All ammonium salts. Ammonium salts - methods of obtaining, use in the national economy
Nitrogen forms several compounds with hydrogen; of these, ammonia is the most important - a colorless gas with a characteristic pungent odor (the smell of "ammonia").
In the laboratory, ammonia is usually produced by heating ammonium chloride with slaked lime. The reaction is expressed by the equation
The released ammonia contains water vapor. For drying, it is passed through soda lime (a mixture of lime and caustic soda).
Rice. 114. A device for demonstrating the combustion of ammonia in oxygen.
The mass of 1 liter of ammonia under normal conditions is 0.77 g. Since this gas is much lighter than air, it can be collected in vessels turned upside down.
When cooled to ammonia under normal pressure, it turns into a transparent liquid, which solidifies at .
Electronic structure and spatial structure ammonia molecules are discussed in § 43. In liquid ammonia, the molecules are interconnected hydrogen bonds, which causes a relatively high boiling point of ammonia, which does not correspond to its low molecular weight (17).
Ammonia is very soluble in water: 1 volume of water dissolves about 700 volumes of ammonia at room temperature. The concentrated solution contains (wt.) and has a density. A solution of ammonia in water is sometimes called ammonia. Ordinary medical ammonia contains. With increasing temperature, the solubility of ammonia decreases, so it is released when heated from a concentrated solution, which is sometimes used in laboratories to obtain small amounts of gaseous ammonia.
At a low temperature, a crystalline hydrate can be isolated from an ammonia solution, melting at -. The composition crystalline hydrate is also known. In these hydrates, water and ammonia molecules are linked by hydrogen bonds.
Chemically, ammonia is quite active; it interacts with many substances. In ammonia, nitrogen has the lowest oxidation state. Therefore, ammonia has only reducing properties. If a current is passed through a tube inserted into another wide tube (Fig. 114), through which oxygen passes, then ammonia can be easily ignited; it burns with a pale greenish flame. When ammonia burns, water and free nitrogen are formed:
Under other conditions, ammonia can be oxidized to nitric oxide (see § 143).
Unlike hydrogen compounds of non-metals of groups VI and VII, ammonia does not possess acid properties. However, hydrogen atoms in its molecule can be replaced by metal atoms.
When hydrogen is completely replaced by a metal, compounds called nitrides are formed. Some of them, such as calcium and magnesium nitrides, are obtained by direct interaction of nitrogen with metals at high temperature;
When in contact with water, many nitrides are completely hydrolyzed to form ammonia and metal hydroxide. For instance:
When only one hydrogen atom is replaced by metals in ammonia molecules, metal amides are formed. So, by passing ammonia over molten sodium, sodium amide can be obtained in the form of colorless crystals:
Water decomposes sodium amide;
Possessing strong basic and water-removing properties, sodium amide has found application in some organic synthesis, for example, in the production of indigo dye and some drugs.
Hydrogen in ammonia can also be replaced by halogens. So, under the action of chlorine on a concentrated solution of ammonium chloride, chlorine nitride, or nitrogen chloride, is obtained,
in the form of a heavy oily explosive liquid.
Similar properties have iodine nitride (nitrogen iodide), which is formed in the form of a black, water-insoluble powder by the action of iodine on ammonia. When wet, it is safe, but when dried, it explodes at the slightest touch; in this case, violet iodine vapors are released.
With fluorine, nitrogen forms stable nitrogen fluoride.
From the data in Table. 6 (p. 118) it can be seen that the electronegativity of chlorine and water is less, and that of fluorine is greater than the electronegativity of nitrogen. It follows that in compounds and the degree of oxidation of nitrogen is -3, and in it is equal to. Therefore, nitrogen fluoride differs in properties from the nitrides of chlorine and iodine. For example, when interacting with water, either ammonia is formed, and in the case nitric oxide (III) is obtained;
The nitrogen atom in the ammonia molecule is bound by three covalent bonds with hydrogen atoms and retains one unshared electron pair:
Acting as an electron pair donor, the nitrogen atom can participate in the formation of a fourth covalent bond with other atoms or ions with electron-withdrawing properties by the donor-acceptor method.
This explains the extremely characteristic ability of ammonia to enter into addition reactions.
Examples of complex (complex) compounds formed by ammonia as a result of addition reactions are given in and 201, as well as in Ch. XVIII. Above (p. 124), the interaction of a molecule with a hydrogen ion, leading to the formation of an ammonium ion, has already been considered:
In this reaction, ammonia serves as a proton acceptor and, therefore, from the point of view of the proton theory of acids and bases (p. 237), it exhibits the properties of a base. Indeed, reacting with acids that are in a free state or in solution, ammonia neutralizes them, forming ammonium salts. For example, with hydrochloric acid ammonium chloride is obtained:
The interaction of ammonia with water also leads to the formation of not only ammonia hydrates, but also partly of the ammonium ion:
As a result, the concentration of ions in the solution increases. That is why aqueous solutions of ammonia have an alkaline reaction. However, according to the established tradition, an aqueous solution of ammonia is usually denoted by the formula and called ammonium hydroxide, and the alkaline reaction of this solution is considered as the result of dissociation of molecules.
