Acids and alkalis Means that correct acid-base balance. Salts of alkali and alkaline earth metals

Alkalis are water-soluble strong bases. At present, the Brönsted-Lowry and Lewis theory is accepted in chemistry, which defines acids and bases. According to this theory, acids are substances capable of splitting off a proton, and bases are substances that can donate an electron pair OH-. It can be said that bases are compounds that, when dissociated in water, form only anions of the form OH - . If it is quite simple, then alkalis are compounds consisting of a metal and a hydroxide ion OH -.

Alkalis are commonly referred to as hydroxides of alkali and alkaline earth metals.

All alkalis are bases, but not vice versa, the definitions “base” and “alkali” cannot be considered synonymous.

correct chemical name alkalis - hydroxide (hydroxide), for example, sodium hydroxide, potassium hydroxide. Often used are also names that have developed historically. Due to the fact that alkalis destroy materials of organic origin - leather, fabrics, paper, wood, they are called caustic: for example, caustic soda, caustic barium. However, the concept of "caustic alkalis" chemists define the hydroxides of alkali metals - lithium, sodium, potassium, rubidium, cesium.

Properties of alkalis

Alkalis are solids white color; hygroscopic, water soluble. Dissolution in water is accompanied by active heat release. They react with acids to form salt and water. This neutralization reaction is the most important of all the properties of alkalis. In addition, hydroxides react with acid oxides (forming oxygen-containing acids), with transition metals and their oxides, and with salt solutions.

Alkali metal hydroxides are soluble in methyl and ethyl alcohols, capable of withstanding temperatures up to +1000 °C (with the exception of lithium hydroxide).

Alkalis are active chemical reagents that absorb not only water vapor from the air, but also molecules of carbon dioxide and sulfur dioxide, hydrogen sulfide, and nitrogen dioxide. Therefore, hydroxides should be stored in a sealed container or, for example, air access to a vessel with alkali should be organized through a calcium chloride tube. Otherwise, the chemical reagent after storage in air will be contaminated with carbonates, sulfates, sulfides, nitrates and nitrites.

If we compare alkalis by chemical activity, then it increases when moving along the column of the periodic table from top to bottom.

Concentrated alkalis destroy glass, and alkali melts destroy even porcelain and platinum, so alkali solutions are not recommended to be stored in vessels with ground glass stoppers and taps, as plugs and taps can jam. Alkalis are usually stored in polyethylene containers.

It is alkalis, not acids, that cause more severe burns, as they are more difficult to wash off the skin and penetrate deep into the tissue. Rinse off the alkali with a non-concentrated solution of acetic acid. It is necessary to work with them in protective equipment. Alkaline burn requires immediate medical attention!

The use of alkalis

as electrolytes.
— For the production of fertilizers.
- In medicine, chemical, cosmetic industries.
- In fish farming for sterilization of ponds.

In the PrimeChemicalsGroup store you will find the most popular alkalis at competitive prices.

Sodium hydroxide

The most popular and demanded alkali in the world.

It is used for saponification of fats in the production of cosmetics and detergents, for the manufacture of oils in the process of oil refining, as a catalyst and reagent in chemical reactions; in the food industry.

caustic potash

It is used for the production of soap, potash fertilizers, electrolytes for batteries and accumulators, synthetic rubber. Also - as a dietary supplement; for professional cleaning of stainless steel products.

aluminum hydroxide

Demanded in medicine as an excellent adsorbent, antacid, enveloping agent; ingredient in pharmaceutical vaccines. In addition, the substance is used in sewage treatment plants and in the processes for obtaining pure aluminum.

calcium hydroxide

Popular lye with very a wide range application, which in everyday life is known as "slaked lime". It is used for disinfection, water softening, in the production of fertilizers, caustic soda, bleach, building materials. It is used to protect trees and wooden structures from pests and fire; in the food industry as food supplement and a reagent in the production of sugar.

What are acids, bases and bases from a chemical point of view? Read carefully and memorize. Look don't get confused!

What is an acid?

Acids are molecules that, when dissolved in water, release a hydrogen ion. Ions are positively and negatively charged particles that give acids their properties.

