Of the inorganic medicinal substances, acids, alkalis, salts of alkali and alkaline earth metals are of the greatest importance for the body. These compounds are electrolytes, i.e. dissociate into ions in solution.
acids
(diluted hydrochloric acid and 0.1 N solution, boric acid, salicylic acid, etc.)
The biological effect of acids depends mainly on hydrogen ions, therefore, their activity is determined by the degree of dissociation. During the dissociation of most acids, the anion does not play a significant role in the action of the acid. The exception is hydrocyanic acid (HC), the toxic properties of which depend on the C anion.
local action.
Acids, interacting with whites of the skin and mucous membranes, form dense albuminates that are insoluble in water and do not penetrate deep into the tissue.
At low concentrations, the acid has an astringent (anti-inflammatory) effect, and at higher concentrations, it has an irritating and cauterizing effect. The astringent effect is more pronounced in weak acids; cauterizing - in the strong. Weakly dissociate, for example, boric and salicylic acids, they have anti-inflammatory, antibacterial, antifungal effects, are used as antiseptics, depending on the concentration, salicylic acid has keratoplastic (stimulates epithelization) 1-2%, or keratolytic (scaly) 10-20% action.
The local action of acids is accompanied by reflex reactions, their magnitude and nature depend on the intensity of the action of the acid.
Strong inorganic acids (sulfuric, hydrochloric, nitric) cause coagulative necrosis; they take away water and form a dense albuminate on the surface of the tissue - a dry scab.
Of particular interest is the effect of acids on the secretion and motility of the gastrointestinal tract. This action was studied by the school of IP Pavlov. Acids are necessary for digestion (for example, dilute hydrochloric acid), they contribute to the action of pepsin, increase the secretion of gastric and pancreatic juices, delay the transfer of stomach contents into the 12-colon, because getting into it causes a contraction of the pyloric part of the stomach, which only relaxes after acid neutralization.
resorptive action.
After absorption into the blood or parenteral administration, acids are immediately neutralized by buffer systems and do not have a resorptive effect.
When a large amount of acids enters the blood, alkaline reserves are depleted and first compensated, then uncompensated acidosis develops (pH<7,35).
Thus, the clinic of acid poisoning consists of the symptoms of their local action and the phenomena of uncompensated acidosis (coma, depressed breathing, drop in blood pressure).
Help measures: Remove acid from the surface of the skin with water or a weak solution of alkali (soda-hydrocarbonate Na). If the acid is taken orally, it is neutralized with a weak alkali - magnesium oxide. To prevent shock, narcotic analgesics (promedol, omnopon), antispasmodics (atropine, no-shpa) are administered. Means of specific therapy for acidosis (Na bicarbonate, trisamine), carry out symptomatic and dosing therapy.
(caustic soda), KOH (caustic potassium), Ba (OH) 2 (caustic barium). As an exception, monovalent thallium hydroxide TlOH can be attributed to alkalis, which is highly soluble in water and is a strong base. Caustic alkalis are the trivial name for lithium hydroxides LiOH, sodium NaOH, potassium KOH, rubidium RbOH, and cesium CsOH.
Physical properties
Alkali metal hydroxides (caustic alkalis) are solid, white, very hygroscopic substances. Alkalis are strong bases, very soluble in water, and the reaction is accompanied by significant heat release. Base strength and solubility in water increase with increasing cation radius in each group of the periodic table. The strongest alkalis are cesium hydroxide (since, due to the very short half-life, francium hydroxide is not produced in macroscopic quantities) in group Ia and radium hydroxide in group IIa. In addition, caustics are soluble in ethanol and methanol.
Chemical properties
Alkalis exhibit basic properties. In the solid state, all alkalis absorb H 2 O from the air, as well as CO 2 (also in the state of solution) from the air, gradually turning into carbonates. Alkalis are widely used in industry.
