Chemistry is a science that studies the various reactions that occur in nature, as well as the interactions of some compounds with others. The main substances here are acids and alkalis, the reactions between which are usually called neutralization. They lead to the formation of water-soluble salts.
What is alkali
Hydroxides of alkali (metals of the first group of the main (A) subgroup in the periodic table of chemical elements of D.I. Mendeleev) and alkaline-earth (metals of the second group of the main (A) subgroup, including calcium) of metals that interact violently with water and completely dissolve in it, called alkalis. Since they are capable of destroying organic material (skin, wood, paper), they are called caustic. For example, potassium hydroxide (KOH) - caustic potassium, barium (Ba (OH) 2 ) - caustic barium and so on.
Physical properties of strong bases
Based on the definition of what alkali is, we can add that these hydroxides are also solid hygroscopic (capable of absorbing water vapor from air) substances of white color. The strongest alkalis include hydroxides of cesium CsOH and radium Ra (OH) 2 . Alkali reactions are most often accompanied by heat (exothermic). Also, the physical properties of such bases include their ability to dissolve in some organic compounds, for example, in alcohols: methanol and ethanol.
Chemical properties
Alkaline solutions can enter into various reactions.
Strong bases have the ability to interact with acidic and amphoteric oxides:
- KOH + SO3 = K2SO4 + H2O (SO3 - acid oxide);
- 2KOH + Al2O3 = 2KAlO2 + H2O (fusion reaction, takes place when heated, where Al2O3 is amphoteric oxide);
- 2KOH + Al2O3 + 3H2O = 2K [Al (OH) 4] (the reaction proceeds with the formation of a soluble complex salt - potassium tetrahydroxoaluminate).
When reacting with amphoteric metals (Zn, Al and others), it is also possible to form both a melt and the corresponding complex salt. Moreover, both reactions are accompanied by the release of gaseous hydrogen:
- 2KOH + 2Al = 2KAlO2 + H2;
- 2KOH + 2Al + 6H2O = 2K [Al (OH) 4] + 3H2.
Also, alkalis are able to react with salts, resulting in the formation of another base and another salt. The prerequisite for the reaction is that as a result one of the substances formed should be insoluble in water:
NaOH + CuSO4 = Na2SO4 + Cu (OH) 2.
As already mentioned earlier, alkalis and acids enter into a neutralization reaction, salt and water are formed:
NaOH + HCl = NaCl + H2O.
Alkalis only react with other bases if they are amphoteric metal hydroxides:
NaOH + Al (OH) 3 = Na [Al (OH) 4].
Some of them can interact with many organic substances: esters, amides, polyhydric alcohols:
2C2H6O2 + 2NaOH = C2H4O2Na2 + 2H2O (the reaction product is sodium alcoholate).
How to get a strong foundation
Alkalis are obtained in many ways both in industry and in laboratories.
In the industrial industry, there are several methods for producing alkalis: pyrolysis, calcareous, ferritic, electrolysis, which is divided into diaphragm, membrane and mercury methods on liquid and solid cathodes.
This is the electrolysis of solutions of sodium and potassium chlorides, after which chlorine and hydrogen are released at the anode and cathode, and the corresponding hydroxides are obtained:
- 2NaCl + 2H2O = H2 + Cl2 + 2NaOH;
- 2KCl + 2H2O = H2 + Cl2 + 2KOH.
When pyrolysis of 1000 degrees in the first stage, the formation of sodium oxide occurs:
Na2CO3 = Na2O + CO2.
At the second stage, the obtained cooled oxide is dissolved in water, as a result of which the necessary alkali is obtained:
Na2O + H2O = 2NaOH.
The laboratories also use electrolysis. Even alkalis can be obtained by exposure to the corresponding metals with water or by the interaction of salts of these metals with other bases, resulting in the necessary alkali and the second reaction product insoluble in water - salt.
When cesium and water interact, cesium hydroxide is obtained and hydrogen is released (the reaction proceeds even at a temperature of -120 degrees):
2Cs + 2H2O = 2CsOH + H2.
As a result of the action of water on lithium oxide, an alkali is obtained:
Li2O + 2H2O = 2LiOH + H2.
Application
Based on the very definition of what alkali is, one can understand that they are widely used not only in industry, but also in everyday life:
- Disinfection of ponds during fishing.
- As a fertilizer.
- In the pharmaceutical industry.
- By paper production.
- Synthetic rubber production.
- Getting soap and detergents.
- Electrolyte components in alkaline batteries.
- Carbon dioxide absorber (lithium hydroxide).
- Lubricant production.
- Dyes in the manufacture of food (food additives).
- Battery electrolytes (potassium hydroxide).
- Cleaning sewer pipes and sinks from food blockages.
- Acid neutralization.
- Catalysts in the chemical industries.
- Chemical photo processing.
Precautions
It becomes apparent that alkalis such as hydroxides of sodium, lithium, potassium, cesium and others can severely damage and burn the skin and mucous membranes of the eyes even when the smallest particles of the compound get there. To prevent this, it is necessary to wear safety glasses, rubber gloves, as well as overalls that are treated with special substances that do not allow the material to interact with alkalis.