Sodium- element of the 3rd period and IA group Periodic table, serial number 11. Electronic formula of the atom is 3s 1, oxidation states +1 and 0. It has low electronegativity (0.93), exhibits only metallic (basic) properties. Forms (as a cation) numerous salts and binary compounds. Almost all sodium salts are highly soluble in water.
In nature - fifth by chemical abundance element (second among
metals), found only in the form of compounds. A vital element for all organisms.
Sodium, sodium cation and its compounds color the gas burner flame bright yellow ( qualitative detection).
Sodium Na. Silver-white metal, light, soft (can be cut with a knife), low-melting. Store sodium in kerosene. Forms a liquid alloy with mercury - amalgam(up to 0.2% Na).
Very reactive, in humid air sodium slowly becomes covered with a hydroxide film and loses its luster (tarnishes):
Sodium is chemically active and a strong reducing agent. Ignites in air at moderate heating (>250 °C), reacts with non-metals:
2Na + O2 = Na2O2 2Na + H2 = 2NaH
2Na + CI2 = 2NaCl 2Na + S = Na2S
6Na + N2 = 2Na3N 2Na + 2C = Na2C2
Very stormy and with great exo-effect sodium reacts with water:
2Na + 2H2O = 2NaOH + H2^ + 368 kJ
From the heat of the reaction, the sodium pieces melt into balls, which begin to move randomly due to the release of H 2. The reaction is accompanied by sharp clicks due to explosions of detonating gas (H 2 + O 2). The solution is colored crimson with phenolphthalein (alkaline medium).
In the voltage series, sodium is significantly to the left of hydrogen; it displaces hydrogen from dilute acids HC1 and H 2 SO 4 (due to H 2 0 and H).
Receipt sodium in industry:
(see also NaOH preparation below).
Sodium is used to produce Na 2 O 2, NaOH, NaH, as well as in organic synthesis. Molten sodium serves as a coolant in nuclear reactors, and gaseous - is used as a filler for yellow-light outdoor lighting lamps.
Sodium oxide Na 2 O. Basic oxide. White, has an ionic structure (Na +) 2 O 2-. Thermally stable, decomposes slowly when heated, melts under excess Na vapor pressure. Sensitive to moisture and carbon dioxide in the air. Reacts vigorously with water (a strongly alkaline solution is formed), acids, acidic and amphoteric oxides, oxygen (under pressure). Used for the synthesis of sodium salts. Not formed when sodium is burned in air.
Equations of the most important reactions:
Receipt: thermal decomposition of Na 2 O 2 (see), as well as fusion of Na and NaOH, Na and Na2O2:
2Na + 2NaOH = 2Na a O + H2 (600 °C)
2Na + Na2O2 = 2Na and O (130-200 °C)
Sodium peroxide Na 2 O 2 . Binary connection. White, hygroscopic. It has an ionic structure (Na +) 2 O 2 2-. When heated, it decomposes and melts under excess pressure O 2 . Absorbs carbon dioxide from the air. Completely decomposes with water and acids (release of O2 during boiling - qualitative reaction to peroxides). Strong oxidizing agent, weak reducing agent. It is used for oxygen regeneration in self-contained breathing devices (reaction with CO 2), as a component of fabric and paper bleaches. Equations of the most important reactions:
Receipt: combustion of Na in air.
Sodium hydroxide NaOH. Basic hydroxide, alkali, technical name is caustic soda. White crystals with ionic structure (Na +)(OH -). It dissolves in air, absorbing moisture and carbon dioxide (NaHCO 3 is formed). Melts and boils without decomposition. Causes severe burns to skin and eyes.
Very soluble in water (with exo-effect, +56 kJ). Reacts with acid oxides, neutralizes acids, causes acid function in amphoteric oxides and hydroxides:
The NaOH solution corrodes glass (NaSiO3 is formed) and corrodes the aluminum surface (Na and H2 are formed).
Receipt NaOH in industry:
a) electrolysis of NaCl solution on an inert cathode
b) electrolysis of NaCl solution on a mercury cathode (amalgam method):
(the released mercury is returned to the electrolyzer).
Caustic soda is the most important raw material of the chemical industry. Used to produce sodium salts, cellulose, soap, dyes and artificial fibers; as a gas dryer; reagent in recovery from secondary raw materials and purification of tin and zinc; when processing aluminum ores (bauxite).
You will need sodium Na and potassium K, distilled water, an alcohol solution of phenolphthalein indicator, crystallizers, tweezers or forceps, a scalpel or sharp knife, and filter paper.
Water is poured into the crystallizers and a few drops of phenolphthalein solution are added. Using a scalpel, cut small, pea-sized “slices” from pieces of alkali metals on a sheet of filter paper. Pieces of sodium and potassium are dried with filter paper and placed in crystallizers. Before taking another piece of metal, carefully wipe the ends of the tweezers with filter paper so as not to introduce water into the bottles. Balls of molten metal are observed “running” along the surface of the water, and the movement of the potassium ball is more rapid than that of the sodium one. It soon lights up with a purple flame. Behind each of the “running” balls there is a crimson “trail” due to the fact that as a result of the reactions:
2Na + 2H 2 O = 2NaOH + H 2
2K + 2H 2 O = 2KOH + H 2
an alkaline hydroxide (strong base) is formed, which colors the phenolphthalein indicator crimson-violet.