Qualitative reactions to alkalis
Aqueous alkali solutions change the color of indicators.
| Indicator and transition number |
X | pH interval and transition number |
Colour alkaline form |
|
|---|---|---|---|---|
| methyl violet | 0.13-0.5 [I] | green | ||
| Cresol Red [I] | 0.2-1.8 [I] | yellow | ||
| methyl violet | 1,0-1,5 | blue | ||
| Thymol blue [I] | to | 1.2-2.8 [I] | yellow | |
| Tropeolin 00 | o | 1,3-3,2 | yellow | |
| methyl violet | 2,0-3,0 | Violet | ||
| (Di)methyl yellow | o | 3,0-4,0 | yellow | |
| Bromophenol blue | to | 3,0-4,6 | blue-violet | |
| Congo red | 3,0-5,2 | blue | ||
| methyl orange | o | 3,1-(4,0)4,4 | (orange-)yellow | |
| Bromocresol green | to | 3,8-5,4 | blue | |
| Bromocresol blue | 3,8-5,4 | blue | ||
| Lakmoid | to | 4,0-6,4 | blue | |
| methyl red | o | 4,2(4,4)-6,2(6,3) | yellow | |
| Chlorophenol red | to | 5,0-6,6 | red | |
| Litmus (azolithine) | 5,0-8,0 (4,5-8,3) | blue | ||
| Bromocresol purple | to | 5,2-6,8(6,7) | bright red | |
| Bromothymol blue | to | 6,0-7,6 | blue | |
| Neutral red | o | 6,8-8,0 | amber yellow | |
| Phenol red | about | 6,8-(8,0)8,4 | bright red | |
| Cresol Red | to | 7,0(7,2)-8,8 | Dark red | |
| α-Naphtholphthalein | to | 7,3-8,7 | blue | |
| thymol blue | to | 8,0-9,6 | blue | |
| Phenolphthalein [I] | to | 8.2-10.0 [I] | crimson red | |
| thymolphthalein | to | 9,3(9,4)-10,5(10,6) | blue | |
| Alizarin yellow LJ | to | 10,1-12,0 | brown yellow | |
| Nile blue | 10,1-11,1 | red | ||
| diazo violet | 10,1-12,0 | Violet | ||
| indigo carmine | 11,6-14,0 | yellow | ||
| Epsilon Blue | 11,6-13,0 | dark violet | ||
Interaction with acids
Alkalis, like bases, react with acids to form salt and water (neutralization reaction). This is one of the most important chemical properties of alkalis.
Alkali + Acid → Salt + Water
; .
Interaction with acid oxides
Alkalis interact with acidic oxides to form salt and water:
Alkali + Acid oxide → Salt + Water
;
Interaction with amphoteric oxides
.Interaction with transition metals
Alkali solutions react with metals, which form amphoteric oxides and hydroxides ( and etc). The equations of these reactions in a simplified form can be written as follows:
; .
In reality, in the course of these reactions, hydroxo complexes are formed in solutions (hydration products of the above salts):
; ;
Interaction with salt solutions
Alkali solutions interact with salt solutions if an insoluble base or insoluble salt is formed:
Alkali solution + Salt solution → New base + New salt
; ;
Receipt
Soluble bases are obtained in various ways.
Hydrolysis of alkali/alkaline earth metals
Obtained by electrolysis of alkali metal chlorides or by the action of water on alkali metal oxides.
Application
Alkalis are widely used in various industries and medicine; also for disinfection of ponds in fish farming and as a fertilizer, as an electrolyte for alkaline batteries.
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Notes
Literature
- Kolotov S.S.,.// Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
- Glossary of terms in chemistry // J. Opeida, O. Schweika. Institute of Physical and Organic Chemistry and Coal Chemistry im. L.M. Litvinenka National Academy of Sciences of Ukraine, Donetsk National University - Donetsk: "Weber", 2008. - 758 p. - ISBN 978-966-335-206-0
An excerpt characterizing alkalis
- Here. What lightning! they were talking.In the abandoned tavern, in front of which stood the doctor's wagon, there were already about five officers. Marya Genrikhovna, a plump blond German woman in a blouse and nightcap, was sitting in the front corner on a wide bench. Her husband, the doctor, slept behind her. Rostov and Ilyin, greeted with cheerful exclamations and laughter, entered the room.
- AND! what fun you have, ”said Rostov, laughing.
- And what are you yawning?
- Good! So it flows from them! Don't wet our living room.
