How to determine the equation corresponding to the neutralization reaction. Neutralization reaction, the essence of the method and practical application

Neutralization- a chemical reaction that occurs between two compounds that have the properties of an acid and a base. As a result of their interaction, the properties of both substances are lost, which leads to the release of salt and water.

Scope of neutralization

Calculations on this reaction are especially often used:

• in agrochemical laboratories;
• in chemical production;
• when handling waste.

The neutralization method is used in clinical laboratories to determine the buffer capacity of blood plasma, the acidity of gastric juice. It is also actively used in pharmacology, when it is necessary to carry out a quantitative analysis of inorganic and organic acids. This process can be carried out according to all correctly composed equations.

External manifestations of neutralization

The process of acid neutralization can be observed if, first, a few drops of an indicator are added to the solution, which will change the color of the solution. When alkali is added to this mixture, the color disappears completely. But it should be taken into account that the indicators change their color not strictly at the equivalent point, but with a deviation. Therefore, even with the correct choice of the indicator, an error is allowed. If it was chosen incorrectly, then all the results are distorted.

In the conditions of the school curriculum, citric acid and ammonia are used for this. As an example, consider the reaction process between hydrochloric acid and caustic soda. As a result of their interaction, a well-known solution of edible salt in water is formed. The following can also serve as indicators:

• methyl orange;
• litmus;
• methyl red;
• phenolphthalein.

It should be noted that the reverse reaction of neutralization is called hydrolysis. Its result is the formation of a weak acid or base.

When choosing a neutralizing agent, the following must be taken into account:

• industrial properties of the compound;
• availability;
• cost price.

Previously, magnesium oxide was used as a neutralizer. Now it is not popular because it has a high cost and reacts rather slowly.

Types of neutralization reactions

In the process of interaction of a strong base with the same strong acid, the reaction shifts towards the formation of water. However, this process does not reach the end, since salt hydrolysis begins.

When a weak acid is neutralized with a strong base, the reaction is reversible. As a rule, in such systems the course of the reaction is shifted towards the formation of salt, since water is a weaker electrolyte than, for example, hydrocyanic acid, acetic acid or ammonia.

The rate of the neutralization process varies depending on the specifics of the substances used. For example, when using NaOH, the required degree of acidity appears almost immediately. CaO leads to the desired reaction only after 15-20 minutes, and MgO - after 45 minutes. Moreover, in the last two cases, the strongest decrease in acidity is observed in the first 5 minutes after the neutralizing agent has been introduced. If the rate of the process is not very high, then secondary oxidation begins to slow it down even more.

Heat generation during the neutralization process

Often this happens under the influence of nitric acid. The higher the amount, the more heat is released. When salt is obtained, exposure to heat leads to undesirable consequences, since it begins to decompose with the release of chlorine. Due to the release of heat, it can be said that all neutralization reactions are exothermic. Its release occurs due to the difference between the total energy of H+ and OH- ions, as well as the energy of formation of water molecules.

Types of neutralization reactions. The reaction itself implies the extinguishing of foci (microbes, acids and toxins).

Neutralization reaction in medicine

The neutralization reaction is used in microbiology. This is based on the fact that some compounds are able to bind pathogens of various diseases, or their metabolisms. As a result, microorganisms are deprived of the opportunity to use their biological properties. This also includes the inhibition reactions of viruses.

Neutralization of toxins occurs according to a similar principle. Various antitoxins are used as the main component, which block the action of toxins, preventing them from showing their properties.

Neutralization reaction in inorganic chemistry

Neutralization reactions are one of the foundations of the inorganic. Neutralization refers to a type of exchange reaction. The reaction yields salt and water. Acids and bases are used for the reaction. Neutralization reactions are reversible and irreversible.

irreversible reactions

The reversibility of the reaction depends on the degree of dissociation of the constituents. If two strong compounds are used, then the neutralization reaction will not be able to return to the original substances. This can be seen, for example, in the reaction of potassium hydroxide with nitric acid:
KOH + HNO3 – KNO3 + H2O;

The neutralization reaction in a particular case turns into a salt hydrolysis reaction.

In ionic form, the reaction looks like this:
H(+) + OH(-) > H2O;

From this we can conclude that the reaction of a strong acid with a strong base cannot be reversible.

Reversible reactions

If the reaction occurs between a weak base and a strong acid, or a weak acid and a strong base, or between a weak acid and a weak base, then this process is reversible.

Reversibility occurs as a result of a shift to the right in the equilibrium system. The reversibility of the reaction can be seen when using as starting materials, for example, or hydrocyanic acid, as well as ammonia.

Weak acid and strong base:
HCN+KOH=KCN+H2O;

In ionic form:
HCN+OH(-)=CN(-)+H2O.

Weak base and

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 - the 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.

Lesson topic: "Neutralization reaction as an example of an exchange reaction"

The purpose of the lesson: to form an idea of ​​the neutralization reaction as a particular case of the exchange reaction.

Tasks:

Create conditions for the development of ideas about the neutralization reaction as a particular case of the exchange reaction;

To expand students' knowledge of the properties of acids and bases;

Continue developing the skills of compiling equations of chemical reactions;

To cultivate observation and attention during the demonstration experiment.

Lesson type : combined

Equipment and reagents : hydrochloric acid, solutions of sodium hydroxide, copper (II) hydroxide, phenolphthalein, test tubes.

