in our body perform a wide variety of functions. They participate in the formation of enzymes, ensure proper blood clotting and normalize the alkaline balance in it. Salts also play an important role in fluid regulation.

Salt in water

The types of salts in water play an important role. It is on them that the rigidity of the liquid important for everyone’s life depends. Soft and hard water differ in their combination of chemical and physical properties, as well as the amount of salts dissolved in it, namely calcium and magnesium.

Fresh water is considered to be water that contains no more than 0.1% salts. This is the lowest figure. Sea water is considered the most salty. The percentage of substance content in it ranges up to 35%. Brackish water is distinguished by the amount of salt, which is more than in fresh water, but less than in sea water. There is also a liquid that does not contain this substance. Water that does not contain salt and other components is called distilled.

Aromatic salts

Mineral salts play an important role in our lives. The species that exist today can surprise everyone. Despite the fact that they are all quite similar in taste, experienced chefs not only distinguish them, but also give preference to the most exotic types.

One of the most popular is the Himalayan. It has a pink color. Its deposits were formed about 250 million years ago. The unique color was formed due to the interaction of salt and magma. This spice is pure and natural. Due to its dense consistency, it is often used in construction.
Another popular aromatic salt is Svan. It was formed due to the combination of spices and herbs that are familiar to us. You can either prepare it yourself or purchase a finished product.

Black Hawaiian salt

Black Hawaiian salt is considered one of the most exotic and expensive. It is a marine species and is produced only on the Hawaiian island of Molokai. It contains activated carbon, turmeric and taro. The salt has a hard structure, a mild taste with nutty notes and an unforgettable aroma. Usually it is used at the end of cooking, and also used to decorate the finished dish.

Korean Roasted Bamboo Salt

We are used to using table salt in the form of small white crystals. However, every year more and more exotic species appear that amaze with their taste and color. Korean roasted bamboo salt is a traditional spice in Southeast Asia. The method of preparing it was invented by monks more than 1000 years ago. The collected salt is dried in the sun and then placed in a bamboo stalk. It is covered with yellow clay and fried over a fire. Thanks to this, all harmful components are removed from the salt.

Persian blue salt

Persian blue salt is considered the rarest. It has a pleasant blue color, which is due to its high mineral content. It is extremely useful and in demand.
Persian blue salt is used in preparing the most exquisite and expensive dishes. Experienced chefs claim that its taste is revealed in stages.

Let's sum it up

Salt is a spice that almost all of us use daily. It can affect the body both positively and negatively. Many types of salt differ significantly from the product we add to our food. They differ not only in color, but also in taste. Exotic types of salt are most in demand among chefs.

Unfortunately, regular consumption of excessively salty foods can affect the general condition of the body. That is why it is important to know its daily intake, which you read in our article.

Chemical equations

Chemical equation is the expression of a reaction using chemical formulas. Chemical equations show which substances enter into a chemical reaction and which substances are formed as a result of this reaction. The equation is compiled on the basis of the law of conservation of mass and shows the quantitative relationships of substances participating in a chemical reaction.

As an example, consider the interaction of potassium hydroxide with phosphoric acid:

H 3 PO 4 + 3 KOH = K 3 PO 4 + 3 H 2 O.

From the equation it is clear that 1 mole of orthophosphoric acid (98 g) reacts with 3 moles of potassium hydroxide (3·56 g). As a result of the reaction, 1 mole of potassium phosphate (212 g) and 3 moles of water (3·18 g) are formed.

98 + 168 = 266 g; 212 + 54 = 266 g we see that the mass of substances that entered into the reaction is equal to the mass of the reaction products. The equation of a chemical reaction allows you to make various calculations related to a given reaction.

Complex substances are divided into four classes: oxides, bases, acids and salts.

Oxides- these are complex substances consisting of two elements, one of which is oxygen, i.e. An oxide is a compound of an element with oxygen.

The name of oxides is derived from the name of the element that is part of the oxide. For example, BaO is barium oxide. If the oxide element has a variable valence, then after the name of the element its valence is indicated in parentheses with a Roman numeral. For example, FeO is iron (I) oxide, Fe2O3 is iron (III) oxide.