“Don’t get Marya Genrikhovna’s dress dirty,” the voices answered.
Rostov and Ilyin hurried to find a corner where, without violating the modesty of Marya Genrikhovna, they could change their wet clothes. They went behind the partition to change their clothes; but in a small closet, filling it all up, with one candle on an empty box, three officers were sitting, playing cards, and would not give up their place for anything. Marya Genrikhovna gave up her skirt for a while in order to use it instead of a curtain, and behind this curtain, Rostov and Ilyin, with the help of Lavrushka, who brought packs, took off their wet and put on a dry dress.
A fire was kindled in the broken stove. They took out a board and, having fixed it on two saddles, covered it with a blanket, took out a samovar, a cellar and half a bottle of rum, and, asking Marya Genrikhovna to be the hostess, everyone crowded around her. Who offered her a clean handkerchief to wipe her lovely hands, who put a Hungarian coat under her legs so that it would not be damp, who curtained the window with a raincoat so that it would not blow, who fanned the flies from her husband’s face so that he would not wake up.
“Leave him alone,” said Marya Genrikhovna, smiling timidly and happily, “he sleeps well after a sleepless night.
“It’s impossible, Marya Genrikhovna,” answered the officer, “you must serve the doctor.” Everything, maybe, and he will take pity on me when he cuts his leg or arm.
There were only three glasses; the water was so dirty that it was impossible to decide when the tea was strong or weak, and there was only six glasses of water in the samovar, but it was all the more pleasant, in turn and seniority, to receive your glass from Marya Genrikhovna’s plump hands with short, not quite clean nails . All the officers really seemed to be in love with Marya Genrikhovna that evening. Even those officers who were playing cards behind the partition soon gave up the game and went over to the samovar, obeying the general mood of wooing Marya Genrikhovna. Marya Genrikhovna, seeing herself surrounded by such brilliant and courteous youth, beamed with happiness, no matter how hard she tried to hide it and no matter how obviously shy at every sleepy movement of her husband sleeping behind her.
There was only one spoon, there was most of the sugar, but they did not have time to stir it, and therefore it was decided that she would stir the sugar in turn for everyone. Rostov, having received his glass and poured rum into it, asked Marya Genrikhovna to stir it.
- Are you without sugar? she said, smiling all the time, as if everything she said, and everything others said, was very funny and had another meaning.
- Yes, I don’t need sugar, I just want you to stir with your pen.
Marya Genrikhovna agreed and began to look for the spoon, which someone had already seized.
- You're a finger, Marya Genrikhovna, - said Rostov, - it will be even more pleasant.
- Hot! said Marya Genrikhovna, blushing with pleasure.
Ilyin took a bucket of water and, dropping rum into it, came to Marya Genrikhovna, asking her to stir it with her finger.
“This is my cup,” he said. - Just put your finger in, I'll drink it all.
When the samovar was all drunk, Rostov took the cards and offered to play kings with Marya Genrikhovna. A lot was cast as to who should form the party of Marya Genrikhovna. The rules of the game, at the suggestion of Rostov, were that the one who would be the king had the right to kiss the hand of Marya Genrikhovna, and that the one who remained a scoundrel would go to put a new samovar for the doctor when he wakes up.
“Well, what if Marya Genrikhovna becomes king?” Ilyin asked.
- She's a queen! And her orders are the law.
The game had just begun, when the doctor's confused head suddenly rose from behind Marya Genrikhovna. He had not slept for a long time and listened to what was said, and apparently did not find anything cheerful, funny or amusing in everything that was said and done. His face was sad and dejected. He did not greet the officers, scratched himself and asked for permission to leave, as he was blocked from the road. As soon as he left, all the officers burst into loud laughter, and Marya Genrikhovna blushed to tears, and thus became even more attractive to the eyes of all the officers. Returning from the courtyard, the doctor told his wife (who had already ceased to smile so happily and, fearfully awaiting the verdict, looked at him) that the rain had passed and that we had to go to spend the night in a wagon, otherwise they would all be dragged away.
- Yes, I'll send a messenger ... two! Rostov said. - Come on, doctor.
"I'll be on my own!" Ilyin said.
