Ferric chloride- the average salt of ferric iron and hydrochloric acid. In appearance, this chemical raw material is a soft crystalline mass of a rusty-brownish-black color. Its boiling point is 319°C, melting point is 309°C. Ferric chloride is formed by heating iron with chlorine. It can also be obtained as a by-product in the production of titanium chloride TiCl4 and aluminum chloride AlCl3. Another way to obtain ferric chloride is hot chlorination or oxidation of the FeCl2 solution, followed by evaporation of the FeCl3 solution.
The scope of ferric chloride is quite wide. It is used as coagulant for water purification, as a catalyst in organic synthesis, as a mordant in the process of dyeing fabrics, as well as for the preparation of iron pigments and other iron salts. Another solution of ferric chloride is used for etching printed circuit boards.
Ferric chloride is widely used as a coagulant in the process of industrial and municipal wastewater treatment. Compared with other coagulants, in particular with aluminum sulfate, this chemical product has an important advantage - ferric chloride endowed with a high rate of deposition of various impurities. As a result of hydrolysis, ferric chloride forms a sparingly soluble iron hydroxide. In the process of its formation, various organic and inorganic impurities are captured, forming loose flakes, which are easily removed from the treated effluents. Such flakes, with a density of 1001–1100 g/l and a size of 0.5–3.0 mm, have a rather large surface with excellent sorption activity. In the process of their formation, the structure includes suspended substances (large microorganisms, plankton cells, silt, plant remains), colloidal particles, as well as part of the pollution ions associated on the surface of these particles. With the help of this product, the process of sedimentation of sludge proceeds much faster and deeper. Another advantage of ferric chloride is its beneficial effect on the biochemical decomposition of sludge. For high-quality wastewater treatment, 30 g of ferric chloride is required per cubic meter. Water purification with ferric chloride reduces the content of soluble impurities up to 25 percent, and insoluble impurities up to 95 percent. During the treatment of industrial and municipal wastewater, toxic compounds and microorganisms are destroyed by sodium hypochlorite.
Due to its pronounced acidic properties, iron chloride is used as a catalyst in organic synthesis processes, in the production of heat-resistant resins and in the oxidation of petroleum bitumen. Ferric chloride is an energetic chlorinating agent, so it is used for the selective extraction of certain components of ores. In particular, this chemical feedstock is required in aromatic hydrocarbons for the electrophilic substitution reaction. The use of aqueous solutions of ferric chloride is also well known. With fairly mild etching properties, they are used in the electronics and instrumentation industries for etching printed circuit boards, metal parts, and copper foil. Applies ferric chloride and in construction. It is used as an additive to Portland cement to speed up the setting process. The addition of ferric chloride significantly increases the strength of concrete. This product is also used in other areas of human life, in particular:
with its help, natural waters in water treatment systems are clarified;
oil is removed from the effluents of fat-and-oil plants;
it is used in the treatment of wastewater from leather and fur enterprises from chromium compounds;
to soften domestic and drinking water;
as well as in organochlorine synthesis
General information about the hydrolysis of iron (III) chloride
DEFINITION
Iron(III) chloride- an average salt formed by a weak base - iron (III) hydroxide (Fe (OH) 3) and a strong acid - hydrochloric (hydrochloric) (HCl). Formula - FeCl 3.
It is a substance with a crystalline structure of black-brown, dark red, purple or green, depending on the angle of the incident light. Molar mass - 162 g / mol.
Rice. 1. Iron (II) chloride. Appearance.
Hydrolysis of iron(III) chloride
Hydrolyzed at the cation. The nature of the medium is acidic. Theoretically, the second and third steps are possible. The hydrolysis equation looks like this:
First stage:
FeCl 3 ↔ Fe 3+ + 3Cl - (salt dissociation);
Fe 3+ + HOH ↔ FeOH 2+ + H + (cation hydrolysis);
Fe 3+ + 3Cl - + HOH ↔ FeOH 2+ + 3Cl - + H + (ionic equation);
FeCl 3 + H 2 O ↔ Fe(OH)Cl 2 + HCl (molecular equation).
Second step:
Fe(OH)Cl 2 ↔ FeOH 2+ + 2Cl - (salt dissociation);
FeOH 2+ + HOH ↔ Fe(OH) 2 + + H + (cation hydrolysis);
FeOH 2+ + 2Cl - + HOH ↔ Fe(OH) 2 + + 2Cl - + H + (ionic equation);
Fe(OH)Cl 2 + H 2 O ↔ Fe(OH) 2 Cl + HCl (molecular equation).