All oxides are divided into salt-forming and non-salt-forming.

Salt-forming oxides are oxides that form salts as a result of chemical reactions. These are oxides of metals and non-metals, which, when interacting with water, form the corresponding acids, and when interacting with bases, the corresponding acidic and normal salts. For example, copper oxide (CuO) is a salt-forming oxide, because, for example, when it reacts with hydrochloric acid (HCl), a salt is formed:

CuO + 2HCl → CuCl2 + H2O.

As a result of chemical reactions, other salts can be obtained:

CuO + SO3 → CuSO4.

Non-salt-forming oxides are those oxides that do not form salts. Examples include CO, N2O, NO.

Salt-forming oxides are of 3 types: basic (from the word “base”), acidic and amphoteric.

Basic oxides are metal oxides, which correspond to hydroxides, which belong to the class of bases. Basic oxides include, for example, Na2O, K2O, MgO, CaO, etc.

Chemical properties of basic oxides

1. Water-soluble basic oxides react with water to form bases:

Na2O + H2O → 2NaOH.

2. React with acid oxides, forming the corresponding salts

Na2O + SO3 → Na2SO4.

3. React with acids to form salt and water:

CuO + H2SO4 → CuSO4 + H2O.

4. React with amphoteric oxides:

Li2O + Al2O3 → 2LiAlO2.

5. Basic oxides react with acidic oxides to form salts:

Na2O + SO3 = Na2SO4

If the composition of the oxides contains a non-metal or a metal exhibiting the highest valence (usually from IV to VII) as the second element, then such oxides will be acidic. Acidic oxides (acid anhydrides) are those oxides that correspond to hydroxides belonging to the class of acids. These are, for example, CO2, SO3, P2O5, N2O3, Cl2O5, Mn2O7, etc. Acidic oxides dissolve in water and alkalis, forming salt and water.

Chemical properties of acid oxides

1. React with water to form an acid:

SO3 + H2O → H2SO4.

But not all acidic oxides react directly with water (SiO2, etc.).

2. React with based oxides to form a salt:

CO2 + CaO → CaCO3

3. React with alkalis, forming salt and water:

CO2 + Ba(OH)2 → BaCO3 + H2O.

An amphoteric oxide contains an element that has amphoteric properties. Amphotericity refers to the ability of compounds to exhibit acidic and basic properties depending on conditions. For example, zinc oxide ZnO can be either a base or an acid (Zn(OH)2 and H2ZnO2). Amphotericity is expressed in the fact that, depending on the conditions, amphoteric oxides exhibit either basic or acidic properties, for example, Al2O3, Cr2O3, MnO2; Fe2O3 ZnO. For example, the amphoteric nature of zinc oxide manifests itself when it interacts with both hydrochloric acid and sodium hydroxide:

ZnO + 2HCl = ZnCl 2 + H 2 O

ZnO + 2NaOH = Na 2 ZnO 2 + H 2 O

Since not all amphoteric oxides are soluble in water, it is much more difficult to prove the amphoteric nature of such oxides. For example, aluminum (III) oxide exhibits basic properties in the reaction of its fusion with potassium disulfate, and acidic properties when fused with hydroxides:

Al2O3 + 3K2S2O7 = 3K2SO4 + A12(SO4)3

Al2O3 + 2KOH = 2KAlO2 + H2O

For different amphoteric oxides, the duality of properties can be expressed to varying degrees. For example, zinc oxide dissolves equally easily in both acids and alkalis, and iron (III) oxide - Fe2O3 - has predominantly basic properties.

Chemical properties of amphoteric oxides

1. React with acids, forming salt and water:

ZnO + 2HCl → ZnCl2 + H2O.

2. React with solid alkalis (during fusion), forming as a result of the reaction salt - sodium zincate and water:

ZnO + 2NaOH → Na2 ZnO2 + H2O.

When zinc oxide interacts with an alkali solution (the same NaOH), another reaction occurs:

ZnO + 2 NaOH + H2O => Na2.