“No, gentlemen, you slept well, but I haven’t slept for two nights,” said the doctor, and sat down gloomily beside his wife, waiting for the game to be over.
Looking at the gloomy face of the doctor, looking askance at his wife, the officers became even more cheerful, and many could not help laughing, for which they hastily tried to find plausible pretexts. When the doctor left, taking his wife away, and got into the wagon with her, the officers lay down in the tavern, covering themselves with wet overcoats; but they didn’t sleep for a long time, now talking, remembering the doctor’s fright and the doctor’s merriment, now running out onto the porch and reporting what was happening in the wagon. Several times Rostov, wrapping himself up, wanted to fall asleep; but again someone's remark amused him, again the conversation began, and again there was heard the causeless, cheerful, childish laughter.
At three o'clock, no one had yet fallen asleep, when the sergeant-major appeared with the order to march to the town of Ostrovna.
All with the same accent and laughter, the officers hurriedly began to gather; again put the samovar on the dirty water. But Rostov, without waiting for tea, went to the squadron. It was already light; The rain stopped, the clouds dispersed. It was damp and cold, especially in a damp dress. Leaving the tavern, Rostov and Ilyin both in the twilight of dawn looked into the doctor's leather tent, glossy from the rain, from under the apron of which the doctor's legs stuck out and in the middle of which the doctor's bonnet was visible on the pillow and sleepy breathing was heard.
"Really, she's very nice!" Rostov said to Ilyin, who was leaving with him.
- What a lovely woman! Ilyin replied with sixteen-year-old seriousness.
Half an hour later, the lined up squadron stood on the road. The command was heard: “Sit down! The soldiers crossed themselves and began to sit down. Rostov, riding forward, commanded: “March! - and, stretching out to four people, the hussars, sounding with the slap of hooves on the wet road, the strumming of sabers and a low voice, set off along the large road lined with birches, following the infantry and the battery walking ahead.
Broken blue-lilac clouds, reddening at sunrise, were quickly driven by the wind. It got brighter and brighter. One could clearly see that curly grass that always sits along country roads, still wet from yesterday's rain; the hanging branches of the birch trees, also wet, swayed in the wind and dropped light drops to the side. The faces of the soldiers became clearer and clearer. Rostov rode with Ilyin, who did not lag behind him, along the side of the road, between a double row of birches.
Rostov in the campaign allowed himself the freedom to ride not on a front-line horse, but on a Cossack. Both a connoisseur and a hunter, he recently got himself a dashing Don, large and kind playful horse, on which no one jumped him. Riding this horse was a pleasure for Rostov. He thought of the horse, of the morning, of the doctor's wife, and never once thought of the impending danger.
Alkali (synonymous with alkali) is the name of any of the soluble hydroxides of alkali metals, that is, lithium, sodium, potassium, rubidium and cesium. Alkalis are strong bases and react with acids to form neutral salts. They are caustic and in concentrated form are corrosive to organic tissues. The term alkali is also applied to soluble hydroxides of alkaline earth metals such as calcium, strontium and barium, as well as to ammonium hydroxide. The name of the substance, alkali, was originally applied to the ashes of burnt plants containing sodium or potassium, from which oxides of sodium or potassium could be leached.
Among all alkalis produced by the industry, the largest share of such productions falls on the production of soda ash (Na2CO3 - sodium carbonate) and caustic soda (NaOH - sodium hydroxide). Potassium hydroxide (KOH-caustic potash) and magnesium hydroxide (Mg(OH)2-magnesium hydrate) are next in terms of production.
The production of a wide range of consumer products depends on the use of alkalis at some stage. Soda ash and caustic soda are important in the production of glass, soap, viscose, cellophane, paper, cellulose, detergents, textiles, water softeners, certain metals (especially aluminium), soda bicarbonate, gasoline and many other petroleum products and chemicals. .
A few historical moments from the history of alkali production.
People have been using alkali for centuries, getting it first from the leaching (water solutions) of certain desert lands. Until the end of the 18th century, leaching from wood ash or seaweed was the main source of alkali. In 1775, the French Academy of Sciences offered cash prizes for new methods of production. alkalis. The prize for soda ash was awarded to the Frenchman Nicolas Leblanc, who in 1791 patented the process of converting sodium chloride to sodium carbonate.