Let's look at this process using the example of hydrochloric acid - HCI. When hydrochloric acid is combined with water, it decomposes into a hydrogen ion (H+) and a chlorine ion (CI). Since the composition of the water molecule also contains hydrogen, the decomposition of hydrochloric acid total hydrogen ions in solution will increase.

And what happens to alkalis when they enter the water? In water, alkalis release hydroxide ions. For example, sodium hydroxide (NaOH) is an alkali. When combined with water, it decomposes into sodium ions (Na+) and hydroxide ions (OH). When hydroxide ions meet the hydrogen ions of water, the total amount of hydrogen ions in the solution is reduced.

What is a foundation?

A base is a compound chemically opposite to an acid. The composition of the base includes metal ions and associated hydroxide ions. These substances are able to attach hydrogen ions (H+) from an acid. When a base is mixed with an acid, it completely neutralizes its properties, and as a result of the reaction, a salt is formed.

For example, in terms of chemistry, the toothpaste you know well is a base that neutralizes the acid left in the mouth after eating.

REMEMBER! Due to the fact that ions exist only in solutions, acids also show their properties only in solutions.

What is alkali?

Alkalis are compounds that include a metal ion and a hydroxide ion (OH-). Chemists refer to alkalis as hydroxides of alkali and alkaline earth metals. Alkalis are white substances that dissolve well in water. Moreover, dissolution is always accompanied by a very active release of heat. Alkalis react with acids to form salt and water.

An alkali such as sodium hydroxide is used to make hard soap.

Alkalis are very active! They are able to absorb not only water vapor from the air, but also molecules of carbon dioxide, hydrogen sulfide, etc. Therefore, alkalis are stored in a very airtight container. Concentrated alkalis destroy glass, and sometimes even porcelain. If we compare alkalis with acids, then alkalis can cause more severe burns, as they penetrate tissue very quickly and are almost impossible to wash off with water.

Why are some liquids acids and others alkalis? It turns out that it's all about the type of ions. If the concentration of hydrogen ions is higher in the liquid, such a liquid is an acid, and if hydroxide ions, then an alkali.

The pH scale is used to measure the acidity or alkalinity of a solution from 0 to 14.

If the pH of the solution is in the range of 0-7, then such a solution is considered acidic, while a solution with pH = 0 is the most acidic. Solutions with a pH in the range of 7-14 are alkaline, while a solution with a pH = 14 is considered the most caustic and dangerous.

If the pH of the solution is 7, then such a solution is neutral, since the concentration of hydrogen ions is equal to the concentration of hydroxide ions. An example of a neutral solution is pure water.

What is a pH value?

Translated from the Latin pH (potentia hydrogeny) means "power of hydrogen", i.e. activity of hydrogen ions in an aqueous solution.

How do chemists determine the presence of water in a substance?

They take colorless copper sulfate (CuSO 4 ) and add it to the substance. If there is no water, then the powder remains colorless, however, even with a minimum amount of water, it turns blue.

Concentrated acids and alkalis

Poisonous liquids are not only found in school laboratories, they are all around us. These are various household chemicals (washing powders and stain removers), flower fertilizers and pesticides, varnishes and paints, adhesives and solvents, gasoline and diesel fuel, batteries, brakes and other technical fluids, and in the kitchen - vinegar and acetic acid.

It is clear that all the above substances must be used strictly for their intended purpose and in accordance with certain rules indicated on the label of each product. Unfortunately, non-compliance with safety measures when working with toxic agents can lead to serious health problems: poisoning, various damage to the skin and mucous membranes.

ATTENTION! Be sure to remember the following information: acids with a very low pH (less than 2) and alkalis with a pH above 13 are extremely dangerous!

You have already managed to make sure that around us there is a huge amount of acids and alkalis. Dairy products, vegetables and fruits contain citric, malic, oxalic, acetic, lactic, ascorbic and other acids. It's hard to believe, but the seeds of cherries and almonds contain (albeit in minimal amounts) such a strong poison as hydrocyanic acid! It is known that many insects prefer to defend themselves with different acids. Ever wondered why the bites of an ordinary tiny ant are so painful? And all because he sprays droplets of formic acid into the wound. Some types of caterpillars also secrete this acid, and tropical spiders and some beetles protect themselves from enemies with the help of acetic and sulfuric acids.