Coordination number is a characteristic that determines the number of nearby particles: atoms or ions in a molecule or crystal. Each amphoteric metal has its own coordination number. For Be and Zn it is 4; For and Al it is 4 or 6; For and Cr it is 6 or (very rarely) 4;

Amphoteric oxides are usually insoluble in water and do not react with it.

Methods for producing oxides from simple substances are either a direct reaction of the element with oxygen:

or decomposition of complex substances:

a) oxides

4CrO3 = 2Cr2O3 + 3O2-

b) hydroxides

Ca(OH)2 = CaO + H2O

c) acids

H2CO3 = H2O + CO2-

CaCO3 = CaO +CO2

As well as the interaction of acids - oxidizing agents with metals and non-metals:

Cu + 4HNO3 (conc) = Cu(NO3) 2 + 2NO2 + 2H2O

Oxides can be obtained by direct interaction of oxygen with another element, or indirectly (for example, during the decomposition of salts, bases, acids). Under normal conditions, oxides come in solid, liquid and gaseous states; this type of compound is very common in nature. Oxides are found in the Earth's crust. Rust, sand, water, carbon dioxide are oxides.

Grounds- these are complex substances in the molecules of which metal atoms are connected to one or more hydroxyl groups.

Bases are electrolytes that, when dissociated, form only hydroxide ions as anions.

NaOH = Na + + OH -

Ca(OH)2 = CaOH + + OH - = Ca 2 + + 2OH -

There are several signs of classification of bases:

Depending on their solubility in water, bases are divided into alkalis and insoluble. Alkalis are hydroxides of alkali metals (Li, Na, K, Rb, Cs) and alkaline earth metals (Ca, Sr, Ba). All other bases are insoluble.

Depending on the degree of dissociation, bases are divided into strong electrolytes (all alkalis) and weak electrolytes (insoluble bases).

Depending on the number of hydroxyl groups in the molecule, bases are divided into monoacid (1 OH group), for example, sodium hydroxide, potassium hydroxide, diacid (2 OH groups), for example, calcium hydroxide, copper hydroxide (2), and polyacid.

Chemical properties.

OH - ions in solution determine the alkaline environment.

Alkali solutions change the color of indicators:

Phenolphthalein: colorless ® crimson,

Litmus: violet ® blue,

Methyl orange: orange ® yellow.

Alkali solutions react with acidic oxides to form salts of those acids that correspond to the reacting acidic oxides. Depending on the amount of alkali, medium or acidic salts are formed. For example, when calcium hydroxide reacts with carbon(IV) monoxide, calcium carbonate and water are formed:

Ca(OH)2 + CO2 = CaCO3? +H2O

And when calcium hydroxide reacts with excess carbon monoxide (IV), calcium bicarbonate is formed:

Ca(OH)2 + CO2 = Ca(HCO3)2

Ca2+ + 2OH- + CO2 = Ca2+ + 2HCO32-

All bases react with acids to form salt and water, for example: when sodium hydroxide reacts with hydrochloric acid, sodium chloride and water are formed:

NaOH + HCl = NaCl + H2O

Na+ + OH- + H+ + Cl- = Na+ + Cl- + H2O

Copper(II) hydroxide dissolves in hydrochloric acid to form copper(II) chloride and water:

Cu(OH)2 + 2HCl = CuCl2 + 2H2O

Cu(OH)2 + 2H+ + 2Cl- = Cu2+ + 2Cl- + 2H2O

Cu(OH)2 + 2H+ = Cu2+ + 2H2O.

The reaction between an acid and a base is called a neutralization reaction.

When heated, insoluble bases decompose into water and the metal oxide corresponding to the base, for example:

Cu(OH)2 = CuO + H2 2Fe(OH)3 = Fe2O3 + 3H2O

Alkalis interact with salt solutions if one of the conditions for the ion exchange reaction to proceed to completion is met (a precipitate forms),

2NaOH + CuSO4 = Cu(OH)2? + Na2SO4

2OH- + Cu2+ = Cu(OH)2

The reaction occurs due to the binding of copper cations with hydroxide ions.

When barium hydroxide reacts with a solution of sodium sulfate, a precipitate of barium sulfate is formed.