Ammonia is a weak base. At , its ionization equilibrium constant (see the previous equation) is . A one-molar aqueous solution of ammonia contains only 0.0042 equivalents of and ions; such a solution at has .
Most ammonium salts are colorless and highly soluble in water. In some of their properties, they are similar to salts of alkali metals, especially potassium (ions and have similar sizes).
Since an aqueous solution of ammonia is a weak base, ammonium salts in solutions are hydrolyzed. Solutions of salts formed by ammonia and strong acids have a slightly acidic reaction.
Hydrolysis of the ammonium ion is usually written in this form:
However, it is more correct to consider it as a reversible transition of a proton from an ammonium ion to a water molecule:
When alkali is added to an aqueous solution of any ammonium salt, ions are bound by OH- ions into water molecules and the hydrolysis equilibrium shifts to the right. The process that occurs in this case can be expressed by the equation:
When the solution is heated, ammonia evaporates, which can be easily seen by the smell. Thus, the presence of any ammonium salt in a solution can be detected by heating the solution with alkali (ammonium reaction).
Ammonium salts are thermally unstable. When heated, they decompose. This decomposition can be reversible or irreversible. Ammonium salts, the anion of which is not an oxidizing agent or exhibits oxidizing properties only to a weak degree, decompose reversibly. For example, when heated, ammonium chloride, as it were, sublimates - it decomposes into ammonia and hydrogen chloride, which, on the cold parts of the vessel, recombine into ammonium chloride:
With the reversible decomposition of ammonium salts formed by non-volatile acids, only ammonia volatilizes. However, the decomposition products - ammonia and acid - when mixed, recombine with each other. Examples are the decomposition reactions of ammonium sulfate or ammonium phosphate.
Ammonium salts, the anion of which exhibits more pronounced oxidizing properties, decompose irreversibly: a redox reaction occurs, during which the ammonium is oxidized and the anion is reduced. Examples are the decay (§ 136) or decomposition of ammonium nitrate:
Ammonia and ammonium salts are widely used. As already mentioned, ammonia, even at low pressure, easily turns into a liquid. Since the evaporation of liquid ammonia absorbs a large number of heat (1.37), then liquid ammonia is used in various refrigeration devices.
Aqueous solutions of ammonia are used in chemical laboratories and industries as a weak volatile base; they are also used in medicine and in everyday life. But most of the ammonia produced in industry goes to the preparation of nitric acid, as well as other nitrogen-containing substances. Among the most important of these are nitrogen fertilizers, primarily ammonium sulfate and nitrate, and urea (p. 427).
Ammonium sulfate serves as a good fertilizer and is produced in large quantities.
Ammonium nitrate is also used as a fertilizer; the percentage of assimilable nitrogen in this salt is higher than in other nitrates or ammonium salts. In addition, ammonium nitrate forms explosive mixtures with combustible substances (ammonals) used for blasting.
Ammonium chloride, or ammonia, is used in dyeing, in calico printing, in soldering and tinning, and also in galvanic cells. The use of ammonium chloride in soldering is based on the fact that it helps to remove oxide films from the metal surface, so that the solder adheres well to the metal. When a strongly heated metal comes into contact with ammonium chloride, the oxides on the metal surface are either reduced or converted into chlorides. The latter, being more volatile than oxides, are removed from the metal surface. For the case of copper and iron, the main processes occurring in this case can be expressed by the following equations:
The first of these reactions is redox: copper, being less active metal than iron, is reduced by ammonia, which is formed when heated.
Liquid ammonia and solutions of ammonium salts saturated with it are used as fertilizers. One of the main advantages of such fertilizers is their high nitrogen content.
Back forward
Attention! The slide preview is for informational purposes only and may not represent the full extent of the presentation. If you are interested in this work, please download the full version.
Type of lesson: lesson with multimedia
Lesson Objectives:
- Tutorials: To systematize students' knowledge about salts; formation at the interdisciplinary level of a system of knowledge about ammonium salts, which have a huge practical value.
- Developing: develop practical skills in conducting qualitative reactions to ammonium salts; the ability to analyze what is seen; development logical thinking; development of cognitive interest in the performance of theoretical and practical tasks.
- Educational: To increase the cognitive activity and activity of students; developing the ability to work in a team.