The Leblanc method of production dominated world production until the end of the 19th century, but after the First World War it was completely superseded by another method of salt conversion, which was perfected in the 1860s by Ernest Solve of Belgium. At the end of the 19th century, electrolytic methods for the production of caustic soda appeared, the volumes of which grew rapidly.
In the Solve method, the ammonia-soda process for the production of soda ash proceeded as follows: table salt in the form of a strong brine was chemically treated to remove calcium and magnesium impurities and then saturated with ammonia recycle gas in towers. Thereafter, the ammonia brine was gassed using carbon dioxide gas at moderate pressure in a different type of tower. These two processes give ammonium bicarbonate and sodium chloride, the double decomposition of which gives the desired sodium bicarbonate, as well as ammonium chloride. The sodium bicarbonate is then heated until it decomposes to the required sodium carbonate. The ammonia involved in the process is almost completely recovered by treatment with ammonium chloride and lime to produce ammonia and calcium chloride. The recovered ammonia is then reused in the processes described above.
The electrolytic production of caustic soda involves the electrolysis of a strong salt solution in an electrolytic cell. (Electrolysis is the breaking down of a compound in solution into its constituents using an electric current in order to cause a chemical change.) Electrolysis of sodium chloride yields chlorine, sodium hydroxide, or metallic sodium. Sodium hydroxide in some cases competes with sodium carbonate in the same process applications. And in any case, both are interconvertible through fairly simple processes. Sodium chloride can be
converted to alkali by one of two processes, the only difference being that the ammonia-soda reaction process produces chlorine in the form of calcium chloride, a compound of little economic value, while the electrolytic processes produce elemental chlorine, which has countless uses in chemical industry.
In several places in the world there are significant reserves of minerala form of soda ash known as natural lye. Such deposits produce most of the world's natural alkali from vast deposits in underground mines.
Natural sodium metal.
Read the article Alkalis (source "Encyclopedic Dictionary of a Chemist") and get a better understanding of what an alkali is, or watch a video about this chemical reagent.
The use of alkali in our environment
Alkali has gained wide application in our life. Alkali can be used to soften water in one form or another and remove impurities such as manganese, fluorides and organic tannins. Heavy industries use alkali in the form of lime to absorb and neutralize sulfur oxides in atmospheric emissions, thereby reducing the chance of acid precipitation. Sulfur dioxide produced by industrial plants and released into the atmosphere returns to earth in the form of acid rain or sulfuric acid. Such areas exposed to acid rain are treated with the help of aviation with preparations that include alkali. This makes it possible to control and neutralize the critical pH level of water and soil in areas where such man-made emissions have occurred. Introduction of alkali into waste and waste water, maintaining the correct pH level in oxidative processes during their decomposition. Stabilizes sludge formation in wastewater and reduces odor or formation of pathogenic bacteria. The sludge from wastewater bodies treated with quicklime complies with environmental standards, which makes it suitable for further use as a fertilizer on agricultural lands.
Industrial applications of alkali
In industrial and mining operations, the use of alkalis in wastewater helps to neutralize harmful compounds and clean them up. Treatment with excess alkali, raises the pH of the water to 10.5-11, and can disinfect the water and remove heavy metals. Alkalis such as lime are key in the chemical production of calcium carbide, citric acid, petrochemicals and magnesia. In the paper industry, calcium carbonate is a caustic agent for bleaching. The steel industry depends on lime as a component to remove impurities such as gaseous carbon monoxide, silicon, manganese and phosphorus.
Detergents formed by alkali
Alkaline detergents help with cleaning heavily soiled surfaces. These economical, water-soluble alkalis with a pH of 9 to 12.5 can neutralize acids in various types of dirt and deposits.
Alkali in the production of glass and ceramics
Alkali is the main raw material in glass production. Limestone, as well as sand, soda ash, lime and other chemicals, are fired at extremely high temperatures and turned into a molten mass. Glassblowers and potters use alkalis for glazes and fluxes, which react with acids to form silicates (glass) when heated. Concentrated alkalis create a richer color in the glaze.
