Describe the neutralization reaction. The specifics of the chemical neutralization process
The interaction of an acid and a base to form a salt and water is called a neutralization reaction. Typically, such reactions proceed with the release of heat.
general description
The essence of neutralization is that the acid and base, exchanging active parts, neutralize each other. As a result, a new substance (salt) and a neutral medium (water) are formed.
A simple and clear example of a neutralization reaction is the interaction of hydrochloric acid and sodium hydroxide:
HCl + NaOH → NaCl + H 2 O.
If you dip a litmus paper into a solution of hydrochloric acid and sodium hydroxide, then it will turn purple, i.e. will show a neutral reaction (red - acidic, blue - alkaline).
A solution of two active compounds turned into water due to the exchange of sodium and chlorine, so the ionic equation for this reaction is as follows:
H + + OH - → H 2 O.
After heating the resulting solution, the water will evaporate, and table salt - NaCl will remain in the test tube.
Rice. 1. Formation of salt after evaporation.
In such reactions, water is an essential product.
Examples
Neutralization reactions can occur between strong and weak acids and alkalis. Consider two types of reactions:
- irreversible reactions - formed salt does not decompose into constituent substances - acid and alkali (they flow in one direction);
- reversible reactions - the formed compounds are able to decompose into the original substances and interact again (flow in both directions).
An example of the first type of reaction is the interaction of a strong acid with a strong base:
- H 2 SO 4 + 2KOH → K 2 SO 4 + 2H 2 O;
- HNO 3 + KOH → KNO 3 + H 2 O.
Reversible reactions occur when a weak acid is neutralized with a strong base, as well as a weak base with a weak acid:
- H 2 SO 3 + 2NaOH ↔ Na 2 SO 3 + 2H 2 O;
- Fe (OH) 3 + H 3 PO 4 ↔ FePO 4 + 3H 2 O.
Weak insoluble or slightly soluble bases (Fe (OH) 3, Fe (OH) 2, Mg (OH) 2, Zn (OH) 2) are also neutralized by a strong acid. For example, copper hydroxide does not dissolve in water, but when interacting with nitric acid forms a salt (copper nitrate) and water:
Cu(OH) 2 + 2HNO 3 ↔ Cu(NO 3) 2 + 2H 2 O.
Rice. 2. Interaction of copper hydroxide with acid.
Neutralization reactions are exothermic, they proceed with the release of heat.
Usage
Neutralization reactions are the basis of titrimetric analysis or titration. This is a method for quantitative analysis of the concentration of substances. The method is used in medicine, for example, to determine the acidity of gastric juice, as well as in pharmacology.
Rice. 3. Titration.
In addition, the practical application of neutralization in the laboratory is important: if acid is spilled, it can be neutralized with alkali.
What have we learned?
The reaction in which an acid and a base form a salt and water is called neutralization. This reaction is possible between any acids and bases: a strong acid and a strong alkali, a weak acid and a weak base, a strong base and a weak acid, a weak base and a strong acid. The reaction proceeds with the release of heat. Neutralization is used in medicine and pharmacology.
The concept of “neutralization reaction” that exists in inorganic chemistry implies a chemical process in which substances with acidic and basic properties interact, as a result of which the participants in the reaction lose both those and other characteristic chemical properties. The neutralization reaction in microbiology has the same global significance; its products lose their biological properties. But, of course, this is a completely different process with different participants and outcomes. And the biological property in question, and which is primarily of interest to physicians and scientists, is the ability of a microorganism to cause disease or death in a susceptible animal.
Areas of use
Most often, this research method is used to identify viruses, that is, to diagnose viral infectious diseases. Moreover, the test can be aimed both at identifying the pathogen itself and antibodies to it.
In bacteriology, this technique is usually used to detect antibodies to bacterial enzymes, such as antistreptolysins, antistaphylolysins, antistreptokinases.
How is this test done?
The neutralization reaction is based on the ability of antibodies - special immune blood proteins - to neutralize antigens - foreign agents that enter the body. If it is necessary to detect the pathogen and identify it, then a standard immune serum containing antibodies is mixed with biological material. The resulting mixture is kept in a thermostat for the required time and introduced into a living susceptible system.