Equipment and reagents of the lesson:
1. On the teacher's desk: a solution of hydrochloric acid HCl; ammonium hydroxide NH 4 OH; ammonium chloride NH 4 Cl; sodium chloride NaCl; water H 2 O; litmus; phenolphthalein; ammonium dichromate (NH 4) 2 Cr 2 O 7.
2. On the students' table: ammonium sulfate (NH 4) 2 SO 4; sulphuric acid H2SO4; barium chloride BaCl; ammonium chloride NH 4 Cl; sodium hydroxide NaOH;
3.Interactive board.
Main questions:
- Determination of ammonium salts.
- The role of ammonium salts in national economy.
- Physical and chemical properties of ammonium salts.
- Getting ammonium salts.
- Qualitative reactions to ammonium salts.
Basic concepts: Ammonium cation, ammonium salts.
During the classes
1. Organizational moment
The teacher checks the readiness for the lesson, informs the topic of the lesson.
2. Checking basic knowledge (10 min)
On the teacher's table are substances (salts) in a glass container.
Teacher: This container contains an amazing substance. Once it was considered "God's grace", a symbol of well-being.
:. But it can also destroy the living, because of it even the sea can become dead.
Together with this it is difficult to enumerate, wherever it is applied.
What is in this bottle?
(Suggested answer is salt.)
What substances do we refer to as salts?
Training exercise:
From the following substances, select salts and name them:
KCl NaOH KOH CO2 H2SO4 Ba(NO3)2 CuSO4 MgO NH4Cl H 2 S AgNO3 (NH 4) 2 SO 4
Teacher: What unusual salts did you meet?
These salts contain a complex cation - the ammonium cation.
The teacher asks the class to formulate the concept of ammonium salt (salts consisting of ammonium cations and acid residue anions).
Teacher: Where do you think these salts can be used? Why?
Students: In agriculture, as they contain a vital element for plants - nitrogen.
For a comprehensive description of the practical significance of ammonium salts, it is advisable to hear a mini report from students.
3. Learning new material (15 min)
Teacher: Let's study the physical and chemical properties of ammonium salts in practice.
What is common in the physical properties of salts and ammonium salts?
Students: solid, white, crystalline substances, highly soluble in water, electrolytes.
Teacher: Check the solubility of ammonium sulfate in practice, write down the physical properties in a notebook ( conducting an experiment).
Teacher: Consider the chemical properties of ammonium salts.
Let's remember general properties salts:
(A reference summary is compiled in the notebook) .
A) dissociation - we write the equations for the dissociation of salts
- ammonium chloride
- ammonium sulfate
B) Interaction with acids
2 NH 4 Cl + H 2 SO 4 (NH 4) 2 SO 4 + 2 HCl
Perform the experiment, indicate the signs of the reaction ( conducting an experiment).
C) Interaction with alkalis.
We put phenolphthalein paper into the test tube and observe the color change ( conducting an experiment)
Conclusion: this reaction is qualitative on ammonium salts
D) Interaction with salts
NH 4 Cl + AgNO 3 NH 4 NO 3 + AgCl
Students do an experiment, write down the reaction equation and check them on their own with the equation on the slide ( conducting an experiment).
Creative task: Determine which of the three test tubes contains ammonium sulfate. Write down the equations of the reactions performed ( conducting an experiment).
Specific properties of salts:
D) Decomposition of ammonium salts
Demonstration experience: decomposition of ammonium dichromate; ammonium chloride:
NH 4 Cl NH 3 + HCl
(NH 4) 2 Cr 2 O 7 N 2 + Cr 2 O 3 + 4H 2 O
E) Hydrolysis of ammonium salts
NH 4 Cl + H 2 O NH 4 OH + HCl
Demonstration experience.
Conclusion: alkaline medium, litmus - blue, phenolphthalein - raspberry.
Teacher: Remember in what ways you can get salt.
Students: In the interaction of a base and an acid; salt and salt; salts and acids.
The teacher demonstrates the experiments, the students write down the reference notes using the slide.
A) NH 4 OH + HCl NH 4 Cl + H 2 O
B) (NH 4) 2 SO 4 + BaCl 2 BaSO 4 + 2 NH 4 Cl
C) (NH 4) 2 CO 3 + 2HCl 2 NH 4 Cl + H 2 O + CO 2
Conclusion: when writing equations, it is necessary to observe the condition of irreversibility of chemical reactions.
4. Consolidation of the material covered (15 min)
Exercise number 1.
Choose and name ammonium salts:
I option II option NaNO 3 BaCl2
Pair check.
Self-test.
NH 3 + HCl NH 4 Cl
2NH 3 + H 2 SO 4 (NH 4) 2 SO 4c) 3
react with sulfuric acid
The correct answer on the slide is marked with dots in the figure, then the dots are connected to form a smile.