Alkali Literature
In the book by I. Nechaev "Stories about the Elements", published in 1940, in an accessible and understandable language for the layman 
talks about what alkali is and how it differs from another caustic substance - acid. Excerpt from the text:
"Among the numerous substances that chemists have used in their laboratories for a long time, caustic alkalis have always occupied a place of honor - caustic potash and caustic soda. Hundreds of different chemical reactions are carried out in laboratories, factories and at home with the participation of alkalis. With the help of caustic potash and Soda can, for example, make most insoluble substances soluble, and the strongest acids and suffocating vapors can, thanks to alkalis, be deprived of all their burning and poisonousness.
Caustic alkalis are very peculiar substances. In appearance, these are whitish, rather hard stones, as if unremarkable. But try to take caustic potash or soda and hold it in your hand. You will feel a slight burning sensation, almost like touching nettles. It would be unbearably painful to hold caustic alkalis in your hand for a long time: they can corrode the skin and meat to the bone. That is why they are called "caustic", in contrast to other, less "evil" alkalis - the well-known soda and potash. From soda and potash, by the way, almost always caustic soda and potassium were obtained.
Caustic alkalis have a strong attraction to water. Leave a piece of completely dry caustic potash or soda in the air. After a short time, no one knows where liquid will appear on its surface, then it will become all wet and loose, and in the end it will spread into a shapeless mass, like jelly. This alkali attracts water vapor from the air and forms a thick solution with moisture. Whoever has to dip his fingers in a solution of caustic alkali for the first time, he declares with surprise: - Like soap! And this is absolutely correct. Lye is slippery like soap. Moreover, soap is “soapy” to the touch because it is made with alkalis. A solution of caustic alkali tastes like soap.
But a chemist recognizes a caustic alkali not by taste, but by how this substance behaves with litmus paint and with acids. A piece of paper soaked in blue litmus paint instantly turns red when dipped in acid; and if this reddened piece of paper is touched with alkali, then it immediately turns blue again. Caustic alkali and acid cannot peacefully exist side by side for a single second. They immediately enter into a violent reaction, hissing and warming up, and destroy each other until not a grain of alkali or a drop of acid remains in the solution. Only then does peace come. Alkali and acid "neutralized" each other, they say in such cases. By combining them together, a "neutral" salt is obtained - neither sour nor caustic. So, for example, from the combination of burning hydrochloric acid with caustic soda, ordinary table salt is obtained.
Distinctive features of alkali.
From what we have read above, we already know that the opposite of alkali is acid. Instead of a bitter taste 
inherent in alkali, acids tend to taste sour. An example would be foods such as lemons or fruit vinegar (diluted), which are essentially acidic foods and contain acid. We can tell if a substance is an alkali or an acid by knowing its pH. The pH level is measured using the pH scale; this scale ranges from 0-14 and these numbers tell us whether a substance is an alkali or an acid. Pure distilled water has a pH of 7 and is called neutral (right in the middle of the scale). Any substance that has a pH greater than 7 is an alkaline substance, which may also be referred to as alkali. And, any other substance that has a pH below 7 is an acid.
Why is the substance alkaline?
Thus, we already know that the pH level is a scale whose values range from 0-14 and indicate whether a substance is alkaline or acidic. However, we don't really know why. Let's look at this issue in more detail.
The pH level of a substance depends on how the atoms are arranged and combined in the substance. Pure water is right in the middle of the scale and has a pH of 7. This means that it contains an equal number of hydrogen atoms (H+) and hydroxide atoms (OH-). When a substance has more hydrogen atoms (H+), it is an acid. When a substance has more hydroxide atoms (OH-), it is alkaline.
Where to buy alkali?
You can buy alkali in Novosibirsk with a degree of purification of NDA (pure for analysis) in the Dlya delo store on the order page: or. For non-resident buyers, the goods can be sent by Russian Post or transport companies.
Insoluble base: copper hydroxide
Foundations- called electrolytes, in the solutions of which there are no anions, except for hydroxide ions (anions are ions that have a negative charge, in this case they are OH - ions). Titles grounds consists of three parts: words hydroxide , to which the name of the metal is added (in the genitive case). For example, copper hydroxide(Cu(OH) 2). For some grounds old names may be used, for example sodium hydroxide(NaOH) - sodium alkali.