Ba(OH)2 + Na2SO4 = BaSO4? + 2NaOH

Ba2+ + SO42- = BaSO4

The reaction occurs due to the binding of barium cations and sulfate anions.

Acids - These 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 (H2SO4 sulfuric acid, H2SO3 sulfurous acid, HNO3 nitric acid, H3PO4 phosphoric acid, H2CO3 carbonic acid, H2SiO3 silicic acid) and oxygen-free (HF hydrofluoric acid, HCl hydrochloric acid (hydrochloric acid) , HBr hydrobromic acid, HI hydroiodic acid, H2S 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).

ACIDS

The part of an acid molecule without hydrogen is called an acid residue.

Acid residues can consist of one atom (-Cl, -Br, -I) - these are simple acid residues, or they can consist of a group of atoms (-SO3, -PO4, -SiO3) - these are complex residues.

In aqueous solutions, during exchange and substitution reactions, acidic residues are not destroyed:

H2SO4 + CuCl2 → CuSO4 + 2 HCl

The word anhydride means anhydrous, that is, an acid without water. For example,

H2SO4 - H2O → SO3. Anoxic acids do not have anhydrides.

The acid gets its name from the name of the acid-forming element (acid-forming agent) with the addition of the endings “naya” and less often “vaya”: H2SO4 - sulfuric; H2SO3 - coal; H2SiO3 - 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”: HNO3 - nitric, HNO2 - nitrous.

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:

H2 + Cl2 → 2 HCl;

Solutions of the resulting gaseous substances HCl and H2S are acids.

Under normal conditions, acids exist in both liquid and solid states.

Chemical properties of acids

1. 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.

2. React with bases to form water and a salt, which contains an unchanged acidic residue (neutralization reaction):

H2SO4 + Ca(OH)2 → CaSO4 + 2 H2O.

3. React with base oxides to form water and salt. The salt contains the acid residue of the acid that was used in the neutralization reaction:

H3PO4 + Fe2O3 → 2 FePO4 + 3 H2O.

4. 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;

K, Ca, Na, Mn, Al, Zn, Fe, Ni, Sn, Pb, H2, Cu, Hg, Ag, Au.

But the reaction between a solution of hydrochloric acid and copper is impossible, since copper is in the voltage series after hydrogen.

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 → ZnCl2 + H2;

Cu + 4HNO3 → CuNO3 + 2 NO2 + 2 H2O.

However, no matter how different the acids are, they all form hydrogen cations upon dissociation, which determine a number of common properties: sour taste, change in the color of indicators (litmus and methyl orange), interaction with other substances.

The same reaction occurs between metal oxides and most acids

CuO+ H2SO4 = CuSO4+ H2O

Let's describe the reactions:

2) The second reaction should produce a soluble salt. In many cases, the interaction of the metal with the acid practically does not occur because the resulting salt is insoluble and covers the surface of the metal with a protective film, for example:

Рb + H2SO4 =/ PbSO4 + H2

Insoluble lead(II) sulfate stops the acid from reaching the metal, and the reaction stops just before it begins. For this reason, most heavy metals practically do not interact with phosphoric, carbonic and hydrosulfide acids.

3) The third reaction is characteristic of acid solutions, therefore, insoluble acids, such as silicic acid, do not react with metals. A concentrated solution of sulfuric acid and a solution of nitric acid of any concentration interact with metals somewhat differently, therefore the reaction equations between metals and these acids are written in a different way. A dilute solution of sulfuric acid reacts with metals. standing in the voltage series to hydrogen, forming salt and hydrogen.

4) The fourth reaction is a typical ion exchange reaction and occurs only if a precipitate or gas is formed.

Salts - these are complex substances whose molecules consist of metal atoms and acidic residues (sometimes they may contain hydrogen). For example, NaCl is sodium chloride, CaSO4 is calcium sulfate, etc.

Almost all salts are ionic compounds, therefore, ions of acidic residues and metal ions are bound together in salts:

Na+Cl - sodium chloride

Ca2+SO42 - calcium sulfate, etc.

A salt is the product of partial or complete substitution of a metal for the hydrogen atoms of an acid.