Students compare their answers with the sample on the screen, try to independently analyze the mistakes made. The teacher corrects the students' answers.
Exercise number 4.(A game exercise that develops the desire of the children to find the right answer, having received which it will be possible to open the safe).
"Golden Key"
Determine the code for the safe.
List the sequence of numbers (in ascending order) that determine the properties of ammonium sulfate.
Test:
- Dissolve in water.
- Not electrolytes.
- White crystalline substance.
- Smells like ammonia.
- Reacts with barium chloride.
- Reacts with calcium hydroxide.
- Decomposes when heated.
- I DON'T KNOW THE WORD
- reacts with phosphoric acid.
- Reacts with UNKNOWN NAME
Answer: 1345678
The teacher asks the children to write down possible reaction equations.
5. Homework
Creative task: White salt, soluble in water, with silver nitrate forms a white cheesy precipitate, the combustion of which produces nitrogen. Name the salt, write the reaction equations in molecular and ionic form.
6. Lesson conclusions (3min)
Completion of the lesson in an interesting creative form will give good mood each child, and improve the quality of assimilation of the material studied in the lesson.
Compilation of a cinquain (an interesting non-rhyming poem that requires information in slick terms, which allows you to describe what you saw and heard):
Students write cinquain, working in pairs, using a textbook and a supporting note.
- ammonium salts
- useful, important
- Turning deserts into oases
- React like all salts with salts, acids and alkalis
- They decompose and are used in agriculture.
7. Summing up the lesson, the teacher gives the words:“The thinking mind does not feel happy until it succeeds in linking together disparate facts” (Hevelsi).
Saltpeter- natural nitrates - was known in China in the first centuries of our era; it was used to make gunpowder and hold fireworks. Later it is mentioned in writings (Latin names - nitro or sal nitri). By heating saltpeter with iron sulfate, alchemists received, which for a long time was called in Latin aqua fortis (“strong water”; in Russian texts, the term “ strong vodka»).
Pure nitric acid was first obtained by a German chemist Johann Rudolf Glauber acting on saltpeter with vitriol oil (concentrated):
KNO 3 + H 2 SO 4 \u003d KHSO 4 + HNO 3
Atacama Desert. Mining site for Chilean saltpeter He also discovered that the interaction of nitric acid with potash K 2 CO 3 forms pure potassium nitrate. This discovery was of great practical importance, because earlier saltpeter, necessary for the production of gunpowder, was imported to Europe from the countries of the East, and also isolated from salt deposits on the walls of stables or from saltpeter pits, where it was formed under the action of microorganisms like final product oxidation of nitrogen-containing organic compounds.
When calcining a mixture of saltpeter NaNO 3, ferrous sulfate FeSO 4 ∙7H 2 O, potassium alum KAl (SO 4) 2 ∙12H 2 O and ammonia NH 4 Cl, alchemists managed to obtain a liquid that dissolved even the “king of metals” -. Therefore, it was called aqua regia, which means " royal water" or " aqua regia". Royal vodka is a yellow liquid formed by mixing three volumes and one volume of nitrogen. Even platinum dissolves easily in aqua regia.
Nitrogen was independently discovered in late XVIII v. several scientists. English explorer Henry Cavendish received "mephitic air" (as he called nitrogen), repeatedly passing air over hot coal (thereby removing oxygen), and then through a solution to absorb the formed.
Henry Cavendish Compatriot of Cavendish Joseph Priestley described the formation of a gas that does not support combustion and respiration - "phlogistic air" - while observing the burning of a candle in a closed vessel.
Finally, another English scientist, Daniel Rutherford also received nitrogen from the air. Unlike Cavendish and Priestley, he immediately, in 1772, published a work where he described the production and properties of the "suffocating air" he had isolated. Therefore, it is Rutherford who is considered the discoverer of nitrogen.
In nature, the largest amount of nitrogen is in unbound form in the air. The main composition of atmospheric air was determined by A.L. Lavoisier, at whose suggestion the new element was called nitrogen. This name is composed of the Greek word "zoe" ("life") and the prefix "a" - ("non-") and means "lifeless", "not giving life." The Latin name for nitrogen is Nitrogenium, which translates as "forming nitrate."
Minerals that contain nitrogen are rare, for example, Chilean saltpeter NaNO 3, whose deposits stretch along the coast of Chile and Peru for a distance of over 3600 km. V late XIX v. its production was approximately 0.5 tons per year. It is no coincidence that entrepreneurs and scientists had fears that its reserves would soon run out. This prompted chemists to develop technologies for the binding of nitrogen in the air.
In industry, nitrogen is obtained from liquid air. To do this, the air is transferred to liquid state, and at a temperature of – 196 0 C, nitrogen evaporates.