Third step:
Fe(OH) 2 Cl ↔ Fe(OH) 2 + + Cl - (salt dissociation);
Fe(OH) 2 + + HOH ↔ Fe(OH) 3 ↓ + H + (cation hydrolysis);
Fe(OH) 2 + + Cl - + HOH ↔ Fe(OH) 3 ↓ + Cl - + H + (ionic equation);
Fe(OH) 2 Cl + H 2 O ↔ Fe(OH) 3 ↓ + HCl (molecular equation).
Examples of problem solving
EXAMPLE 1
| Exercise | A solution of iron (III) chloride was added to a solution of sodium hydroxide weighing 150 g (ω = 10%), resulting in a brown precipitate - iron (III) hydroxide. Determine its mass. |
| Solution | We write the reaction equation for the interaction of sodium hydroxide and iron (III) chloride: 3NaOH + FeCl 3 \u003d Fe (OH) 3 ↓ + 3NaCl. Calculate the mass of the solute of sodium hydroxide in solution: ω = m solution / m solution ×100%; m solve = m solution ×ω/100%; m solute (NaOH) = m solution (NaOH) × ω(NaOH)/100%; msolute (NaOH) = 150 x 10/100% = 15g. Find the amount of sodium hydroxide substance (molar mass - 40 g / mol): υ (NaOH) \u003d m solute (NaOH) / M (NaOH) \u003d 15/40 \u003d 0.375 mol. According to the reaction equation υ (Fe (OH) 3) \u003d 3 × υ (NaOH) \u003d 3 × 0.375 \u003d 1.125 mol. Then we calculate the mass of the iron (III) hydroxide precipitate (molar mass - 107 g / mol): m (Fe (OH) 3) \u003d υ (Fe (OH) 3) × M (Fe (OH) 3) \u003d 1.125 × 107 \u003d 120.375 g. |
| Answer | The mass of iron (III) hydroxide is 120.375 g. |
EXAMPLE 2
| Exercise | Calculate the mass fractions of each of the elements that make up iron (III) chloride. |
| Solution | The mass fraction of an element is calculated as follows: ω(X) = n×Ar(X)/Mr×100%, those. the ratio of the relative atomic mass, taking into account the number of atoms that make up the substance, to the molecular weight of this substance, expressed as a percentage. The molecular weight of iron (III) chloride is 162. Calculate the mass fractions of elements: iron : ω (Fe) \u003d n × Ar (Fe) / Mr (FeCl 3) × 100%; ω(Fe) = 1×56/162×100% = 34.27%. chlorine: ω(Cl) \u003d n × Ar (Cl) / Mr (FeCl 3) × 100%; ω(Cl) = 3×35.5/162×100% = 65.73%. To check the correctness of the calculation, by adding the mass fractions obtained, we must get 100%: ω(Fe) + ω(Cl) = 34.27 + 65.73 = 100%. |
| Answer | The mass fraction of iron is 34.27%, the mass fraction of chlorine is 65.73. |
Ferric chloride (III) in the form of a solution can be prepared in the laboratory or at home. You will need heat-resistant non-metallic utensils and clean hot or distilled). After dissolution and settling, a dark brown liquid is obtained. There are a number of features in the preparation of a ferric chloride solution that you should learn about before you start working with it.
Ferric chloride
Anhydrous ferric chloride, produced by the chemical industry - FeCl 3 - dark brown crystals with shades of red, purple, dark green. Molar mass - 162.21 g / mol. The substance melts at a temperature of 307.5 ° C, at 500 ° C it begins to decompose. A sample of anhydrous salt dissolves in 100 g of water:
- 74.4 g (0°C);
- 99 g (25 °C);
- 315 g (50 °C);
- 536 g (100 °C).
Anhydrous (III) - a very hygroscopic substance, quickly attracts moisture from the environment. In air, it interacts with water, turning into yellow crystals of FeCl 3 + 6H 2 O hexahydrate. The mass fraction of anhydrous ferric chloride in a substance purchased in a commercial network reaches 95%. There is a small amount of ferric chloride FeCl 2 and insoluble impurities. The trade name is Ferric Chloride. The substance is fire and explosion-proof, but its solution has a corrosive effect on metal objects.
Iron(III) chloride hexahydrate
In addition to anhydrous, the industry produces crystalline hydrate, in which the mass fraction of ferric chloride (III) is 60%. The substance is a yellow-brown crystalline mass or loose pieces of the same shade. An important distinguishing feature of ferrous and ferric ions is color. The oxidation state of Fe 2+ is characterized by a greenish tint, the hexahydrate iron chloride hydrate is a bluish-green substance. In the oxidation state of Fe 3+ ions acquire a color from yellow to brown. For a qualitative determination, reagents act on a solution of ferric chloride:
- NaOH (a brown precipitate of Fe (OH) 3 appears);
- K 4 (a blue precipitate of KFe appears);
- KCNS, NaCNS (iron thiocyanate Fe(CNS) 3 red is formed).