Hence, the following types of salts are distinguished:

1. Medium salts - all hydrogen atoms in the acid are replaced by a metal: Na2CO3, KNO3, etc.

2. Acidic salts - not all hydrogen atoms in the acid are replaced by a metal. Of course, acid salts can only form di- or polybasic acids. Monobasic acids cannot produce acid salts: NaHCO3, NaH2PO4, etc. d.

3. Double salts - the hydrogen atoms of a di- or polybasic acid are replaced not by one metal, but by two different ones: NaKCO3, KAl(SO4)2, etc.

4. Basic salts can be considered as products of incomplete, or partial, substitution of hydroxyl groups of bases with acidic residues: Al(OH)SO4, Zn(OH)Cl, etc.

According to international nomenclature, the name of the salt of each acid comes from the Latin name of the element. For example, salts of sulfuric acid are called sulfates: CaSO4 - calcium sulfate, MgSO4 - magnesium sulfate, etc.; salts of hydrochloric acid are called chlorides: NaCl - sodium chloride, ZnCI2 - zinc chloride, etc.

The particle “bi” or “hydro” is added to the name of salts of dibasic acids: Mg(HCl3)2 - magnesium bicarbonate or bicarbonate.

Provided that in a tribasic acid only one hydrogen atom is replaced by a metal, then the prefix “dihydro” is added: NaH2PO4 - sodium dihydrogen phosphate.

Salts are solid substances with very different solubility in water.

The chemical properties of salts are determined by the properties of the cations and anions that are part of them.

1. Some salts decompose when heated:

CaCO3 = CaO + CO2

2. React with acids to form a new salt and a new acid. To carry out this reaction, the acid must be stronger than the salt affected by the acid:

2NaCl + H2SO4 → Na2SO4 + 2HCl.

3. Interact with bases, forming a new salt and a new base:

Ba(OH)2 + MgSO4 → BaSO4↓ + Mg(OH)2.

4. Interact with each other to form new salts:

NaCl + AgNO3 → AgCl + NaNO3.

5. They interact with metals that are in the same range of activity as the metal that is part of the salt.

Salts are complex substances that are the product of complete or incomplete replacement of hydrogen atoms of an acid with metal atoms, or replacement of hydroxyl groups of a base with an acidic residue.

Depending on the composition, salts are divided into medium (Na2SO4, K3PO4), acidic (NaHCO3, MgHPO4), basic (FeOHCl2, Al(OH)2Cl, (CaOH)2CO3, double (KAl(SO4)2), complex (Ag[( NH3)2]Cl, K4).

Medium salts

Medium salts are salts that are the product of complete replacement of the hydrogen atoms of the corresponding acid with metal atoms or the NH4+ ion. For example:

H2CO3 ® (NH4)2CO3; H3PO4 ® Na3PO4

The name of the average salt is formed from the name of the anion followed by the name of the cation. For salts of oxygen-free acids, the name of the salt is made up of the Latin name of the non-metal with the addition of the suffix –id, for example, NaCl - sodium chloride. If a non-metal exhibits a variable degree of oxidation, then after its name the oxidation state of the metal is indicated in parentheses in Roman numerals: FeS - iron (II) sulfide, Fe2S3 - iron (III) sulfide.

For salts of oxygen-containing acids, the ending is added to the Latin root of the element name –at for higher oxidation states, -it for lower ones. For example,

K2SiO3 – potassium silicate, KNO2 – potassium nitrite,

KNO3 – potassium nitrate, K3PO4 – potassium phosphate,

Fe2(SO4)3 – iron (III) sulfate, Na2SO3 – sodium sulfite.

For salts of some acids the prefix is ​​used –hypo for lower oxidation states and –trans for high oxidation states. For example,

KClO – potassium hypochlorite, KClO2 – potassium chlorite,

KClO3 – potassium chlorate, KClO4 – potassium perchlorate.