These are laboratory animals (rats, mice), chicken embryos, cell cultures. In the absence of a biological effect (illness or death of the animal), it can be concluded that this is exactly the virus for which the standard serum was used. Since, as already mentioned, a sign that the reaction has passed is the loss of bioproperties by the virus (the ability to cause the death of the animal) due to the interaction of serum antibodies and virus antigens. When determining toxic substances, the algorithm of actions is the same, but there are options.
If any substrate containing a toxin is examined, then it is mixed with standard serum. In the case of studying the latter, a control toxic substance is used. In order for the neutralization reaction to proceed, this mixture is also incubated for a predetermined time and injected into the susceptible system. The technique for evaluating the result is exactly the same.
In medical and veterinary practice, the virus neutralization reaction used as a diagnostic test is carried out in the so-called paired sera technique.
This is a way to confirm the diagnosis of a viral disease. For its implementation in a sick person or animal, they are taken twice - at the beginning of the disease and 14-21 days after that.
If, after the test, an increase in the number of antibodies to the virus by 4 or more times is detected, then the diagnosis can be considered confirmed.
The neutralization reaction is considered one of the most important for acids and bases. It is this interaction that suggests the formation of water as one of the reaction products.
Mechanism
Let us analyze the equation of the neutralization reaction using the example of the interaction of sodium hydroxide with hydrochloric (hydrochloric) acid. The hydrogen cations formed as a result of the dissociation of the acid bind to hydroxide ions, which are formed during the decomposition of alkali (sodium hydroxide). As a result, a neutralization reaction proceeds between them.
H+ + OH- → H 2 O
Characteristics of the chemical equivalent
Acid-base titration is related to neutralization. What is titration? This is a way to calculate the available mass of a base or acid. It involves measuring the amount of alkali or acid with a known concentration, which must be taken to completely neutralize the second reagent. Any neutralization reaction involves the use of such a term as "chemical equivalent".
For alkali, this is the amount of base that, in the case of complete neutralization, forms one mole of hydroxide ions. For an acid, the chemical equivalent is determined by the amount released during the neutralization of 1 mol of hydrogen cations.
The neutralization reaction proceeds in full if the initial mixture contains an equal number of chemical equivalents of the base and acid.
A gram equivalent is the mass of a base (acid) in grams that can form one mole of hydroxide ions (hydrogen cations). For a monobasic acid (nitric, hydrochloric), which, when a molecule decomposes into ions, releases one hydrogen cation each, the chemical equivalent is similar to the amount of the substance, and 1 gram equivalent corresponds to the molecular weight of the substance. For dibasic sulfuric acid, which forms two hydrogen cations during electrolytic dissociation, one mole corresponds to two equivalents. Therefore, in an acid-base interaction, its gram equivalent is equal to half the relative molecular weight. For a tribasic phosphoric acid, when completely dissociated, forming three hydrogen cations, one gram equivalent will be equal to one third of the relative molecular weight.
For bases, the principle of determination is similar: the gram equivalent depends on the valency of the metal. So, for alkali metals: sodium, lithium, potassium - the desired value coincides with the relative molecular weight. In the case of calculating the gram equivalent of calcium hydroxide, this value will be equal to half the relative molecular weight of slaked lime.
Mechanism explanation
Let's try to understand what a neutralization reaction is. Examples of such an interaction can be taken differently, let us dwell on the neutralization of nitric acid with barium hydroxide. Let's try to determine the mass of acid that the neutralization reaction needs. Examples of calculations are given below. The relative molecular weight of nitric acid is 63, and barium hydroxide is 86. We determine the number of gram equivalents of the base contained in 100 grams. Divide 100 g by 86 g / eq and get 1 equivalent of Ba (OH) 2. If we consider this problem through a chemical equation, then we can compose the interaction as follows:
2HNO 3 + Ba(OH) 2 → Ba(NO 3) 2 + 2H 2 O
The equation clearly shows all the chemistry. The neutralization reaction here proceeds completely when two moles of acid react with one mole of base.
