The interaction of sodium with water is formed. Secrets of the reaction of metallic sodium with water. Nickel plating of metal objects

The most interesting on school lessons chemistry was the topic of the properties of active metals. We were not only presented with theoretical material, but also demonstrated interesting experiments. Probably everyone remembers how the teacher threw a small piece of metal into the water, and it rushed over the surface of the liquid and ignited. In this article, we will understand how the reaction of sodium and water occurs, why the metal explodes.

Metallic sodium is a silvery substance that resembles soap or paraffin in density. Sodium is characterized by good thermal and electrical conductivity. That is why it is used in industry, in particular for the manufacture of batteries.

Sodium is highly reactive. Reactions often take place with the release of a large amount of heat. Sometimes this is accompanied by fire or explosion. Working with active metals requires good informational training and experience. Sodium can only be stored in well-closed containers under a layer of oil, since the metal is rapidly oxidized in air.

Sodium's most popular reaction is to react with water. During the reaction sodium plus water, alkali and hydrogen are formed:

2Na + 2H2O = 2NaOH + H2

Hydrogen is oxidized by oxygen from the air and explodes, which we observed during the school experiment.

Reaction studies by scientists from the Czech Republic

The reaction of sodium with water is very simple to understand: the interaction of substances leads to the formation of H2 gas, which, in turn, is oxidized by the O2 in the air and ignites. Everything seems to be simple. But Professor Pavel Jungvirt from the Czech Academy of Sciences did not think so.

The fact is that during the reaction, not only hydrogen is formed, but also water vapor, since a large amount of energy is released, the water heats up and evaporates. Since sodium has a low density, the steam cushion must push it upward, isolating it from the water. The reaction should fade, but it doesn't.

Jungwirth decided to study this process in detail and filmed the experiment with a high-speed camera. The process was filmed at a speed of 10 thousand frames per second and viewed with a 400-fold slowdown. Scientists have noticed that the metal, getting into the liquid, begins to release processes in the form of thorns. This is explained as follows:

• Once in water, alkali metals begin to act as an electron donor and donate negatively charged particles.
• A piece of metal takes on a positive charge.
• The positively charged protons begin to repel each other, forming metal offshoots.
• The spikes pierce the vapor pad, the contact surface of the reactants increases, and the reaction intensifies.

How to experiment

In addition to hydrogen, alkali is formed during the reaction of water and sodium. To check this, you can use any indicator: litmus, phenolphthalein, or methyl orange. It will be easiest to work with phenolphthalein, since it is colorless in a neutral environment and the reaction will be easier to observe.

To conduct an experiment you need:

1. Pour distilled water into the crystallizer so that it occupies more than half of the vessel's volume.
2. Add a few drops of indicator to the liquid.
3. Cut off a piece of sodium, the size of half a pea. To do this, use a scalpel or thin knife. You need to cut the metal in a container, not blaming sodium from the oil, in order to avoid oxidation.
4. Remove a piece of sodium from the jar with tweezers and blot with filter paper to remove oil.
5. Throw sodium into water and observe the process from a safe distance.

All instruments used in the experiment must be clean and dry.

You will see that sodium is not immersed in water, but remains on the surface, due to the density of the substances. The sodium will begin to react with the water, generating heat. This will melt the metal and turn into a droplet. This droplet will begin to actively move through the water, emitting a characteristic hiss. If the sodium lump was not too small, it will light up with a yellow flame. If the piece was too large, an explosion could occur.

Also, the water will change its color. This is due to the release of alkali into the water and the color of the indicator dissolved in it. Phenolphthalein turns pink, litmus blue, and methyl orange turns yellow.

this is dangerous

The interaction of sodium with water is very dangerous. During the experiment, you can get serious injuries. Hydroxide, peroxide and sodium oxide that form during the reaction can corrode the skin. Splashing alkali can get into the eyes and cause severe burns and even blindness.

Manipulations with active metals should be carried out in chemical laboratories under the supervision of a laboratory assistant who has experience in working with alkali metals.

1. Wear protective goggles only.
2. Never lean over the vessel when the metal is in the water.
3. Move away from the crystallizer a few meters immediately after the metal is thrown into the water.
4. Always be ready, as an explosion can occur at any moment.
5. Do not approach the catalyst until you are sure that the reaction is complete.

Sodium Metallic Properties: Video

Sodium- element of the 3rd period and IA-group Periodic table, serial number 11. Electronic formula atom 3s 1, oxidation states +1 and 0. Has low electronegativity (0.93), exhibits only metallic (basic) properties. Forms (as a cation) numerous salts and binary compounds. Almost all sodium salts are readily soluble in water.

In nature - fifth in terms of chemical abundance, an element (second among
metals), is found only in the form of compounds. A vital element for all organisms.

Sodium, sodium cation and its compounds color the flame of a gas burner bright yellow ( quality detection).

Sodium Na. Silver-white metal, light, soft (cut with a knife), low melting point. 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 (fades):

Sodium is chemically active, a strong reducing agent. Flammable 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 a lot exo-the effect of sodium reacts with water:

2Na + 2H2O = 2NaOH + H2 ^ + 368 kJ

The heat of reaction melts the sodium pieces 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 oxyhydrogen gas (H 2 + O 2). The solution is stained with phenolphthalein in a crimson color (alkaline medium).