Hardware and the objects are cleaned of dirt, degreased with a soda solution, washed in water, immersed in a 50% nitric acid solution for a few seconds and washed again with distilled water. The prepared product is kept for 30-50 minutes in a hot solution containing 280 g of nickel sulfate heptahydrate and 100 ml of concentrated hydrochloric acid per 1 liter of water. After receiving the nickel coating (it turns out dense and shiny), the product is washed with water and polished with cloth.
Copper crystals
Everyone knows how to grow crystals various salts. But not everyone can grow copper crystals. For this unusual experiment you will need: CuSO4, table salt, a piece of tin and a glass (or an ordinary one). Cut a circle from a piece of tin so that it fits freely into the glass. Pour copper sulfate powder (copper sulfate) into a glass in a 5 mm layer and cover this layer with salt. ATTENTION! Do not mix the layers. Cover the layers with a circle of filter paper and cover with a circle of tin. Pour the salt solution into a glass.
After two weeks, fairly large copper crystals will grow. To keep them well preserved, place them in a test tube with a solution of sulfuric acid.
Combustion of metals.
The combustion of metals in oxygen and chlorine is widely known. Less familiar is the combustion of metals in sulfur vapor. A large test tube filled one-third with sulfur is placed vertically in a stand and heated until the sulfur boils. Then a bundle of thin copper wire (can be preheated) is lowered into the test tube and a violent reaction is observed.
Sodium combustion.
A piece of filter paper, generously moistened with water, is placed on the asbestos mesh. Then a piece of sodium is placed on the paper. Sodium reacts with water, due to the released energy it melts, spontaneously ignites and burns with a bright yellow flame. The combustion reaction involves both the released hydrogen and the filter paper.
Nickel plating of metal objects.
Metal products and objects are cleaned of dirt, degreased with a soda solution, washed in water, dipped in a 50% nitric acid solution for a few seconds and washed again with distilled water. The prepared product is kept for 30-50 minutes in a hot solution containing 280 g of nickel sulfate heptahydrate and 100 ml of concentrated hydrochloric acid per 1 liter of water. After receiving the nickel coating (it turns out dense and shiny), the product is washed with water and polished with cloth.)
Silvering of copper objects.
Copper objects and products are thoroughly cleaned of dirt, washed with a soda solution and dipped in a used fixer solution for several days. After receiving the silver coating, the product is washed with water and polished with a cloth.
Sodium is a very reactive metal that reacts with many substances. Reactions involving sodium can occur violently and produce significant heat. In this case, ignition and even an explosion often occur. To work safely with sodium, it is necessary to have a clear understanding of its physical and chemical properties.
Sodium is a light (density 0.97 g/cm3), soft and fusible (melt 97.86° C) metal. Its hardness resembles paraffin or soap. In air, sodium oxidizes very quickly, becoming covered with a gray film, which consists of Na2O2 peroxide and carbonate, so sodium is stored in well-closed jars under a layer of anhydrous kerosene or oil.
A piece of sodium of the required size is cut off without removing the metal from the kerosene, using a knife or scalpel. Sodium is removed from the jar with tweezers. All tools must be dry! After this, sodium is freed from kerosene residues using filter paper. In some cases, the metal is cleaned with a scalpel to remove the peroxide layer, since contact of peroxide with fresh sodium surface can lead to an explosion. Sodium should not be handled by hand. Sodium scraps are fused with low heat under a layer of kerosene.
Under no circumstances should dishes that contain sodium be washed with water - this can lead to an explosion with tragic consequences. Residues of sodium are eliminated by adding alcohol, only then can water be used.
It is necessary to wear safety glasses when working with sodium. Never forget what you are dealing with - an explosion can happen at the most unexpected and inopportune moment, and you need to be prepared for this.
Reaction of sodium with water
Fill the crystallizer 3/4 full with water and add a few drops of phenolphthalein to it. Drop a half-pea-sized piece of sodium into the crystallizer. The sodium will remain on the surface because it is lighter than water. The piece will begin to actively react with water, releasing hydrogen. From the heat of the reaction, the metal will melt and turn into a silvery droplet that will actively run along the surface of the water. At the same time, a hissing sound is heard. Sometimes the hydrogen that is released lights up with a yellow flame. Sodium vapor gives it this color. If ignition does not occur, the hydrogen can be ignited. However, pieces of sodium smaller than a grain of wheat are extinguished.
As a result of the reaction, an alkali is formed, which acts on phenolphthalein, so a piece of sodium leaves behind a raspberry trail. At the end of the experiment, almost all the water in the crystallizer will turn crimson.
2Na + 2H2O = 2NaOH + H2
The walls of the crystallizer must be free of grease and other contaminants. If necessary, they are washed with an alkali solution, otherwise sodium sticks to the walls and the crystallizer may crack.
The experiment should be carried out wearing a protective mask or safety glasses. During the reaction, keep a certain distance and do not lean over the crystallizer under any circumstances. Getting molten sodium or alkali splashes into your eyes can lead to virtually guaranteed blindness.
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