Features of normal concentration
When talking about neutralization, the normal concentration of base or alkali is often used. What is this value? The normality of the solution demonstrates the number of equivalents of the desired substance that exists in one liter of its solution. With its help, quantitative calculations are carried out in analytical chemistry.
For example, if you want to determine the normality and molarity of a 0.5 liter solution obtained after dissolving 4 grams of sodium hydroxide in water, you first need to determine the relative molecular weight of sodium hydroxide. It will be 40, the molar mass will be 40 g / mol. Next, we determine the quantitative content in 4 grams of the substance, for this we divide the mass by the molar mass, that is, 4 g: 40 g / mol, we get 0.1 mol. Since the molar concentration is determined by the ratio of the number of moles of a substance to the total volume of the solution, the molarity of an alkali can be calculated. To do this, we divide 0.1 mol by 0.5 liters, as a result we get 0.2 mol / l, that is, 0.2 M alkali. Since the base is monoacid, its molarity is numerically equal to normal, that is, it corresponds to 0.2 n.
Conclusion
In inorganic and organic chemistry, the neutralization reaction between an acid and a base is of particular importance. Due to the complete neutralization of the initial components, an ion exchange reaction occurs, the completeness of which can be checked using indicators for an acidic and alkaline environment.
The lesson is devoted to the study of the reaction between substances opposite in properties - acids and bases. Such reactions are called neutralization reactions. During the lesson, you will learn how to use the formula of salt to make its name, and write down its formula according to the name of the salt.
Topic: Classes of inorganic substances
Lesson: Neutralization reaction
If you mix equal amounts of hydrochloric acid and sodium hydroxide, then a solution is formed in which the medium will be neutral, i.e. it will contain neither acid nor alkali. Let us write the equation for the reaction between hydrochloric acid and sodium hydroxide if the result is sodium chloride and water.
When 1 mol of hydrogen chloride (HCl) and 1 mol of sodium hydroxide (NaOH) react, 1 mol of sodium chloride (NaCl) and 1 mol of water (H 2 O) are formed. Please note that during this reaction, two complex substances exchange their constituents and two new complex substances are formed:
NaOH+HCl=NaCl+H 2 O
Reactions in which two compounds exchange their constituents are called exchange reactions.
A special case of an exchange reaction is a neutralization reaction.
A neutralization reaction is the interaction of an acid with a base.
Neutralization Reaction Scheme: BASE + ACID = SALT + WATER
Bases that are insoluble in water can also dissolve in acid solutions. As a result of these reactions, salts and water are formed. The reaction equation for the interaction of copper (II) hydroxide with sulfuric acid:
Cu (OH) 2 + H 2 SO 4 \u003d CuSO 4 + 2H 2 O
A substance with the chemical formula CuSO 4 belongs to the class of salts. We compiled the formula of this salt, knowing that the valency of copper in this process is II, and the valence of SO 4 is also II. But what is the name of this substance?
The name of the salt consists of two words: the first word is the name of the acid residue (these names are given in the table in the textbook, they must be learned), and the second word is the name of the metal. If the valency of the metal is variable, then it is indicated in brackets.
So, a substance with the chemical formula CuSO 4 is called copper (II) sulfate.
NaNO 3 - sodium nitrate;
K 3 PO 4 - potassium phosphate (orthophosphate).
And now, let's do the reverse task: we will make a formula for salt by its name. Let's make formulas of the following salts: sodium sulfate; magnesium carbonate; calcium nitrate.
In order to correctly compose the salt formula, we first write down the symbol of the metal and the formula of the acid residue, from above we indicate their valencies. Find the LCM of valency values. Dividing the LCM by each of the valency values, we find the number of metal atoms and the number of acid residues.
Please note that if the acid residue consists of a group of atoms, then when writing the salt formula, the acid residue formula is written in brackets, and the number of acid residues is indicated outside the bracket by the corresponding index.