CAREFULLY! As a rule, concentrated acids and alkalis are available in all school non-tachchemistry rooms, and they can only be used under the guidance of a teacher.

The use of alkalis

Alkalis are widely used in various industries, medicine and everyday life. For example, caustic soda is used to dissolve fats and is included in many detergents, is used in the production of cellulose, oils, diesel fuel. Alkalis are also used to make soap, artificial fibers, various dyes, etc.

Acids in the soil

It turns out that there are acids in soils, and the ability of soil to exhibit the properties of acids is called acidity. This indicator depends on the presence of hydrogen ions in the earth. The growth and development of plants depend on the acidity of the soil. Most of them prefer neutral or close soils. However, there are a number of plants that thrive on acidic soils, such as rhododendrons, hydrangeas, and azaleas. Some varieties of hydrangeas can change the color of the buds depending on growing conditions and soil acidity. Scientists have found that the color of the buds is affected by the presence of aluminum!

Most garden soils are characterized by a sufficient content of this element. In an acidic environment, aluminum compounds become soluble and become available to plants, which is why buds grow. blue color. In a neutral or alkaline environment, aluminum is in the form of insoluble compounds, so it does not enter plants. As a result, pink buds grow on such soils.

Acids and alkalis in our body

To digest food, the body uses gastric juice, which includes hydrochloric acid and various enzymes. Sometimes, especially after overeating, we can feel pain in the stomach. Most often, to relieve discomfort, it is enough to take an antacid, or anti-acid, drug, the main action of which is aimed at neutralizing hydrochloric acid in the stomach. As a rule, all antacids are alkalis, and it is they that neutralize the increased activity of acids.

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 negative charge, in this case, these are OH ions -). Titles grounds consists of three parts: words hydroxide , to which the name of the metal is added (in 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- it's all the same stuff chemical formula which NaOH. Anhydrous sodium hydroxide- it's 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 produced different ways. For getting 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

CaO + H 2 O → Ca (OH) 2

But these methods have not been found in industry. practical value, of course, in addition to obtaining calcium hydroxide Ca(OH) 2 . Receipt sodium hydroxide and potassium hydroxide associated with the use of electricity. With electrolysis aqueous solution sodium or potassium chloride, hydrogen is released at the cathode, and chlorine at the anode, while in the solution where electrolysis occurs, it 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

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 (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 valences (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) possible as a result chemical reaction exchange between iron salt and alkali. For example

Fe 2 (SO 4) 3 + 6 NaOH → 3 Na 2 SO 4 +2 Fe (OH) 3

The word "acid" comes from the Latin word for "sour". Some foods on our table, like vinegar or lemon juice, are acids. A base is a compound that is chemically opposite to an acid, and when reacted with an acid, it gives a neutral compound -. Water-soluble bases are called alkalis. Citrus fruits - grapefruits, oranges, lemons - contain citric and ascorbic acids. Bee venom is an acid. You can neutralize it with a base. Citrus fruits - grapefruits, oranges, lemons - contain citric and ascorbic acids.

acids

Acids are compounds that contain and form hydrogen ions (H +) when dissolved in. Ions are particles with an electric charge (see the article ""). It is ions that give acids their properties, but they can only exist in solution. Consequently, the properties of acids appear exclusively in solutions. The sulfuric acid molecule (H 2 SO 4) consists of hydrogen, sulfur and oxygen. Hydrochloric acid (HCl) contains hydrogen and chlorine. An acid is considered strong if most of its molecules disintegrate in solution, releasing hydrogen ions. Hydrochloric, sulfuric, nitric acids are strong. The strength of an acid is measured by the pH number - pH indicator. Strong acids are very aggressive; once on the surface of an object or on the skin, they burn through it. Containers with strong acids are marked with the symbols accepted all over the world, meaning "dangerous" and "high activity".

Acids such as citric or acetic, i.e. produced by living organisms are called organic. Acids are widely used in the chemical and medical industries, in the production of food and synthetic fibers. Grape vinegar contains a weak acid called acetic acid. Tomatoes contain organic salicylic acid. The colored spots on the skin of sea snails contain an acid with an unpleasant taste that repels predators. All acids are characterized by similar behavior in. For example, when acids react with bases, a neutral compound is formed - salt and water. Reactions of acids with most give salt and hydrogen. Acids react with carbonates to form salts. carbon dioxide and water. Known to culinary experts, baking powder contains sodium bicarbonate and tartaric acid. When water is added to flour containing baking powder, the acid and carbonate of the powder react, carbon dioxide starts to bubble out and this helps the dough to rise.