Methods for obtaining medium salts:

Interaction of metals with non-metals, acids and salts:

2Na + Cl2 = 2NaCl

Zn + 2HCl = ZnCl2 + H2

Fe + CuSO4 = FeSO4 + Cu

Interaction of oxides:

basic with acids BaO + 2HNO3 = Ba(NO3)2 + H2O

acidic with alkali 2NaOH + SiO2 = Na2SiO3 + H2O

basic oxides with acidic Na2O + CO2 = Na2CO3

The interaction of acids with bases and with amphoteric hydroxides:

KOH + HCl = KCl + H2O

Cr(OH)3 + 3HNO3 = Cr(NO3)3 + 3H2O

The interaction of salts with acids, with alkalis and salts:

Na2CO3 + 2HCl = 2NaCl + CO2 + H2O

FeCl3 + 3KOH = 3KCl + Fe(OH)3¯

Na2SO4 + BaCl2 = BaSO4¯ + 2NaCl

Chemical properties of medium salts:

Interaction with metals

Zn + Hg(NO3)2 = Zn(NO3)2 + Hg

Interaction with acids

AgNO3 + HCl = AgCl¯ + HNO3

Interaction with alkalis

CuSO4 + 2NaOH = Cu(OH)2¯ + Na2SO4

Interaction with salts

CaCl2 + Na2CO3 = CaCO3¯ + 2NaCl

Decomposition of salts

NH4Cl = NH3 + HCl

CaCO3 = CaO + CO2

(NH4)2Cr2O7 = N2 + Cr2O3 + 4H2O

Acid salts

Acid salts are products of incomplete replacement of hydrogen atoms in molecules of polybasic acids with metal atoms.

For example: H2CO3 ® NaHCO3

H3PO4 ® NaH2PO4 ® Na2HPO4

When naming an acidic salt, the prefix is ​​added to the name of the corresponding average salt hydro-, which indicates the presence of hydrogen atoms in the acid residue.

For example, NaHS is sodium hydrogen sulfide, Na2HPO4 is sodium hydrogen phosphate, NaH2PO4 is sodium dihydrogen phosphate.

Acid salts can be obtained:

The action of excess polybasic acids on basic oxides, alkalis and medium salts:

K2O + 2H2S = 2KHS + H2O

NaOH + H2SO4 = NaHSO4 + H2O

K2SO4 + H2SO4 = 2KHSO4

The action of excess acid oxides on alkalis

NaOH + CO2 = NaHCO3

Chemical properties of acid salts:

Interaction with excess alkali

Ca(HCO3)2 + Ca(OH)2 = 2CaCO3 + 2H2O

Interaction with acids

Ca(HCO3)2 + 2HCl = CaCl2 + 2H2O + 2CO2

Decomposition

Ca(HCO3)2 = CaCO3 + CO2 + H2O

Basic salts

Basic salts are products of incomplete replacement of the hydroxo group in the molecules of polyacid bases with acidic residues.

Mg(OH)2 ® MgOHNO3

Fe(OH)3 ®Fe(OH)2Cl ® FeOHCl2

When naming the main salt, the prefix is ​​added to the name of the corresponding middle salt hydroxo-, which indicates the presence of a hydroxo group. For example, CrOHCl2 is chromium (III) hydroxychloride, Cr(OH)2Cl is chromium (III) dihydroxychloride.

Basic salts can be obtained:

Incomplete neutralization of bases by acids

Salts can also be considered as the products of complete or partial replacement of hydrogen ions in acid molecules with metal ions (or complex positive ions, for example, ammonium ion NH) or as the product of complete or partial replacement of hydroxyl groups in basic hydroxide molecules with acidic residues. With complete substitution we get medium (normal) salts. With incomplete replacement of H + ions in acid molecules, the result is acid salts, with incomplete substitution of OH - groups in base molecules – basic salts. Examples of salt formation:

H3PO4 + 3NaOH
Na 3 PO 4 + 3H 2 O

Na 3 PO 4 ( phosphate sodium) – medium (normal salt);

H3PO4 + NaOH
NaH 2 PO 4 + H 2 O

NaH 2 PO 4 (dihydrogen phosphate sodium) – acidic salt;

Mq(OH) 2 + HCl
MqOHCl + H2O

MqOHCl ( hydroxychloride magnesium) is the main salt.