1. Collection of tasks and exercises in chemistry: 8th grade: to textbook. P.A. Orzhekovsky and others. “Chemistry. Grade 8 / P.A. Orzhekovsky, N.A. Titov, F.F. Hegel. - M .: AST: Astrel, 2006. (p. 106)
2. Ushakova O.V. Chemistry workbook: 8th grade: to the textbook by P.A. Orzhekovsky and others. “Chemistry. Grade 8” / O.V. Ushakova, P.I. Bespalov, P.A. Orzhekovsky; under. ed. prof. P.A. Orzhekovsky - M .: AST: Astrel: Profizdat, 2006. (p. 107-108)
3. Chemistry. 8th grade. Proc. for general institutions / P.A. Orzhekovsky, L.M. Meshcheryakova, M.M. Shalashova. – M.: Astrel, 2013. (§33)
4. Chemistry: 8th grade: textbook. for general institutions / P.A. Orzhekovsky, L.M. Meshcheryakova, L.S. Pontak. M.: AST: Astrel, 2005. (§39)
5. Chemistry: inorg. chemistry: textbook. for 8 cells. general education institutions / G.E. Rudzitis, F.G. Feldman. - M .: Education, Moscow Textbooks OJSC, 2009. (§§31,32)
6. Encyclopedia for children. Volume 17. Chemistry / Chapter. ed. V.A. Volodin, leading. scientific ed. I. Leenson. – M.: Avanta+, 2003.
Additional web resources
2. Indicators in neutralization reactions. Titration().
Homework
1) with. 107-108 №№ 4,5,7 from the Workbook in Chemistry: 8th grade: to the textbook by P.A. Orzhekovsky and others. “Chemistry. Grade 8” / O.V. Ushakova, P.I. Bespalov, P.A. Orzhekovsky; under. ed. prof. P.A. Orzhekovsky - M.: AST: Astrel: Profizdat, 2006.
2) p.188 No. 1,4 from the textbook P.A. Orzhekovsky, L.M. Meshcheryakova, M.M. Shalashova "Chemistry: 8th grade", 2013
Page 2
Neutralization reactions involving a weak acid or a weak base do not proceed completely, only until equilibrium is established.
Neutralization reactions are exothermic processes (Н ОН-Н2О 57 3 kJ), therefore, hydrolysis of salts is endothermic.
Neutralization reactions are exothermic processes (H OH - H2O 57 3 kJ), therefore, hydrolysis of salts is endothermic.
A neutralization reaction is a chemical reaction between a substance that has the properties of an acid and a substance that has the properties of a base, which results in the loss of the characteristic properties of both compounds. The most typical neutralization reaction in aqueous solutions occurs between hydrated hydrogen ions and hydroxyl ions contained in strong acids and bases, respectively: H OH-H2O.
The neutralization reaction proceeds not only in aqueous, but also in non-aqueous solutions. The chemical nature of the non-aqueous solvent affects the state of the ions in solution and the degree of dissociation. The same substance can be a salt in one solvent, an acid in another, and a base in a third.
The neutralization reaction is accompanied by the release of heat; therefore, the Beckmann thermometer is preliminarily set in such a way that at the beginning of the experiment, the mercury in the thermometer capillary is at the bottom of the scale. After the calorimeter is assembled, its constant is determined (see previous work) by inserting an empty ampoule into the lid of the calorimeter.
Neutralization reactions proceed with the release of heat. However, the amount of heat released by mixing dilute acids and bases is difficult to estimate by touch. Concentrated acids and bases should never be mixed with each other. This mixture becomes so hot that it begins to boil and splash violently.
Neutralization reactions play a decisive role in spinning, as they predetermine the kinetics of deposition and the structure of the resulting filament. In addition, as a result of the neutralization reaction, a number of products pass into an unstable form and decompose.
The alkali neutralization reaction of naphthenic acids and phenols is reversible. Naphthenates and phenolates are hydrolyzed in the presence of water, forming the initial products. The degree of hydrolysis depends on the process conditions. It increases with an increase in temperature and decreases with an increase in the concentration of the alkali solution. Alkaline cleaning is advisable to carry out at low temperatures, using concentrated solutions.
Neutralization reactions occurring in aqueous solutions are similar to those occurring in non-aqueous media.
The neutralization reaction is an ion exchange reaction and takes place instantly. In contrast, the esterification reaction is not ion-exchange and proceeds more slowly. Both the ethylate formation reaction and the esterification reaction are reversible and, therefore, limited by the state of equilibrium.
