A colorless gas with a pungent odor, ammonia NH 3 not only dissolves well in water and releases heat. The substance actively interacts with H 2 O molecules to form a weak alkali. The solution received several names, one of them is ammonia water. The compound has amazing properties, which include the method of formation, composition and

Ammonium ion formation

The formula of ammonia water is NH 4 OH. The substance contains the NH 4 + cation, which is formed by non-metals - nitrogen and hydrogen. The N atoms in the ammonia molecule use only 3 of the 5 outer electrons to form, leaving one pair unclaimed. In a highly polarized water molecule, the hydrogen protons H+ are weakly bound to oxygen, one of them becomes a donor of a free nitrogen electron pair (acceptor).

An ammonium ion is formed with one positive charge and a special type of weak covalent bond - donor-acceptor. In its size, charge and some other features, it resembles a potassium cation and behaves like a chemically unusual compound that reacts with acids and forms salts that are of great practical importance. Names that reflect the characteristics of the preparation and properties of the substance:

• ammonium hydroxide;
• ammonia hydrate;
• caustic ammonium.

Precautionary measures

Care must be taken when working with ammonia and its derivatives. Important to remember:

1. Ammonia water has an unpleasant odor. The released gas irritates the mucous surface of the nasal cavity, eyes, and causes coughing.
2. When stored in loosely closed bottles or ampoules, ammonia is released.
3. Even small amounts of gas in solution and air can be detected without instruments, only by smell.
4. The ratio between molecules and cations in a solution changes at different pH levels.
5. At a value of about 7, the concentration of the toxic gas NH 3 decreases, and the amount of NH 4 + cations, which are less harmful to living organisms, increases

Preparation of ammonium hydroxide. Physical properties

When ammonia dissolves in water, ammonia water is formed. The formula of this substance is NH 4 OH, but in fact there are ions present at the same time

NH 4 + , OH - , NH 3 and H 2 O molecules. In the chemical reaction of ion exchange between ammonia and water, an equilibrium state is established. The process can be reflected using a diagram in which oppositely directed arrows indicate the reversibility of the phenomena.

In the laboratory, ammonia water is obtained through experiments with nitrogen-containing substances. When ammonia is mixed with water, a clear, colorless liquid is obtained. At high pressures, the solubility of the gas increases. Water releases more ammonia dissolved in it as the temperature rises. For industrial needs and agriculture, a 25% substance is obtained on an industrial scale by dissolving ammonia. The second method involves using a reaction with water.

Chemical properties of ammonium hydroxide

When two liquids come into contact - ammonia water and hydrochloric acid - they become covered in clouds of white smoke. It consists of particles of the reaction product - ammonium chloride. With a volatile substance such as hydrochloric acid, the reaction occurs directly in the air.

Slightly alkaline chemical properties of ammonia hydrate:

1. The substance dissociates reversibly in water to form ammonium cation and hydroxide ion.
2. In the presence of the NH 4 + ion, a colorless solution of phenolphthalein turns crimson, as in alkalis.
3. Chemical interaction with acids leads to the formation of ammonium salts and water: NH 4 OH + HCl = NH 4 Cl + H 2 O.
4. Ammonia water enters into ion exchange reactions with metal salts, which correspond to the formation of a water-insoluble hydroxide: 2NH 4 OH + CuCl 2 = 2NH 4 Cl + Cu(OH) 2 (blue precipitate).

Ammonia water: application in various sectors of the economy

The unusual substance is widely used in everyday life, agriculture, medicine, and industry. Technical ammonia hydrate is used in agriculture, the production of soda ash, dyes and other types of products. Liquid fertilizer contains nitrogen in a form that is easily absorbed by plants. The substance is considered the cheapest and most effective for application in the pre-sowing period for all agricultural crops.

The production of ammonia water requires three times less money than the production of solid granular nitrogen fertilizers. Hermetically sealed steel tanks are used to store and transport liquids. Some types of dyes and hair bleaching products are made using ammonium hydroxide. Every medical institution has preparations with ammonia - a 10% ammonia solution.

