What is caustic soda? Density of sodium hydroxide

2024 Author: Angel Austin | [email protected]. Last modified: 2024-01-02 17:39

In the modern world, life is impossible without chemical reactions that take place everywhere and are both beneficial and dangerous. According to the periodic table of chemical elements of D. I. Mendeleev, metals of the 1st group of the main subgroup, which include sodium (Na), react violently with water, forming alkalis - chemically active substances.

The concept of alkalis

Water-soluble hydroxides of active metals - alkalis - caustic and rather dangerous chemicals. They are solid and white in color. Dissolving in water, these bases release heat. Alkalis are also capable of destroying skin, wood, fabrics, as a result of which they received the trivial name "caustic", which is usually applied only to alkali metal hydroxides. The most well-known alkalis include the hydroxides of sodium (NaOH), potassium (KOH), lithium (LiOH), barium (Ba(OH)₂), cesium (CsOH), calcium (Ca(OH)_{2) and some others.}

Sodium hydroxide: characteristics

Caustic soda is trivi althe name of sodium hydroxide - one of the most common alkalis. It belongs to dangerous 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 the release of heat and is a white, hygroscopic, that is, capable of absorbing water vapor from the air, compound. The density of caustic soda is 2.13 g/cm³.

Reactivity

Caustic soda solution can enter into reactions of various types, forming other substances.

1. When this compound reacts with acids, s alt and water are always formed:

NaOH + HCl=NaCl₂ + H_2O.

2. Caustic soda is able to react with acidic and amphoteric metal oxides (in solution and when fused), also forming the corresponding s alt and water:

• 2NaOH + SO₃=Na₂SO₄ + H ₂O (SO_{3 – acid oxide);}
• 2NaOH + ZnO=Na₂ZnO₂ + H_{2O (ZnO – amphoteric oxide, this reaction proceeds by fusion and heating).}

When sodium hydroxide reacts with an amphoteric oxide solution, a soluble complex s alt is formed.

3. The reaction of alkali with amphoteric hydroxides also leads to the formation of a melt or a complex sodium s alt, depending on its conditions.

4. By reacting the caustic with s alts, sodium and the corresponding water-insoluble hydroxide are obtained.

• 2NaOH + MgCl₂=2NaCl + Mg(OH)_{2 (magnesium hydroxide is a water-insoluble base).}

5. Sodium hydroxide can also react with non-metals, such as sulfur or halogens to form a mixture of sodium s alts, as well as with amphoteric metals to form complex s alts, iron and copper.

• 3S + 6NaOH=2Na₂S + Na₂SO₄ + 3H _2O.

6. Caustic soda is also able to interact with organic substances, for example: esters, amides, polyhydric alcohols.

• 2C₂H₆O₂ + 2NaOH=C₂ H₄O₂Na₂ + 2H_{2 O (the reaction product is sodium alcoholate).}

Receive

There are several methods for producing caustic soda in industry, the main ones being chemical and electrochemical.

The first method is based on several methods: pyrolysis, lime and ferrite.

1. Pyrolysis is carried out by calcining sodium carbonate at a high temperature (at least 1000 degrees) with the formation of sodium oxide and carbon dioxide. Next, the resulting cooled oxide is dissolved in water, as a result of which caustic soda is obtained.

• Na₂CO₃=Na₂O + CO _{2 (at 1000 degrees);}
• Na₂O + H₂O=_2NaOH.

Sometimes sodium bicarbonate is used instead of sodium carbonate, and the process is therefore a bit more complicated.

2. The lime method for producing sodium hydroxide consists in the interaction of the sodium s alt of carbonic acid with calcium hydroxide (slaked 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 from the main solution.}

• Na₂CO₃ + Ca(OH)₂=2NaOH + CaCO _3.

3. The ferrite method is carried out in two stages: first, soda is fused with iron oxide III at temperatures up to 1200 degrees to obtain sodium ferrite, then the latter is treated with water, resulting in alkali.

• Na₂CO₃ + Fe₂O₃ =2NaFeO₂ + CO_2;
• 2NaFeO₂ + 2H₂O=2NaOH + Fe₂O3H _2O.

In the electrochemical method of obtaining caustic soda, several methods are also used: electrolysis of a sodium chloride solution (NaCl), diaphragm, membrane and mercury method with a liquid cathode. The last three methods are more complex than the first, but they are all associated with passing an electric current through the solution of the corresponding s alts, that is, with electrolysis.

The most common method for producing alkali is the electrolysis of a halite solution, consisting of table waters alt, as a result of which chlorine and hydrogen are released at the anode and cathode, and sodium hydroxide is obtained:

• 2NaCl + 2H₂O=H₂ + Cl_{2 + 2NaOH.}

In the laboratory, caustic soda is also produced by chemical methods, but diaphragm and membrane methods are most commonly used.

Application

Caustic soda is used not only in various industries, but also in everyday life. It is used:

1. In the production of detergents.
2. For acid neutralization or as a catalyst in chemical industries.
3. For making biodiesel, which is more environmentally friendly than conventional diesel.
4. Dry granules are made from it, with the help of which they clean sewer pipes and sinks from food blockages.
5. Caustic soda is also applicable in the manufacture of food products such as bread or cocoa. It is used as a food supplement.
6. In cosmetology, the substance is used to remove dead skin.
7. For faster photo processing.
8. Technical caustic soda is widely used in chemical, petrochemical, oil refining, pulp and paper, mining, textile, food and many other industries.

Precautions

Caustic soda is a strong base. It can easily damage not only tissue, but also human skin, which will be accompanied byburns. When working with this substance, certain safety precautions must be observed, namely:

• It is necessary to wear special rubber gloves, goggles to prevent the solution from getting on hands and eyes.
• You need to wear clothes that will be resistant to chemical compounds and will not allow them to get on the skin of the body. Usually such clothes are treated with PVC.