Nitrogen is produced in the laboratory decomposition of ammonium nitrite NH 4 NO 2 when heated:
NH 4 NO 2 \u003d N 2 + H 2 O
Physical properties
A liquid nitrogen Nitrogen- gas without color, taste and smell (t pl = -210 0 C, t bp = -196 0 C), slightly soluble in water. Free nitrogen is chemically inert due to its high strength molecules N 2 where the atoms are triple bonded. Therefore, nitrogen hardly enters into chemical reactions, does not support combustion and respiration.
Characteristic oxidation states:
— 3 0 +1 +2 +3 +4 +5
NH 3 N 2 N 2 O NO N 2 O 3 NO 2 N 2 O 5
Chemical properties
V chemical reactions Nitrogen can be both an oxidizing agent and a reducing agent.
Nitrogen interacts as an oxidizing agent:
N 2 + 3Ca \u003d Ca 3 N 2
Nitrogen interacts as a reducing agent:
N 2 + F 2 \u003d 2NF 3
Application
Nitrogen is the feedstock for the production of ammonia.
Ammonia
Ammonia- a colorless gas with a pungent odor, highly soluble in water. In one liter of water at a temperature of 20 0 C, 700 liters of ammonia dissolve. This solution is called ammonia water or ammonia.
Chemical properties
Acid-base properties
The nitrogen atom in the ammonia molecule has an unshared electron pair, which can participate in the formation of a donor-acceptor bond. In particular, the nitrogen atom in NH 3 is able to attach the hydrogen ion H + . Substances whose molecules are capable of attaching hydrogen ions have basic properties. Therefore, ammonia has the main properties:
- interaction of ammonia with water:
NH 3 + HOH ⇄ NH 4 OH ⇄ NH 4 + + OH -
- interaction with hydrogen halides:
NH 3 + HCl ⇄ NH 4 Cl
- interaction with (as a result, medium and acidic salts are formed):
NH 3 + H 3 PO 4 = (NH 4) 3 PO 4; (NH 4) 2 HPO 4 ; (NH 4) H 2 PO 4
- ammonia interacts with some metals to form complex compounds - ammoniates:
CuSO 4 + 4NH 3 \u003d SO 4 Copper (II) tetraammine sulfate
AgCl + 2NH 3 \u003d Cl Silver (I) diamine chloride
Redox properties
In the ammonia molecule, nitrogen has an oxidation state of 3, therefore, in redox reactions, it can only donate electrons and is only a reducing agent.
- ammonia restores some of them:
2NH 3 + 3CuO = N 2 + 3Cu + 3H 2 O
- ammonia is oxidized without a catalyst to nitrogen:
4NH 3 + 3O 2 \u003d 2N 2 + 6H 2 O
- ammonia in the presence of a catalyst is oxidized to nitrogen monoxide NO:
4NH 3 + 5O 2 \u003d 4NO + 6H 2 O
ammonium salts
ammonium chloride When ammonia or ammonium hydroxide reacts with ammonium salts:
All ammonium salts are highly soluble in water. Ammonium salts have The special properties of ammonium salts include the reactions of their thermal decomposition, which proceed differently, depending on the nature of the anion, for example:
(NH 4) 2 SO 4 \u003d NH 3 + NH 4 HSO 4
NH 4 NO 3 \u003d N 2 O + 2H 2 O
NH 4 Cl \u003d NH 3 + HCl
The reaction of interaction of ammonium salts is qualitative reaction to the ammonium cationNH 4 + :
NH 4 Cl + NaOH = NaCl + NH 3 + H 2 O
NH 4 + + OH - = NH 3 + H 2 O
The released ammonia is determined by the smell or by the blue color of wet litmus paper.
The use of ammonia and ammonium salts
You can download essays on other topics
Topic 2 Grade 9
Lesson 34
Lesson topic: Ammonium salts.
Lesson Objectives: educational
- to study the composition of ammonium salts, to repeat the general chemical properties of salts using the example of ammonium salts, to reveal the specific properties of these salts due to the ammonium ion; explore practical use ammonium salts; deepen the basic chemical concepts: substance, chemical reaction; study the practical significance of ammonium salts.
developing - to develop in students the ability to compare, analyze and apply information from other areas of knowledge, develop communication skills, the ability to present the results of group activities;
educational - contribute to education environmental literacy students have an active life position.
Lesson type:learning new material.
Teaching methods:partially exploratory, visual,Forms of organization of cognitive activity:group, frontal, practical.
Technical means learning:computer, projector, screen
Working methods: independent work with the textbook, work in pairs.