Bases and alkalis

A base is a compound chemically opposite to an acid. An alkali is a base that is soluble in water. When mixed with an acid, the base neutralizes its properties, and the reaction product is a salt. Toothpaste is a base that neutralizes the acid left in the mouth after eating. Household liquid cleaners contain alkalis that dissolve dirt. Gastric tablets contain alkalis that neutralize the acid that circulates during indigestion. From the point of view of chemistry, bases are substances capable of attaching hydrogen ions (H +) from an acid. An oxide ion (O 2-) and a hydroxide ion (OH -) can combine with hydrogen ions in an acid. Hence, metal oxides, such as magnesium oxide, and metal hydroxides, such as sodium hydroxide (caustic soda), are bases. Sodium hydroxide (NaOH) consists of sodium, oxygen and hydrogen. Magnesium hydroxide (Mg (OH) 2) consists of magnesium, oxygen and hydrogen.

Many bases and alkalis are very caustic substances and therefore dangerous: they corrode living things. Liquid cleaners contain alkalis that dissolve dirt. In the paper industry, sodium hydroxide dissolves tree resin and frees the cellulose fibers from which paper is made. Sodium hydroxide (caustic soda) is used in cleaning fluids and (like potassium hydroxide) in soap making. Soap is a salt formed by the reaction of alkalis with acids of vegetable fats. The wasp's sting releases an alkali that can be neutralized with an acid such as vinegar.

pH and indicators

The strength of acids and bases is determined by the pH number. It is a measure of the concentration of hydrogen ions in a solution. The pH number varies from 0 to 14. The lower the pH, the higher the concentration of hydrogen ions. A solution with a pH less than 7 is an acid. Orange juice has a pH of 4, which means it's an acid. Substances with a pH = 7 are neutral, and substances with a pH greater than 7 are bases or alkalis. The pH of an acid or alkali can be determined using an indicator. An indicator is a substance that changes color when it comes into contact with an acid or base. So litmus turns red in acid and blue in alkali. Acid turns blue litmus paper red, and red litmus paper turns blue or purple in alkali. Litmus is obtained from primitive plants called lichens. Other plants such as hydrangea and red cabbage are also natural indicators.

The so-called universal indicator is a mixture of several colors. It changes color depending on the pH of the substance. It turns red, orange, or yellow in acids, green or yellow in neutral solutions, and blue or purple in alkalis.

Sulphuric acid

Sulfuric acid plays an important role in industry, primarily in the production of fertilizers based on superphosphates and ammonium sulfate. It is also used in the production of synthetic fibers, dyes, plastics, drugs, explosives, detergents, car batteries. Sulfuric acid was once called mineral acid, since it was obtained from sulfur - a substance found in the earth's crust in the form of a mineral. Sulfuric acid is very active and aggressive. When dissolved in water, it releases a lot of heat, so it must be poured into water, but not vice versa - then the acid will dissolve and the water will absorb heat. It is a powerful oxidizing agent, i.e. during oxidation reactions, it gives oxygen to other substances. Sulfuric acid is also a drying agent, i.e. takes in water bound to another substance. When sugar (C 12 H 22 O 11) is dissolved in concentrated sulfuric acid, the acid takes water from the sugar, and a foaming mass of black coal remains from the sugar.

Acids in the soil

The acidity of the soil depends on the nature of the rocks that formed it and on the plants growing on it. On chalk and limestone rocks, the soil is usually alkaline, while in meadows, in sandy and wooded areas, it is more acidic. acidity is also increased acid rain. For agriculture, neutral or slightly acidic soils are best suited, with a pH of 6.5 to 7. Decaying, dead leaves form organic humic acid and increase the acidity of the soil. Where soils are too acidic, crushed limestone or slaked lime (calcium hydroxide) is added to them, i.e. bases that neutralize soil acids. Plants such as rhododendrons and azaleas grow well in acidic soils. Hydrangea flowers are blue in acidic soil and pink in alkaline soil. Hydrangea is a natural indicator. Its flowers are blue in acidic soils and pink in alkaline soils.