Ammonium salts: properties and practical significance

Substances that are obtained by reacting ammonium hydroxide with acids are used in economic activities. Salts decompose when heated, dissolve in water, and undergo hydrolysis. They enter into chemical reactions with alkalis and other substances. Chlorides, nitrates, sulfates, phosphates and

It is very important to follow the rules and safety measures when working with substances that contain ammonium ion. When stored in warehouses of industrial and agricultural enterprises, in subsidiary farms, there should be no contact of such compounds with lime and alkalis. If the seal of the packages is broken, a chemical reaction will begin with the release of poisonous gas. Anyone who has to work with ammonia water and its salts must know the basics of chemistry. Subject to compliance with safety requirements, the substances used will not cause harm to people and the environment.

Equivalent can be called a real or conditional particle of a substance that can replace, add, or be in some other way equivalent to one hydrogen ion in acid-base or ion exchange reactions or one electron in redox reactions.

The equivalent molar mass in most exchange reactions (which occur without changing the oxidation states of the elements involved) can be calculated as the ratio of the molar mass of the substance to the number of broken or formed bonds per one atom or one molecule during a chemical reaction.

The molar mass equivalent of the same substance can be different in different reactions.

The molar mass equivalent in redox reactions (which occur with a change in the oxidation states of the elements involved in them) can be calculated as the ratio of the molar mass of a substance to the number of electrons given or accepted per atom or molecule during a chemical reaction.

To find the equivalent mass of a substance in solution, use simple relationships:

For acid H n A m:

E k =M/n, Where n – number of Н+ ions in acid. For example, the equivalent mass of hydrochloric acid HCl is: E k=M/1, i.e. numerically equal to molar mass; the equivalent mass of phosphoric acid H 3 PO 4 is equal to: E k=M/3, i.e. 3 times less than its molar mass.

For the base Kn(OH)m:

E main =M/m, Where m – number of hydroxide-ones OH - in the base formula. For example, the equivalent mass of ammonium hydroxide NH 4 OH is equal to its molar mass: E main=M/1; the equivalent mass of copper (II) hydroxide Cu(OH) 2 is 2 times less than its molar mass: E main=M/2.

For salt K n A m:

E s =M/(n×m), Where n and m, respectively, number of salt cations and anions. For example, the equivalent mass of aluminum sulfate Al 2 (SO 4) 3 is: E s=M/(2×3)=M/6.

Law of equivalents - for every 1 equivalent of one substance in a reaction there is 1 equivalent of another substance.

From the law of equivalents it follows that The masses (or volumes) of reacting and resulting substances are proportional to the molar masses (molar volumes) of their equivalents. For any two substances related by the law of equivalents, we can write:

Where m 1 and m 2 – masses of reagents and (or) reaction products, g;

E 1, E 2– molar masses of equivalents of reagents and (or) reaction products, g/mol;

V 1 , V 2 – volumes of reagents and (or) reaction products, l;

EV 1, EV 2– molar volumes of equivalents of reagents and (or) reaction products, l/mol.

Gaseous substances, in addition to the molar mass of the equivalent, have molar volume equivalent (EV -volume occupied by molar mass equivalent or volume of one mole equivalent). At no. EV(O 2) = 5.6 l/mol , EV(H 2) = 11.2 l/mol ,

Task 1. The combustion of a mass of 12.4 g of an unknown element consumed a volume of 6.72 liters of oxygen. Calculate the element equivalent and determine which element was taken in the given reaction.

According to the law of equivalents

EV(O 2) – equivalent volume of oxygen equal to 5.6 l

E(element) = =10.3 g/mol-equiv

To determine an element, you need to find its molar mass. The valence of an element (V), molar mass (M) and equivalent (E) are related by the relation E = , hence M = E∙V, (where B is the valency of the element).