Equipment and reagents: solutions - barium chloride, sodium hydroxide, hydrochloric acid, ammonium carbonate, ammonium chloride, ammonium sulfate a glass of water;ammonium hydroxide, nitric acid, ammonium sulfate, ammonium chloride, ammonium carbonate, silver nitrate, potassium nitrate, hydrochloric acid, sodium hydroxide;
test tubes, test tube stand, spirit lamp, cotton wool, test tube holder, phenolphthalein paper.
PROCEDURE OF THE LESSON: 1. Organizational part of the lesson.
2. Testing students' knowledge.
Questions and tasks of the survey.
1. Task: An excess of calcium hydroxide was added to 400 g of a solution with a mass fraction of ammonium chloride of 8%. Determine the amount of gas released.
2. Questions: 1. The structure of the ammonia molecule.
2. List the physical properties of ammonia.
3.Chemical properties ammonia.
4. List the areas of application of ammonia.
3. The task "the third extra"
TO 3 RO 4 , HCL , H 2 SO 4
Ba(OH) 2, NaNO 3 , NaOH
K 2 O CO 2 , MgSO 4
4. Test (1st option - nitrogen, 2nd option - ammonia)
1. Gaseous under normal conditions
2.No odor
3.Colorless
4. Slightly soluble in water
5. Nitrogen oxidation state -3
6.Does not burn in the air
7. Burns in oxygen
8. Interacts with acids to form salts
9. In a molecule between atoms, a covalent polar bond
10. Relationship with hydrogen in the presence of a catalyst
11. It is the most important biogenic element.
12. The aqueous solution has an alkaline environment
13. It exhibits predominantly restorative properties
14.10% solution of it is called ammonia
(We exchange notebooks, check).
1, 2, 3, 4, 6, 10, 11, 13
1, 3, 5, 7, 8, 9, 12, 13
3. Study of program material.
1. Ammonium salts - it complex substances containing in its composition ammonium ions, combined with acidic residues.
ammonium salt - salts containing monovalent ammonium ion NH 4 + ; in structure, color and other properties, they are similar to the corresponding potassium salts. All ammonium salts are soluble in water and completely dissociate in aqueous solution. Ammonium salts exhibit the general properties of salts. Under the action of alkali, gaseous NH is released 3 . All ammonium salts decompose when heated. They are obtained by the interaction of NH 3 or NH4 OH with acids. Ammonium nitrate (ammonium nitrate) NH 4 NO 3 used as a nitrogen fertilizer and for the manufacture explosives- ammonites, ammonium sulfate (NH 4) 2 SO 4 applied as cheap nitrogen fertilizer, ammonium bicarbonate NH4HCO 3 and ammonium carbonate (NH 4) 2 CO 3 used in Food Industry, in dyeing fabrics, in the production of vitamins, in medicine; ammonium chloride (ammonia) NH 4 Cl is used in galvanic cells (dry batteries), in soldering and tinning, in the textile industry, as a fertilizer, and in veterinary medicine.
2. General formula ammonium salts.
NH 4 R; (NH 4) n R , where R - acid residue.
V NH 4 CL has an ammonium cation
3. Physical properties of ammonium salts.
Ammonium salts are solid, crystalline substances, highly soluble in water.
4. Chemical properties of ammonium salts.
Properties shared with other salts
Specific properties
1.Strong electrolytes
NH 4 N O 3 \u003d NH 4 + + N O 3 -
2. React with acids - exchange reaction
(NH 4) 2 CO 3 + 2HCl \u003d 2NH 4 Cl + CO 2 + H 2 O
3. React with other salts
(NH 4) 2 SO 4 + BaCl 2 \u003d 2NH 4 Cl + Ba SO 4
4.Subject to hydrolysis
NH 4 Cl + H 2 O.
It is the salt of a weak base and a strong acid. The chain breaks at the weakest link. Hydrolysis proceeds at the ammonium cation.
1.Decompose at high temperature
a) if the acid is volatile
NH 4 Cl \u003d NH 3 + HCl
NH 4 HCO 3 → NH 3 + H 2 O + CO 2
b) if the acid is non-volatile
(NH 4) 2 SO 4 \u003d?
c) if the acid is non-volatile and the anion exhibits oxidizing properties
(NH 4 ) 2 Cr 2 O 7 = Cr 2 O 3 + N 2 + 4H 2 O
NH 4 NO 3 \u003d N 2 O + 2 H 2 O
2. React with alkalis
NH 4 Cl + NaOH \u003d NaCl + NH 3 + H 2 O
This is a qualitative reaction to ammonium salts.