Sodium hydroxide, sodium hydroxide, sodium alkali, caustic soda- all this is the same substance, the chemical formula of which is NaOH. Anhydrous sodium hydroxide is a white crystalline substance. A solution is a clear liquid that looks indistinguishable from water. Be careful when using! Caustic soda burns the skin severely!
The classification of bases is based on their ability to dissolve in water. Some properties of bases depend on solubility in water. So, grounds that are soluble in water are called alkali. These include sodium hydroxides(NaOH), potassium hydroxide(KOH), lithium (LiOH), sometimes they are added to their number and calcium hydroxide(Ca (OH) 2)), although in fact it is a slightly soluble white substance (slaked lime).
Getting the grounds
Getting the grounds and alkalis can be done in various ways. To receive alkalis You can use the chemical interaction of metal with water. Such reactions proceed with a very large release of heat, up to ignition (ignition occurs due to the release of hydrogen during the reaction).
2Na + 2H 2 O → 2NaOH + H 2
Quicklime - CaO CaO + H 2 O → Ca (OH) 2
But in industry, these methods have not found practical value, of course, except for the production of calcium hydroxide Ca (OH) 2. Receipt sodium hydroxide and potassium hydroxide associated with the use of electricity. During the electrolysis of an aqueous solution of sodium or potassium chloride, hydrogen is released at the cathode, and chlorine at the anode, while in the solution where electrolysis occurs, accumulates alkali!
KCl + 2H 2 O → 2KOH + H 2 + Cl 2 (this reaction takes place when an electric current is passed through the solution).
Insoluble bases besiege alkalis from solutions of the corresponding salts.
CuSO 4 + 2NaOH → Cu(OH) 2 + Na 2 SO 4
Base properties
alkalis heat resistant. Sodium hydroxide you can melt and bring the melt to a boil, while it will not decompose. alkalis easily react with acids, resulting in the formation of salt and water. This reaction is also called the neutralization reaction.
KOH + HCl → KCl + H2O
alkalis interact with acidic oxides, as a result of which salt and water are formed.
2NaOH + CO 2 → Na 2 CO 3 + H 2 O
Insoluble bases, unlike alkalis, are not thermally stable substances. Some of them, for example, copper hydroxide, decompose when heated,
Cu(OH) 2 + CuO → H 2 O
others - even at room temperature (for example, silver hydroxide - AgOH).
Insoluble bases interact with acids, the reaction occurs only if the salt that is formed during the reaction dissolves in water.
Cu(OH) 2 + 2HCl → CuCl 2 + 2H 2 O
Dissolution of an alkali metal in water with a change in the color of the indicator to bright red Alkali metals are metals that react with water to form alkali. Sodium Na is a typical representative of alkali metals. Sodium is lighter than water, so its chemical reaction with water occurs on its surface. Actively dissolving in water, sodium displaces hydrogen from it, while forming sodium alkali (or sodium hydroxide) - caustic soda NaOH. The reaction proceeds as follows:
2Na + 2H 2 O → 2NaOH + H 2
All alkali metals behave in a similar way. If, before starting the reaction, the indicator phenolphthalein is added to the water, and then a piece of sodium is dipped into the water, then the sodium will slide through the water, leaving behind a bright pink trace of the formed alkali (the alkali turns phenolphthalein pink)
iron hydroxide
iron hydroxide is the basis. Iron, depending on the degree of its oxidation, forms two different bases: iron hydroxide, where iron can have valencies (II) - Fe (OH) 2 and (III) - Fe (OH) 3. Like the bases formed by most metals, both iron bases are insoluble in water.
iron hydroxide(II) - white gelatinous substance (precipitate in solution), which has strong reducing properties. Besides, iron hydroxide(II) very unstable. If to a solution iron hydroxide(II) add a little alkali, then a green precipitate will fall out, which darkens rather quickly and turns into a brown precipitate of iron (III).
iron hydroxide(III) has amphoteric properties, but its acidic properties are much less pronounced. Get iron hydroxide(III) is possible as a result of a chemical exchange reaction between an iron salt and an alkali. for example
Fe 2 (SO 4) 3 + 6 NaOH → 3 Na 2 SO 4 +2 Fe (OH) 3
Before distinguishing acids from alkalis, you need to understand the concepts of acid, alkali and base, after which we move on to the so-called indicators, with which you can easily distinguish between these substances.