In this problem, the valence of an element is not indicated, therefore, when solving it is necessary to use the selection method, taking into account the rules for determining valency - an element located in the odd (I, III, V, VII) group of the periodic table can have a valency equal to any odd number, but no more than group number; an element located in an even (II, IV, VI, VIII) group of the periodic table can have a valence equal to any even number, but not more than the group number.

M = E ∙ V = 10.3 ∙ I = 10.3 g/mol

M = E ∙ V = 10.3 ∙ II = 20.6 g/mol

There is no element with atomic mass 10.3 in the periodic table, so we continue the selection.

M = E ∙ V = 10.3 ∙ III = 30.9 g/mol

This is the atomic mass of element number 15, this element is phosphorus (P).

(Phosphorus is located in group V of the periodic table; the valence of this element can be equal to III).

Answer: the element is phosphorus (P).

Task 2. 5.6 g of potassium hydroxide was used to dissolve 3.269 g of unknown metal. Calculate the metal equivalent and determine which metal was taken for this reaction.

According to the law of equivalents:

The equivalent of a base is defined as the ratio of its molar mass to the number of OH - groups in the base: M(KOH)=Ar(K)+ Ar(O)+ Ar(H) =39+16+1 =56 g/mol

E(KOH) = = 56 g/mol

Metal equivalent E(Me) = = = 32.69 g/mol-equiv

In this problem, the valency of the element is not indicated, so when solving it is necessary to use the selection method, taking into account the rules for determining valency. Valency is always equal to integers, M = E ∙ V = 32.69 ∙ I = 32.69 g/mol

There is no element with atomic mass 10.3 in the periodic table, so we continue the selection.

M = E ∙ V = 32.69 ∙ II = 65.38 g/mol.

This is the molar mass of the element zinc (Zn).

Answer: metal - zinc, Zn

Task 3. The metal forms an oxide in which the mass fraction of metal is 70%. Determine which metal is included in the oxide.

Let us take the mass of the oxide equal to 100 g, then the mass of the metal will be equal to 70 g (i.e. 70% of 100 g), and the mass of oxygen will be equal to:

m(O)= m(oxide)-m(Me) = 100 – 70 =30 g

Let's use the law of equivalents:

, where E(O) = 8 g.

E(Me) = = 18.67 g/mol-equiv

M (Me) = E ∙ V = 18.69 ∙ I = 18.69 g/mol

M = E ∙ V = 18.69 ∙ II = 37.34 g/mol.There is no element with such a molar mass in the periodic table, so we continue the selection.

M = E ∙ V = 18.69 ∙ III = 56 g/mol.

This is the molar mass of the element Iron (Fe).

Answer: metal - Iron (Fe).

Task 4. Dibasic acid contains 2.04% hydrogen, 32.65% sulfur and 65.31% oxygen. Determine the valence of sulfur in this acid.

Let's take the mass of acid equal to 100 g, then the mass of hydrogen will be equal to 2.04 g (i.e. 2.04% of 100 g), the mass of sulfur is 32.65 g, the mass of oxygen is 65.31 g.

We find the equivalent of sulfur to oxygen using the law of equivalents:

, where E(O) = 8 g.

E (S) = = = 4 g/mol-eq

The valency of sulfur if all oxygen atoms are attached to sulfur will be equal to:

B = = = 8, therefore, oxygen atoms form eight chemical bonds in this acid. By definition, an acid is dibasic, which means that two bonds formed by oxygen atoms are associated with two hydrogen atoms. Thus, out of eight oxygen bonds, six bonds are used per compound with sulfur, i.e. The valency of sulfur in this acid is VI. One oxygen atom forms two bonds (valencies), so the number of oxygen atoms in an acid can be calculated as follows:

n(O) = = 4.

Accordingly, the acid formula will be H 2 SO 4.

The valency of sulfur in the acid is VI, the formula of the acid is H 2 SO 4 (sulfuric acid).