3. With acids and salts (exchange reaction)
a) (NH4) 2 CO 3 + 2 HCl → 2NH 4 Cl + H 2 O + CO 2
2NH 4 + + CO 3 2- + 2H + + 2Cl - → 2NH 4+ + 2Cl - + H 2 O + CO 2
CO 3 2- + 2H + → H 2 O + CO 2
b) (NH4) 2 SO 4 + Ba(NO3) 2 → BaSO 4 + 2NH 4 NO 3
2NH 4 + + SO 4 2- + Ba 2+ + 2NO 3 - → BaSO 4 + 2NH 4 + + 2NO 3 -
Ba 2+ + SO 4 2- → BaSO 4
4. Ammonium salts undergo hydrolysis (as a salt of a weak base and a strong acid) - an acidic environment:
NH4Cl + H2O → NH4OH + HCl
NH4+ + H2O → NH4OH + H+
5. Strong electrolytes (dissociate in aqueous solutions)
NH 4 Cl → NH 4 + + Cl -
CONCLUSION: 1) Ammonium salts are electrolytes that dissociate into the ammonium cation NH
4
+
and acid residue anions.
2)
They exhibit properties:
a) Common with salts -
interact with acids, salts, if a precipitate or gas is formed.
b) Specific -
interact with alkalis to form ammonia, decompose when heated, are highly soluble in water and are electrolytes, show an acidic environment during hydrolysis or hydrolysis is complete.
It is interesting:
The name "ammonium" was proposed in 1808. Humphrey Davy. latin word ammonium once meant "salt from Ammonium". Ammonia is a region of Libya. There was a temple of the Egyptian god Ammon, after whom the whole region was called. In Ammonia, ammonium salts have long been obtained by burning camel dung. During the decomposition of salts, a gas was obtained, which is now called ammonia. In 1787 The Commission on Chemical Nomenclature named the gas ammoniac. Russian chemist Zakharov shortened this name to "ammonia".
A solution of ammonia in water is called ammonia. "Ammonia" because it can be obtained from ammonia NH 4 Cl. But why alcohol? The Latin spiritus means "spirit", "soul". Obviously, a chemist unknown to us, who dissolved ammonia obtained from ammonia in water, called the pungent liquid "the soul of ammonia."
The name "nitrates" comes from the name of the city of Nitria in Upper Egypt, where the mineral NH 4 NO 3 was first found.
4. Methods for obtaining ammonium salts.
1. Ammonium salts are obtained by reacting ammonia with acids.
2. When ammonia water interacts with acids.
5. Critical areas the use of ammonium salts.
like fertilizer
For the production of explosives
Ammonium bicarbonate and ammonium carbonate in the food industry as a leavening agent for dough.
When dyeing fabrics in the textile industry
In the production of vitamins
In medicine
When soldering
in dry batteries
When dressing leather
In pyrotechnics
Conclusions:
Ammonium salts are formed by ammonium cations and anions of acid residues
By physical properties they are similar to alkali metal salts, especially potassium
A qualitative reaction to the ammonium cation is interaction with alkalis when heated, the gas released has a characteristic odor and colors phenolphthalein paper in a crimson color.
4. Consolidation of the studied material
Consolidation of the studied material can be carried out in the form of a differentiated individual independent work learners by choice.
OPTION 1
Write the full and abbreviated ionic equations for reactions occurring between substances:
-ammonium chloride and silver nitrate;
ammonium carbonate and hydrochloric acid;
Ammonium nitrate and sodium hydroxide.
OPTION 2
Add the reaction equations in full and abbreviated ionic form:
(NH 4) 2 SO 4 +? → NH 4 CI + BaSO 4 ↓
NH4CI+? →? +? + NH3
(NH 4) 2 S + HCI → ? +?
OPTION 3
Write the full and abbreviated ionic equations for the reactions that occur between the following pairs of substances:
- ammonium salt and other salt;
Ammonium salt and alkali;
Ammonium salt and acid.
5. Homework:§ 26, exercise 1-4 (in writing)
Ammonium is one of the many nitrogen compounds. Its salts have a number of interesting properties and find practical applications in many areas. human activity. Chemistry is the study of the properties of this element. Ammonium salts are studied in the section on the interaction of nitrogen with other chemical elements.
What is ammonium
To find out what ammonium is, you should take a closer look at the principle of combining nitrogen and carbon atoms. The ammonia molecule is written as NH 3. The nitrogen atom is bound by its covalent bonds with three protons. Due to internal structure nitrogen, one bond remains undistributed.
Therefore, NH 3 actively enters into various covalent bonds with other elements, using an unshared electron pair. If a hydrogen nucleus enters the compound, an ammonium ion is formed. The reaction scheme is shown below:
As can be seen, in this reaction, the ammonia molecule is an acceptor of one proton and thus behaves like a base. Ammonium does not exist in its free form, as it almost instantly decomposes into hydrogen and ammonia. Ammonium salts are obtained as a result of the interaction of this element with other substances. As practical experiments show, ammonium enters into various compounds with acids, neutralizing them and forming ammonium salts. For example, in the case of reaction with hydrochloric acid, one of the salts of this element is formed:
NH 3 + HCl = NH 4 Cl
As a result of the reaction, ammonium salt chloride is obtained.