Salts formed by two metals and one acid are called double salts. For example, potassium aluminum sulfate (potassium alum) KAl(SO 4) 2 *12H 2 O.

Salts formed by one metal and two acids are called mixed salts. For example, calcium chloride-hypochloride CaCl(ClO) or CaOCl 2 is a calcium salt of hydrochloric HCl and hypochlorous acids HClO.

Double and mixed salts, when dissolved in water, dissociate into all the ions that make up their molecules.

For example, KAl(SO 4) 2
K + + Al 3+ + 2SO ;

CaCl(ClO)
Ca 2+ + Cl - + ClO - .

Complex salts- these are complex substances in which it is possible to isolate central atom(complexing agent) and associated molecules and ions - ligands. The central atom and ligands form complex (inner sphere), which when writing the formula of a complex compound is enclosed in square brackets. The number of ligands in the inner sphere is called coordination number. The molecules and ions surrounding the complex form outer sphere.

Central atom Ligand

K 3

Coordination number

The name of the salts is formed from the name of the anion followed by the name of the cation.

For salts of oxygen-free acids, the suffix is ​​added to the name of the non-metal - id, for example, NaCl sodium chloride, FeS iron (II) sulfide.

When naming salts of oxygen-containing acids, the ending is added to the Latin root of the element name -at for higher oxidation states, -it for lower ones (for some acids the prefix is ​​used hypo- for low oxidation states of non-metal; for salts of perchloric and permanganic acids the prefix is ​​used per-). For example, CaCO 3 - calcium carbonate, Fe 2 (SO 4) 3 - iron (III) sulfate, FeSO 3 - iron (II) sulfite, KOSl - potassium hypochlorite, KClO 2 - potassium chlorite, KClO 3 - potassium chlorate, KClO 4 – potassium perchlorate, KMnO 4 - potassium permanganate, K 2 Cr 2 O 7 – potassium dichromate.

The names of complex ions include the ligands first. The name of the complex ion is completed by the name of the metal, indicating the corresponding oxidation state (in Roman numerals in parentheses). The names of complex cations use Russian names of metals, for example, [ Cu(NH 3) 4 ]Cl 2 - tetraammine copper (II) chloride. The names of complex anions use the Latin names of metals with the suffix –at, for example, K – potassium tetrahydroxoaluminate.

Chemical properties of salts

See properties of bases.

See properties of acids.

SiO 2 + CaCO 3
CaSiO 3 + CO 2 .

Amphoteric oxides (they are all non-volatile) displace volatile oxides from their salts during fusion

Al 2 O 3 + K 2 CO 3
2KAlO 2 + CO 2 .

5. Salt 1 + salt 2
salt 3 + salt 4.

An exchange reaction between salts occurs in solution (both salts must be soluble) only if at least one of the products is a precipitate

AqNO3 + NaCl
AqCl + NaNO3.

6. Salt of a less active metal + More active metal
Less active metal + salt.

Exceptions - alkali and alkaline earth metals in solution primarily react with water

Fe + CuCl 2
FeCl 2 +Cu.

7. Salt
thermal decomposition products.

I) Salts of nitric acid. The products of thermal decomposition of nitrates depend on the position of the metal in the series of metal stresses:

a) if the metal is to the left of Mq (excluding Li): MeNO 3
MeNO 2 + O 2 ;

b) if the metal is from Mq to Cu, as well as Li: MeNO 3
MeO + NO 2 + O 2;

c) if the metal is to the right of Cu: MeNO 3
Me + NO 2 + O 2.

II) Salts of carbonic acid. Almost all carbonates decompose to the corresponding metal and CO 2. Carbonates of alkali and alkaline earth metals except Li do not decompose when heated. Silver and mercury carbonates decompose to free metal

MeSO 3
MeO + CO 2;

2Aq 2 CO 3
4Aq + 2CO 2 + O 2 .

All hydrocarbonates decompose to the corresponding carbonate.

Me(HCO 3) 2
MeCO 3 + CO 2 +H 2 O.