What is an acid?
Acid is a chemical compound. Usually solutions of acids taste (those that can be tasted) are sour, examples include acetic, malic, ascorbic and citric acids. The composition of the acid includes hydrogen and oxygen, as well as additional elements (or a complex of elements), which usually give the name to the acid - nitric, sulfuric, carbonic, ethyl-sulfuric, etc.
Acid- This is a complex substance in the molecule of which there are one or more hydrogen atoms and an acid residue.
Features of acids
The characteristic chemical properties of an acid are:
- sour taste
- the ability to convert blue plant matter - litmus to red
- the presence in the acid molecule of one or more hydrogen atoms that can be exchanged for a metal to form a salt.
The properties of acids are determined by the fact that they are able to replace hydrogen atoms in their molecules with metal atoms. For example:
Basic properties of acids
The effect of acid solutions on indicators. Almost all acids (except silicic acid) are highly soluble in water. Solutions of acids in water change the color of special substances - indicators. It is by the color of the indicators that the presence of acid is determined. The litmus indicator turns red with acid solutions, the methyl orange indicator also turns red.
Reaction of acids with bases. This reaction is called a neutralization reaction. An acid reacts with a base to form a salt, in which the acid residue is always found unchanged. The second product of the neutralization reaction is necessarily water.
Interaction of acids with basic oxides. Since basic oxides are the closest relatives of bases, acids also enter into neutralization reactions with them. As in the case of reactions with bases, acids form salt and water with basic oxides. The salt contains the acid residue of the acid used in the neutralization reaction. In reaction with basic oxides, acids form salt and water. The salt contains the acid residue of the acid used in the neutralization reaction.
For example, phosphoric acid is used to clean iron from rust (iron oxides). Phosphoric acid, removing its oxide from the metal surface, reacts very slowly with iron itself. The iron oxide is converted into a soluble FePO4 salt, which is washed off with water along with acid residues.
The interaction of acids with metals. The metal must be sufficiently active (reactive) with respect to acids. For example, gold, silver, copper, mercury and some other metals do not react with acids with the release of hydrogen. Metals such as sodium, calcium, zinc - on the contrary - react very actively with the release of hydrogen gas and a large amount of heat.
What is alkali?
alkalis Water-soluble strong bases are called. If a substance contains hydroxy groups (OH) that can be cleaved off (like a single "atom") in reactions with other substances, then such a substance is a base.
grounds substances are called in which metal atoms are bonded to hydroxy groups. That is, alkali is a substance consisting of a metal and an OH group (hydroxo group). Alkali will neutralize the cystol with the production of water and salt.
Physical properties: alkali solutions in water are soapy to the touch, they corrode skin, fabrics, paper - caustic alkalis(caustic soda NaOH, caustic potash KOH). On the skin, they cause long non-healing wounds. Very hygroscopic.
How to distinguish acid from alkali?
You can distinguish an acid from an alkali by using indicators. Now there are quite a lot of indicators - substances that help determine the composition of the environment. The indicators change color depending on the composition of the medium. This happens because in an acidic and alkaline environment, the indicator molecules have a different structure.
For example indicator phenolphthalein in an acidic medium it is in the form of undissociated molecules, and the solution is colorless, and in an alkaline medium, in the form of singly charged anions, and the solution has a crimson color. Litmus turns red in an acidic environment and blue in an alkaline environment.
Tea it is also an indicator. Probably many have noticed that if you put lemon in strong black tea and even drop a few drops (add acid), then the tea will brighten. And if you dissolve baking soda (alkali) in it, it will darken.
The color of the indicator will change in acid and alkali solutions.
No wonder there is a common expression "litmus test". For the litmus indicator, they even came up with mnemonics with which you can remember the relationship between the color of the indicator and the substance being determined:
- Red litmus indicator - acid point out clearly
- Blue litmus indicator. Lye is here - don't be open!