Interaction with water
Ammonium interacts well with water. As a result of the reaction, ammonia hydrates are obtained with an increased concentration of OH - . Chemical record of the reaction:
NH 3 + H 2 O → NH 4 + OH -
Since the number of hydroxo group ions is extremely large, aqueous solutions of ammonia have an alkaline reaction. However, according to the old chemical habit, an aqueous solution of ammonia is written as NH 4 OH. This substance is called ammonium hydroxide, and the alkaline reaction of this compound is considered in the form of dissociation of molecules into which ammonia is decomposed.
Ammonium salts. Properties and main characteristics
Most of the NH 4 salts are practically colorless and quite soluble in water. This compound has many properties of metals, therefore ammonium salts behave in the same way as salts of various metals. Here are some examples of such similarity:
NH 4 salts are good electrolytes. They undergo hydrolysis in various solutions. This reaction can be traced on the example of the dissociation of ammonium chloride:
NH 4 Cl \u003d NH 4 + + HCl -
subject to hydrolysis. The result is the reaction of a salt of a weak base and a strong acid:
have ionic crystal lattice, have electrical conductivity;
Can't stand high temperatures and break down into components.
Irreversible and reversible processes
The decomposition of ammonium salts under the influence of temperatures can be irreversible, or it can be a reversible process. If the salt anion exhibits mild oxidizing properties, the salt decomposes reversibly. A classic example of such a reaction is ammonium chloride: as the reaction temperature rises, it eventually decomposes into its own original elements- hydrogen chloride, as well as ammonia. If the walls of the vessel are not heated, plaque appears on them. This is how ammonium chloride is generated.
Other salts of this element, in which the anion has pronounced oxidizing properties, decompose irrevocably. A standard example of such a reaction is the decomposition of ammonium nitrate, which looks like this:
NH 4 NO 3 \u003d N 2 O + H 2 O
Since one of the interaction products leaves its field, the reaction stops.
The use of ammonia and ammonium salts
A significant proportion of industrially produced ammonia is used in freezing and refrigeration plants. Ammonium salts are used in Everyday life and in medicine. But the vast majority of ammonia is used to produce nitric acid and various nitrogen-containing compounds, primarily various mineral fertilizers.
Nitrogen fertilizers
The most famous nitrogen derivative salts, the use of which in economic activity it is extremely important - it is ammonium sulfate, ammonium nitrate, ammonium chloride. Nitrogen is an essential component of proteins. This element is essential for the existence of any living organism. Plants extract nitrogen from fertile soil, where this element is found predominantly in a bound form. Nitrogen usually occurs as ammonium salts and nitric acid compounds. Dissolving in moist soil, these inorganic compounds enter the organisms of plants and are processed by them into various proteins and amino acids. Animals and humans cannot assimilate nitrogen either in its free form or as its simple compounds. They need protein to feed and grow. integral part which must be nitrogen. Only with the participation of plants we get the element so necessary for us for life and health.
Soils in the natural environment contain a small amount of nitrogen. After the harvest of each crop, along with the plants, the small amount of nitrogen that was previously in the ground is carried away. To speed up the process of soil regeneration, nitrogenous fertilizers are used.
Ammonium sulfate. The formula of this compound is (NH4) 2 SO 4. This ammonium salt serves as the basis for many fertilizers.
ammonium nitrate. The formula of this substance is NH 4 NO 3. It is also a well-known fertilizer that is well absorbed by plants. In addition to agricultural use, ammonium nitrate is used in the military and mining industries - explosive mixtures (ammonals) used for demolition work are made on its basis.
ammonium chloride
ammonium chloride. Well known as ammonia. His chemical formula- NH4Cl. This compound is well known in the production of paint and varnish products, in the textile business, ammonia is used and in galvanic cells. Ammonium chloride is well known to shareholders and tinkers. In their work, they often use ammonium chloride salts. The use of this substance helps to remove the thinnest oxide films from the surface of metals. The touch of a heated metal to ammonia causes a corresponding reaction of oxides - they either turn into chlorides or are reduced. Chlorides quickly evaporate from the metal surface. The reaction process for copper can be written as follows:
4CuO + 2NH 4 Cl \u003d 3Cu + 2CuCl 2 + N 2 + 4H 2 O.
Ammonia in liquid form and strong solutions of ammonium salts are also used as nitrogen fertilizers - the nitrogen content in them is higher than in solid fertilizers, and it is better absorbed by plants.