Acid and alkali - eternal struggle opposites

Few people know, but the predominance of acid or alkali in the human body will depend on what diseases a person will be predisposed to. blood pH healthy person, according to the latest medical research, is 7.8, which indicates the predominance of alkali in the body. Such a person colds will bypass. Why? Yes, because colds and inflammatory processes are always an acidic environment. Bacteria - causative agents of colds can only multiply in an acidic environment, and once in an alkaline environment, they safely die. For example, laundry soap has been the number one enemy of all types of bacteria for many years and is used to "alkalize" the surface of the hands before eating. Or during a cold, we drink hot milk with honey - milk and honey are alkaline products, when they enter the body, they increase alkalinity and contribute to recovery. Tea with lemon is also an alkaline solution (especially if it is not sweetened), which is also used during a cold.

But what about acid, maybe we don’t need it at all? We need acid for healthy digestion. If a person's stomach does not have acid environment, then the process of digestion of food will turn into flour. Intestinal dysbacteriosis is the result of a violation of acidity in the stomach, which leads to serious digestive problems and is fraught with the development of chronic intestinal diseases.

So, we have found out that for health a person needs not only alkali, but also acid. Now let's consider the results of the predominance of acid and alkali in the body and the methods for eliminating such deviations. The main factor in the formation of the internal environment of a person is the diet. There are "acidic" foods, that is, those that increase the acidity of the body, and "alkaline" foods that increase the alkalinity of the internal environment of the body. Acidic foods include: meat and meat products, dairy products, fish, sugar, eggs, bakery products, beer. The human diet, constantly consisting of the above products, will eventually lead to a decrease in immunity and the development of chronic inflammatory diseases, such as bronchitis, pancreatitis, gastritis with high acidity, prostatitis, sinusitis, cystitis, pyelonephritis, and other diseases associated with inflammatory processes. Such a person often catches a cold, "all his drafts." The body is unable to cope with huge amount incoming lactic and other types of acids, it accumulates in the organs, and chronic inflammatory diseases begin to develop there. In men, the predominance of acid leads to infertility and impotence, since spermatozoa can only survive in an alkaline environment. Increased acidity of the body reduces the activity of livestock, which leads to male infertility, and subsequently to impotence. In women, increased acidity of the body also threatens the development of inflammatory processes, overweight and leads to infertility. In this case, the acidity of the vagina increases (in the normal state it is slightly acidic), and the spermatozoa, falling into the woman, die before they reach the uterus. And if sperm motility is reduced by the increased acidity of the male body, then conception is out of the question. Of course, the reason described is not the only reason why fertility in men and women is currently declining. Consider demographic issues modern Russia and the world as a whole is necessary in a complex, but to the question healthy eating nation should pay close attention.

However, if a person eats exclusively alkaline foods, and these include vegetables (fresh and in salads seasoned with vegetable oils), fruits, cereals, whole milk, honey, red and white dry wine, canned vegetables, then this leads to an excess of calcium in the body. and the development of diseases of the joints, the deposition of salts, which, in turn, can cause diseases of the cardiovascular system, urolithiasis, the appearance of stones in the liver, kidneys, gallbladder. As we can see, a balanced diet is necessary for human health.

To summarize: for human health, both animal products of “acidic” origin and vegetable origin must be present in the diet. Throughout the year, it is necessary to change the diet so that excess acid or alkali does not accumulate in the body. The daily menu of a person should change constantly, it is necessary to avoid constancy and maximalism in the diet. Constant consumption of the same foods leads to the development of chronic diseases.

In conclusion, I want to pay special attention to men who consider meat and meat products to be real “male” food. An excess of lactic acid, which is rich in meat, in the body of a man leads to infertility and impotence. Therefore, the next time, before declaring to his wife: “What am I, a rabbit, or something, to eat your carrot salad! Meat is the food of a real man!” - remember the fertility of the latter and that an exclusively meat diet is a direct path to infertility and impotence. If you want to be healthy - keep the acid-base balance.

And in the bath, and in the bath, always and everywhere - the eternal glory of water! Another way to keep good physical state are hardening procedures. Here is an example from the life of one of my patients. After he was helped to relieve acute phenomena in the hospital