In the series of voltages, sodium is much more to the left of hydrogen; from dilute acids HCl and H 2 SO 4 it displaces hydrogen (due to H 2 0 and H).

Receiving sodium in industry:

(see also the preparation of NaOH below).

Sodium is used to obtain Na 2 O 2, NaOH, NaH, as well as in organic synthesis. Molten sodium serves as a coolant in nuclear reactors, and gaseous sodium is used as a filler for yellow-light outdoor lamps.

Sodium oxide Na 2 O. Basic oxide. White, has an ionic structure (Na +) 2 O 2-. It is thermally stable, slowly decomposes when calcined, melts under excess pressure of Na vapor. Sensitive to moisture and carbon dioxide in the air. Reacts vigorously with water (a highly alkaline solution is formed), acids, acidic and amphoteric oxides, oxygen (under pressure). It is used for the synthesis of sodium salts. Does not form when sodium is burned in air.

Equations of the most important reactions:

Receiving: thermal decomposition of Na 2 O 2 (see), as well as fusion of Na and NaOH, Na and Na2O2:

2Na + 2NaOH = 2Na and O + H2 (600 ° C)

2Na + Na2O2 = 2Na a O (130-200 ° C)

Sodium peroxide Na 2 O 2. Binary connection... White, hygroscopic. Has an ionic structure (Na +) 2 O 2 2-. When heated, it decomposes, melts under excess pressure of O 2. Absorbs carbon dioxide from the air. Completely decomposes with water, acids (release of О 2 during boiling - qualitative reaction to peroxides). Strong oxidizing agent, weak reducing agent. It is used for oxygen regeneration in self-contained breathing apparatus (reaction with CO 2), as a component of fabric and paper bleaches. Equations of the most important reactions:

Receiving: combustion of Na in air.

Sodium hydroxide NaOH. Basic hydroxide, alkali, technical name caustic soda. White crystals with ionic structure (Na +) (OH -). It spreads out in the air, absorbing moisture and carbon dioxide (NaHCO 3 is formed). Melts and boils without decomposition. Causes severe burns to skin and eyes.

Let's well dissolve in water (with exo-effect, +56 kJ). Reacts with acid oxides, neutralizes acids, induces acid function in amphoteric oxides and hydroxides:

The NaOH solution corrodes glass (NaSiO3 is formed), corrodes the aluminum surface (Na and H 2 are formed).

Receiving 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 for the chemical industry. It is used to obtain sodium salts, cellulose, soaps, dyes and artificial fibers; as a gas dehumidifier; reagent in the 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 alcoholic solution of a phenolphthalein indicator, crystallizers, tweezers or forceps, a scalpel or sharp knife, and filter paper.

Water is poured into crystallizers and a few drops of phenolphthalein solution are added. Cut off small pieces of alkali metals with a scalpel on a sheet of filter paper, the size of a pea, "slices". Pieces of sodium and potassium are dried with filter paper and immersed in crystallizers. Before taking another piece of metal, carefully wipe the ends of the tweezers with filter paper so as not to bring water into the bottles. Balls of molten metal "running" on the surface of the water are observed, and the movement of the potassium ball is more rapid than that of the sodium one. It soon lights up with a violet 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 stains the phenolphthalein indicator in a raspberry-purple color.

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 a nickel coating (it turns out to be dense and shiny), the product is washed with water and polished with a cloth.

Copper crystals

Everyone knows how to grow crystals of various salts. But not everyone will be able to grow copper crystals. For this unusual experience you will need: CuSO4, salt, a piece of tin and a glass (you can ordinary). Cut a circle out of a piece of tin so that it fits freely into the glass. Pour copper sulfate (copper sulfate) powder into a glass in a layer of 5 mm and fill this layer with salt. ATTENTION! Do not mix the layers. Cover the layers with a filter paper circle and cover with a tin circle. Pour the salt solution into a glass.

Quite large copper crystals will grow in two weeks. To keep them well, place them in a test tube with sulfuric acid solution.

Combustion of metals.

Combustion of metals in oxygen, chlorine is widely known. Less familiar is the burning of metals in sulfur vapor. A large test tube, one-third full of sulfur, is placed vertically in a rack and heated until the sulfur boils. Then a bundle of thin copper wire is lowered into the test tube (you can preheat it) and a violent reaction is observed.

Combustion of sodium.

A piece of filter paper, abundantly moistened with water, is placed on the asbestos mesh. Then put a piece of sodium on the paper. Sodium reacts with water, due to the released energy it melts, self-ignites and burns with a bright yellow flame. The released hydrogen and filter paper are also included in the combustion reaction.

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% solution of nitric acid 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 a nickel coating (it turns out to be dense and shiny), the product is washed with water and polished with a cloth.)

Silver plating of copper objects.

Copper objects and products are thoroughly cleaned of dirt, washed with a soda solution and dipped for several days in a spent fixer solution. After receiving the silver coating, the product is washed with water and polished with a cloth cloth.