How to dilute ferric chloride
Iron (III) chloride in the form of a brown or red solution can be found in the commercial network, prepared in the laboratory or at home. In the latter case, you will definitely need heat-resistant non-metallic dishes (glass, plastic, ceramic). Water for dissolving salt can be taken from the tap. Safer - boiled or distilled. Water heated to 50-70 ° C is placed in a container, and then the substance is poured in small portions. The proportions of ferric chloride and water are 1:3. If you prepare a solution from crystalline hydrate, then less water will be required, because it is contained in crystalline hydrate (40% by weight). The substance is added to the solution little by little, each portion is about 5-10 g. It is not recommended to immediately pour the entire sample due to the rapid nature of the hydration reaction. Do not use metal utensils (spoons, spatulas). Salt must be completely dissolved in warm water, for which the crystals must be mixed well with the liquid. The process is accelerated by the addition of hydrochloric acid (1/10 of the mass of the crystals). After settling for several hours, a precipitate may appear at the bottom due to the presence in the sample and the formation of iron hydroxide during the reaction. The prepared dark brown solution should be filtered and stored in a tightly closed plastic container at a moderate temperature and out of direct sunlight.
The use of ferric chloride in industry and public utilities. domestic use
Iron salts find applications in many fields. Trivalent metal chloride is used for water treatment, metals and paint fixing. The substance is used in industrial organic synthesis (catalyst, oxidizer). The coagulating properties of the Fe 3+ ion are especially valued in the treatment of municipal and industrial wastewater. Under the action of ferric chloride, small insoluble particles of impurities stick together and precipitate. Also, there is a binding of a part of soluble contaminants, which are removed at the treatment plant. Crystal hydrate and anhydrous salt FeCl 3 are used in the etching of metal printing plates. A substance is added to concrete to strengthen its strength.
Chemical phenomena during etching of boards. Security measures
A popular chemical for PCB etching is ferric chloride. A solution for these purposes is prepared from 0.150 kg of salt and 0.200 l of warm water. It contains Fe 3+, Cl - ions, and upon hydrolysis, a brown compound is formed - ferric hydroxide. The process goes according to the scheme: FeCl 3 + 3HOH ↔ Fe (OH) 3 + 3Cl - + 3H +. The disadvantage of this method is the contamination of the board with reaction by-products, which make further etching difficult. Salt itself is a non-volatile substance, but in the process of interaction with water it releases caustic fumes. Work must be carried out outdoors or in a well-ventilated room. Contact with the solution on the skin and mucous membranes leads to irritation and can cause dermatitis. Personal protective equipment (goggles, gloves) should be used. In case of contact with a caustic solution, wash the skin with plenty of water.
SECTION II. INORGANIC CHEMISTRY
8.
Metal elements and their compounds. Metals
8.5. Ferum
8.5.2. Iron Compounds ( III)
Ferum(III) oxide Fe 2 O 3 - the most stable natural iron spore, brown powder, has atomic crystal lattices, does not dissolve in water. Ferum (III) oxide exhibits weak amphoteric properties (with a predominance of basic ones) - it easily reacts with acids:
Shows weak acidic properties of the alloy with alkalis and carbonates of alkali metal elements:
Sodium ferrite formed in an aqueous solution is completely decomposed by water (hydrolyzes):
Reducing agents reduce iron(III) oxide to iron:
Ferrum(III) oxide production Ferrum(III) oxide is obtained by thermal decomposition of ferum(III) hydroxide or ferrum(III) nitrate:
It is also obtained during pyrite roasting. FeS 2 :
Ferrum(III) hydroxide Fe (OH) 3 1 - a water-insoluble brown substance with weak amphoteric properties (with a predominance of basic ones):
Reactions with concentrated alkali solutions proceed only with prolonged heating. This forms a stable hydroxocomplex K 3 [Fe(OH) 6]:
Extraction of ferrum(III) hydroxide
Ferrum (III) hydroxide is obtained from water-soluble salts of Iron (III) when they interact with alkalis:
Iron(III) salts formed by strong acids are highly soluble in water and can form crystalline hydrates: Fe (N O 3) 3 9H 2 O, Fe 2 (S O 4) 3 9H 2 O, FeCl 3 6H 2 O. Fe 3+ salts hydrolyze at the cation:
Iron(III) compounds exhibit oxidizing properties, and therefore, when interacting with reducing agents Fe 3+ turns into Fe 2+:
Qualitative reactions to an ion Fe3+ :
1. Reagent - potassium hexacyanoferate (II) (yellow blood salt). A dark blue precipitate is formed - Prussian blue:
2. Reagent - potassium (or ammonium) thiocyanate. Ferrum(III) thiocyanate of blood-red color is formed:
Use of Iron and Iron Compounds
Ferrous metallurgy (the production of iron and its alloys) accounts for 90% of the world's metallurgy. Ferrous metallurgy is the basis for the development of many industries: mechanical engineering uses a third of ferrous metal, construction (as a structural material, for the manufacture of reinforced concrete) - a quarter; a significant part is also used in transport.