III) Ammonium salts. Many ammonium salts decompose when heated, releasing NH 3 and the corresponding acid or its decomposition products. Some ammonium salts containing oxidizing anions decompose to release N2, NO, NO2

NH4Cl
NH 3 +HCl ;

NH4NO2
N 2 +2H 2 O;

(NH 4) 2 Cr 2 O 7
N 2 + Cr 2 O 7 + 4H 2 O.

In table 1 shows the names of acids and their average salts.

Names of the most important acids and their middle salts

End of table. 1

EXAMPLES OF SOLVING PROBLEMS

Task 1. Write the formulas of the following compounds: calcium carbonate, calcium carbide, magnesium hydrogen phosphate, sodium hydrosulfide, iron (III) nitrate, lithium nitride, copper (II) hydroxycarbonate, ammonium dichromate, barium bromide, potassium hexacyanoferrate (II), sodium tetrahydroxoaluminate.

Solution. Calcium carbonate – CaCO 3, calcium carbide – CaC 2, magnesium hydrogen phosphate – MqHPO 4, sodium hydrosulfide – NaHS, iron (III) nitrate – Fe(NO 3) 3, lithium nitride – Li 3 N, copper (II) hydroxycarbonate – 2 CO 3, ammonium dichromate - (NH 4) 2 Cr 2 O 7, barium bromide - BaBr 2, potassium hexacyanoferrate (II) - K 4, sodium tetrahydroxoaluminate - Na.

Task 2. Give examples of the formation of salt: a) from two simple substances; b) from two complex substances; c) from simple and complex substances.

Solution.

a) iron, when heated with sulfur, forms iron (II) sulfide:

Fe+S
FeS;

b) salts enter into exchange reactions with each other in an aqueous solution if one of the products precipitates:

AqNO3 + NaCl
AqCl +NaNO 3 ;

c) salts are formed when metals are dissolved in acids:

Zn + H2SO4
ZnSO 4 +H 2 .

Task 3. During the decomposition of magnesium carbonate, carbon monoxide (IV) was released, which was passed through lime water (taken in excess). In this case, a precipitate weighing 2.5 g was formed. Calculate the mass of magnesium carbonate taken for the reaction.

Solution.

We compose the equations of the corresponding reactions:

MqCO3
MqO +CO 2 ;

CO 2 + Ca(OH) 2
CaCO 3 +H 2 O.

2. Calculate the molar masses of calcium carbonate and magnesium carbonate using the periodic table of chemical elements:

M(CaCO 3) = 40+12+16*3 = 100g/mol;

M(MqCO 3) = 24+12+16*3 = 84 g/mol.

3. Calculate the amount of calcium carbonate substance (precipitated substance):

n(CaCO 3)=
.

From the reaction equations it follows that

n(MqCO 3)=n(CaCO 3)=0.025 mol.

We calculate the mass of calcium carbonate taken for the reaction:

m(MqCO 3)=n(MqCO 3)*M(MqCO 3)= 0.025mol*84g/mol=2.1g.

Answer: m(MqCO 3) = 2.1 g.

Task 4. Write the reaction equations that allow the following transformations to occur:

Mq
MQSO 4
Mq(NO 3) 2
MqO
(CH 3 COO) 2 Mq.

Solution.

Magnesium dissolves in dilute sulfuric acid:

Mq + H 2 SO 4
MqSO 4 +H 2 .

Magnesium sulfate enters into an exchange reaction in an aqueous solution with barium nitrate:

MqSO 4 + Ba(NO 3) 2
BaSO 4 +Mq(NO 3) 2.

When strongly heated, magnesium nitrate decomposes:

2Mq(NO 3) 2
2MqO+ 4NO 2 + O 2 .

4. Magnesium oxide is the main oxide. It dissolves in acetic acid

MqO + 2CH 3 COOH
(CH 3 COO) 2 Mq + H 2 O.

Glinka, N.L. General chemistry. / N.L. Glinka. – M.: Integral-press, 2002.

Glinka, N.L. Problems and exercises in general chemistry.

/ N.L. Glinka. - M.: Integral-press, 2003.

Gabrielyan, O.S. Chemistry. 11th grade: educational. for general education

institutions. / O.S. Gabrielyan, G.G. Lysova.