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Chemical formula

Molar mass of NH 4 OH, ammonium hydroxide 35.0458 g/mol

14.0067+1.00794 4+15.9994+1.00794

Mass fractions of elements in the compound

Using the Molar Mass Calculator

• Chemical formulas must be entered case sensitive
• Subscripts are entered as regular numbers
• The dot on the midline (multiplication sign), used, for example, in the formulas of crystalline hydrates, is replaced by a regular dot.
• Example: instead of CuSO₄·5H₂O in the converter, for ease of entry, the spelling is used CuSO4.5H2O.

Molar mass calculator

Mole

All substances are made up of atoms and molecules. In chemistry, it is important to accurately measure the mass of substances that react and result from it. By definition, the mole is the SI unit of quantity of a substance. One mole contains exactly 6.02214076×10²³ elementary particles. This value is numerically equal to Avogadro's constant N A when expressed in units of mol⁻¹ and is called Avogadro's number. Amount of substance (symbol n) of a system is a measure of the number of structural elements. A structural element can be an atom, molecule, ion, electron, or any particle or group of particles.

Avogadro's constant N A = 6.02214076×10²³ mol⁻¹. Avogadro's number is 6.02214076×10²³.

In other words, a mole is an amount of substance equal in mass to the sum of the atomic masses of atoms and molecules of the substance, multiplied by Avogadro's number. The unit of quantity of a substance, the mole, is one of the seven basic SI units and is symbolized by the mole. Since the name of the unit and its symbol are the same, it should be noted that the symbol is not declined, unlike the name of the unit, which can be declined according to the usual rules of the Russian language. One mole of pure carbon-12 is equal to exactly 12 g.

Molar mass

Molar mass is a physical property of a substance, defined as the ratio of the mass of this substance to the amount of substance in moles. In other words, this is the mass of one mole of a substance. The SI unit of molar mass is kilogram/mol (kg/mol). However, chemists are accustomed to using the more convenient unit g/mol.

molar mass = g/mol

Molar mass of elements and compounds

Compounds are substances consisting of different atoms that are chemically bonded to each other. For example, the following substances, which can be found in any housewife’s kitchen, are chemical compounds:

• salt (sodium chloride) NaCl
• sugar (sucrose) C₁₂H₂₂O₁₁
• vinegar (acetic acid solution) CH₃COOH

The molar mass of a chemical element in grams per mole is numerically the same as the mass of the element's atoms expressed in atomic mass units (or daltons). The molar mass of compounds is equal to the sum of the molar masses of the elements that make up the compound, taking into account the number of atoms in the compound. For example, the molar mass of water (H₂O) is approximately 1 × 2 + 16 = 18 g/mol.

Molecular mass

Molecular mass (the old name is molecular weight) is the mass of a molecule, calculated as the sum of the masses of each atom that makes up the molecule, multiplied by the number of atoms in this molecule. Molecular weight is dimensionless a physical quantity numerically equal to molar mass. That is, molecular mass differs from molar mass in dimension. Although molecular mass is dimensionless, it still has a value called the atomic mass unit (amu) or dalton (Da), which is approximately equal to the mass of one proton or neutron. The atomic mass unit is also numerically equal to 1 g/mol.

Calculation of molar mass

Molar mass is calculated as follows:

• determine the atomic masses of elements according to the periodic table;
• determine the number of atoms of each element in the compound formula;
• determine the molar mass by adding the atomic masses of the elements included in the compound, multiplied by their number.

For example, let's calculate the molar mass of acetic acid

It consists of:

• two carbon atoms
• four hydrogen atoms
• two oxygen atoms

• carbon C = 2 × 12.0107 g/mol = 24.0214 g/mol
• hydrogen H = 4 × 1.00794 g/mol = 4.03176 g/mol
• oxygen O = 2 × 15.9994 g/mol = 31.9988 g/mol
• molar mass = 24.0214 + 4.03176 + 31.9988 = 60.05196 g/mol

Our calculator performs exactly this calculation. You can enter the acetic acid formula into it and check what happens.

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