Iron-based alloys (ferromagnetic) are used in electrical engineering in the production of transformers and electric motors.
Ferum(II) oxide FeO is one of the components of ceramics, pigment for paints and heat-resistant enamel.
Ferum(III) oxide Fe 2 O 3 ocher is used as a mineral paint.
Magnetite Fe 3 O 4 used in the manufacture of hard drives, and ultrafine powder - as a toner in black and white laser printers.
Ferrous vitriol (iron(II) sulfate heptahydrate) FeS В 4 7H 2 O is used to control plant pests, in the production of mineral paints, and in construction.
Ferrum(III) chloride is used for water purification, as a mordant for dyeing fabrics, in radio engineering for etching printed circuit boards, and in organic synthesis as a catalyst.
Aqueous solutions of FeCl 2 , FeCl 3 , FeS B 4 are used as coagulants to purify water for industrial plants.
Ferrum(III) nitrate nonahydrate Fe (N O 3 ) 3 9H 2 V is used as a mordant in the process of dyeing fabrics.
1 As in the case of Fe 3 O 4 , substances with the formula Fe(OH ) 3 does not exist. When you try to get it, it generates Fe 2 O 3 n H 2 O or FeO (OH ) - ferrum(III) metahydroxide.
Ferric chloride (FeCl₃, ferric chloride, iron trichloride) is a ferric salt and. It is a soft substance of a red-brown, greenish or purple hue with a characteristic metallic sheen. When exposed to air, iron chloride acquires a hue and, in color and consistency, becomes similar to wet.
A number of properties that ferric chloride has due to its chemical composition make this substance indispensable in industry. So, ferric chloride is used in radio electronics to damage circuit boards; participates in the food industry in the process of brewing and baking bakery products; is part of the reagents that are used when printing photographs; in the textile industry involved in the production of fabrics; with the help of ferric chloride, they purify water on an industrial scale; Ferric chloride is an important element in the metallurgical and chemical industries.
In addition, ferric chloride is necessary for a person for the normal functioning of the body. It helps the body to compensate for the lack of iron associated with blood loss or in violation of the absorption of iron. Since the lack of ferric chloride can adversely affect the functioning of the body, in pharmacology there are many drugs that include FeCl₃.
How to get
There are several ways to obtain iron trichloride. So, iron chloride as a result of the interaction of monovalent iron with pure chlorine: 2Fe + 3Cl2 = FeCl₃.
In addition, iron chloride can be obtained by oxidizing ferrous chloride with chlorine: 2FeCl2 + Cl2 = 2FeCl₃.
Iron chloride is also obtained in the process of oxidation of iron (II) chloride with sulfur dioxide. In this case, a more complex chemical reaction occurs: 4FeCl2 + SO2 + 4HCl = 4FeCl3 + S + 2H2O.
At home, you can conduct some interesting experiments, during which it will be possible to obtain ferric chloride.
Experiment 1
You will need heavily rusted iron shavings (ordinary rust from an old pipe will do) and a solution of hydrochloric acid in proportions of 1: 3. Iron must be put in a glass container and filled with hydrochloric acid. Since the chemical reaction in this case proceeds rather slowly, you will have to wait a few days. When the reagent acquires a characteristic yellow-brown tint, the liquid is drained from the container, and the resulting precipitate is filtered.Experiment 2
In a glass container in proportions 2:2:6, mix a 30% solution of hydrogen peroxide, hydrochloric acid and water. As a result of a chemical reaction, a solution of ferric chloride is formed.Experiment 3
Iron chloride can also be obtained by the reaction of hydrochloric acid and iron oxide Fe2O3. For this, hydrochloric acid is placed in a glass container. Carefully, iron oxide (iron minium) is added to it in small portions.It is important to remember that hydrochloric acid is very toxic and causes severe burns if it comes into contact with the skin. In addition, during chemical reactions, iron vapors are released, which can cause damage to the respiratory and visual organs. Rubber gloves, a protective mask and goggles will help prevent these negative consequences.
