Hydrochloric acid and alkali. Distinctive features of alkali. Basic properties of acids

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 will increase the total number of hydrogen ions in the solution.

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 alkalis are compared to acids, 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 obvious 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 part of many detergents, 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 blue buds grow. 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.

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 binary 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 territories 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 that ranges from 0-14 and indicates 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.

Alkalis are caustic, solid and easily soluble bases. Acids are generally acidic liquids.

Definition

acids- complex substances that include hydrogen atoms and acid residues.

alkalis- complex substances, which contain hydroxyl groups and alkali metals.

Comparison

Alkalis and acids are antipodes. Acids create an acidic environment, while alkalis create an alkaline environment. They enter into a neutralization reaction, as a result of which water is formed, and the pH environment from acidic and alkaline is converted to neutral.

Acids have a sour taste, while alkalis have a soapy taste. Acids, dissolving in water, form hydrogen ions, which determine their properties. All acids have similar behavior when they enter into chemical reactions.

Alkalis, when dissolved, form hydroxide ions, endowing them with characteristic properties. Alkalis attract hydrogen ions from acids. Alkalis have characteristic features that appear during chemical reactions.

The strength of alkalis and acids is determined by pH. Solutions with a pH less than 7 are acids, and solutions with a pH greater than 7 are alkalis. Alkalis and acids are distinguished using indicators - substances that change color when in contact with them. For example, litmus turns blue in alkalis and red in acids.

For greater reliability of the experiment, another indicator is added to alkalis - colorless phenolphthalein. It colors alkalis in a characteristic crimson color, and remains unchanged with acids. Traditionally, alkalis are determined precisely by phenolphthalein.

At home, acid and alkali are recognized by resorting to a simple experiment. Liquids are added to the baking soda and the reaction is observed. If the reaction is accompanied by the rapid release of gas bubbles, then the flask contains acid. Alkali with soda, which by its nature is the same alkali, does not react.

Findings site

1. Acids and alkalis are unable to peacefully coexist even for one second, being in contact. Having mixed up, they instantly begin a violent interaction. The chemical reaction with them is accompanied by hissing and warming up and lasts until these ardent antagonists destroy each other.
2. Acids tend to form an acidic environment, and alkalis tend to form an alkaline one.
3. Chemists distinguish an alkali from an acid by its behavior with litmus paper or phenolphthalein.

Acid and alkali - the eternal struggle of 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. The pH of the blood of a 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 enemy number one for 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 does not have an acidic environment in the stomach, then the process of digesting food will turn into flour. Intestinal dysbacteriosis is the result of a violation of acidity in the stomach, which entails 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. A 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 does not have time to cope with the huge amount of 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. It is necessary to consider the demographic problems of modern Russia and the world as a whole in a complex, but close attention should be paid to the issue of healthy nutrition of the nation.

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 joint diseases, salt deposition, which, in turn, can cause diseases of the cardiovascular system, urolithiasis, the appearance of stones in the liver, kidneys, and 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 maintain a good physical condition are tempering procedures. Here is an example from the life of one of my patients. After he was helped to relieve acute phenomena in the hospital