In the modern world, life is impossible without chemical reactions that occur everywhere and are both useful and dangerous. According to the periodic table of chemical elements of D. I. Mendeleev, metals of the first group of the main subgroup, including sodium (Na), react violently with water, forming alkalis - chemically active substances.
The concept of alkalis
Water-soluble hydroxides of active metals - alkalis - are caustic and rather dangerous chemicals. In their form they are solid, white. Dissolving in water, these bases give off heat. Also, alkalis are capable of destroying skin, wood, and tissues, as a result of which they have received the trivial name "caustic", which is usually applied only to alkali metal hydroxides. The most famous alkalis include hydroxides of sodium (NaOH), potassium (KOH), lithium (LiOH), barium (Ba (OH) 2 ), cesium (CsOH), calcium (Ca (OH) 2 ) and some others.
Sodium hydroxide: characteristic
Caustic soda is the trivial name for sodium hydroxide - one of the most common alkalis. It refers to hazardous chemicals, because it easily corrodes human skin, so you need to follow the necessary safety measures when working with it. Also, sodium hydroxide is sometimes called caustic soda, or caustic. Like all other alkalis, it interacts well with water with heat and is white, hygroscopic, that is, a compound capable of absorbing water vapor from air. The density of caustic soda is 2.13 g / cm³.
Reactivity
A solution of caustic soda can enter into reactions of various types, forming other substances.
1. When this compound reacts with acids, salt and water always form:
NaOH + HCl = NaCl 2 + H 2 O.
2. Caustic soda is able to react with acidic and amphoteric metal oxides (in solution and during fusion), also forming the corresponding salt and water:
- 2NaOH + SO 3 = Na 2 SO 4 + H 2 O (SO 3 - acid oxide);
- 2NaOH + ZnO = Na 2 ZnO 2 + H 2 O (ZnO is an amphoteric oxide, this reaction takes place during fusion and heating).
The interaction of sodium hydroxide with a solution of amphoteric oxide forms a soluble complex salt.
3. The reaction of alkali with amphoteric hydroxides also leads to the formation of a melt or complex sodium salt, depending on the conditions of its implementation.
4. By the interaction of caustic with salts, sodium and the corresponding water-insoluble hydroxide are obtained.
- 2NaOH + MgCl 2 = 2NaCl + Mg (OH) 2 (magnesium hydroxide is a water-insoluble base).
5. Sodium hydroxide is able to react with non-metals, for example sulfur or halogens with the formation of a mixture of sodium salts, as well as amphoteric metals with the formation of complex salts, iron and copper.
- 3S + 6NaOH = 2Na 2 S + Na 2 SO 4 + 3H 2 O.
6. Caustic soda is able to interact with organic substances, for example: esters, amides, polyhydric alcohols.
- 2C 2 H 6 O 2 + 2NaOH = C 2 H 4 O 2 Na 2 + 2H 2 O (the reaction product is sodium alcoholate).
Getting
There are several methods for producing caustic soda in industry, the main of which are chemical and electrochemical.
The first method is based on several methods: pyrolysis, calcareous and ferritic.
1. Pyrolysis is carried out by calcining sodium carbonate at high temperature (not less than 1000 degrees) with the formation of sodium oxide and carbon dioxide. Next, the obtained cooled oxide is dissolved in water, resulting in caustic soda.
- Na 2 CO 3 = Na 2 O + CO 2 (at 1000 degrees);
- Na 2 O + H 2 O = 2 NaOH.
Sometimes, instead of sodium carbonate, its hydrocarbonate is used, and the process, accordingly, is a little more complicated.
2. The calcareous method for producing sodium hydroxide consists in the interaction of the sodium salt of carbonic acid with calcium hydroxide (hydrated lime) when heated to a temperature of at least 80 degrees. As a result of this interaction, solutions of alkali and calcium carbonate (CaCO 3 ) are obtained, which is then filtered off from the main solution.
- Na 2 CO 3 + Ca (OH) 2 = 2NaOH + CaCO 3.
3. The ferrite method is carried out in two stages: first, the soda is fused with iron oxide III at a temperature of up to 1200 degrees to obtain sodium ferrite, then the latter is treated with water, resulting in alkali.
- Na 2 CO 3 + Fe 2 O 3 = 2NaFeO 2 + CO 2;
- 2NaFeO 2 + 2H 2 O = 2NaOH + Fe 2 O3 * H 2 O.
In the electrochemical method of producing caustic soda, several methods are also used: electrolysis of a solution of sodium chloride (NaCl), diaphragm, membrane and mercury methods with a liquid cathode. The last three methods are more complicated compared to the first, but all of them are associated with passing the corresponding salts of electric current through the solution, that is, with electrolysis.
The most common method for producing alkali is the electrolysis of a halite solution consisting of sodium chloride, as a result of which chlorine and hydrogen are released at the anode and cathode, and sodium hydroxide is obtained:
- 2NaCl + 2H 2 O = H 2 + Cl 2 + 2NaOH.
In the laboratory, caustic soda is also obtained by chemical methods, but the most commonly used diaphragm and membrane methods.
Application
Caustic soda is used not only in various industries, but also in everyday life. It is used:
- By production of detergents.
- To neutralize acids or as a catalyst in chemical industries.
- For the preparation of biodiesel, which is more environmentally friendly than conventional diesel.
- Dry granules are made from it, with the help of which sewer pipes and sinks are cleaned of food clogs.
- Caustic soda is also applicable in the manufacture of food products, such as bread or cocoa. It is used as a food supplement.
- In cosmetology, the substance is used to remove dead skin.
- For faster photo processing.
- Technical caustic soda is widely used in the chemical, petrochemical, oil refining, pulp and paper, mining, textile, food and many other industries.
Precautionary measures
Caustic soda is a strong base. It can easily damage not only tissue, but also human skin, which will be accompanied by burns. When working with this substance, certain safety measures must be observed, namely:
- It is necessary to wear special rubber gloves, glasses to prevent the solution from getting into hands and eyes.
- You need to wear clothes that are resistant to chemical compounds and will not allow them to get on the skin of the body. Typically, such clothing is treated with polyvinyl chloride.