During the classes

Organizing time.

Guys, let's continue our journey through the country called Chemistry. In the last lesson, we got acquainted with the city called Foundations and its inhabitants. The main inhabitants of this city are the foundations. Define the term "foundation". Well, now let's check how you did your homework.

Checking homework.

№ 7, 8.

Questioning and further updating of knowledge.

What classes of inorganic substances do you know?

Define the terms "oxides", "acids", "salts".

What substances does water react with?

What substances are formed when water reacts with basic and acidic oxides?

How to prove that acid is formed as a result of the interaction of water with an acidic oxide?

What are indicators?

What indicator are you talking about?

From alkali I am yellow, as in a fever,

I blush from acids, as from shame.

And I'm looking for saving moisture

So that Wednesday could not seize me.

(Methyl orange)

To get into acid is a failure for him,

But he will endure without a sigh or cry.

But in the alkalis of such a blond

Not life will begin, but solid raspberries.

(Phenolphthalein.)

What other indicators do you know?

Define the terms "acidic oxide", "basic oxide".

What groups are bases divided into?

What color is phenolphthalein, methyl orange, litmus in alkali solution?

Learning new material.

You already know that alkalis are soluble bases, when working with them, special rules of safe behavior must be observed, since they have a corrosive effect on our skin. But they can be "neutralized" by adding an acid solution to them - to neutralize. And the topic of today's lesson: "Neutralization reaction as an example of an exchange reaction" (recording the topic on the board and in a notebook).

The purpose of today's lesson: to form an idea of ​​\u200b\u200bthe neutralization reaction; learn to write the equations of neutralization reactions.

Let's remember what types of chemical reactions you already know. Define reaction data type

Na 2 O + H 2 O = 2 NaOH

2H 2 O = 2H 2 + O 2

Zn + 2HCl = ZnCl 2 +H 2

Define these types of reactions.

You also already know that if phenolphthalein is added to alkali, the solution will turn crimson. But if an acid is added to this solution, the color disappears (dem. interactionsNaOHandHCl). This is a neutralization reaction.

Write the equation on the board:NaOH + HCl=NaCl+H 2 O

The result is salt and water.

Let's all together try to define a neutralization reaction.

The neutralization reaction does not belong to any of the hitherto known types of reactions. This is an exchange reaction. General scheme of the exchange reaction: AB + CD = AD + CB

That is, it is a reaction between complex substances, during which they exchange their constituent parts.

And who knows what acid is in our stomach? Why do you think it is recommended for heartburn, if there is no pill at hand, to drink a little soda solution?

The fact is that a soda solution also has an alkaline environment, and when we drink this solution, a neutralization reaction occurs. A solution of soda neutralizes the hydrochloric acid found in our stomach.

Do you think insoluble bases react with acids? (Student answers). Dem. Cu(OH) interactions 2 and HCl .

Write the equation on the board:Cu(OH) 2 + 2 HCl = CuCl 2 + 2 H 2 O.

Anchoring

Add the following reaction equations:

a) KOH+ H 2 SO 4 = …;

b) Fe(OH) 2 + HCl=…;

in) Ca(OH) 2 + H 2 SO 4 =…. .

What initial substances must be taken to obtain the following salts by neutralization reaction:Ca( NO 3 ) 2 ; NaI; BaSO 4.

Substances given:HCl; H 2 SO 4 ; Fe( Oh) 3 . Write equations for all possible neutralization reactions between them.

Physical education: The teacher shows the substances, and the students need to determine which class of substances the substance belongs to and perform the following actions: oxide - hands up, salt - stand up, acid - hands to the sides, bases - do nothing.

Generalization

Complete the proposed scheme

Main classes of inorganic substances

SO 2 ; Na 2 Oh? ? ?

H 2 SO 4 ; HCl NaOH;Ca(OH) 2 CaCl 2; Na 2 SO 4

2. Complete the sentences below:

A group of OH atoms is called...

The valency of this group is constant and equal to ....

Bases are made up of atoms.... and one or more... .

The chemical properties of bases include their effect on .... At the same time, the indicators acquire color: litmus - ....; phenolphthalein - ....; methyl orange - ....

In addition, the bases react with .... .

This reaction is called...

The products of this reaction are... and …. .

An exchange reaction is a reaction between... substances, in which they exchange their ... parts.

The neutralization reaction is a special case of the reaction ....

VII Reflection

What did you learn in today's lesson? Have we reached the goals set in the lesson?

Homework: § 33 No. 6, prepare for practical work No. 6

Additional Information:Did you know that the women of Ancient Russia washed their hair with a solution of spruce ash or sunflower ash? The ash solution is soapy to the touch and is called "lye". Such a solution has an alkaline environment, like the substances that we study. Ash in Arabic is al-kali.

The historical names of the most important alkalis: sodium hydroxide - caustic soda, potassium hydroxide - caustic potash. Alkalis are used to make glass and soap.

Mystery:

It contains metal and oxygen,

Plus hydrogen.

And this combination

Call -….. (bottom)

Leonid Chueshkov

Ahead is always here "ash",

And what is left behind.

She stings and stings.

And at first glance it is simple,

And it's called - ... (acid)

Leonid Chueshkov

And water, for example:

Examples

Application

Neutralization underlies some of the most important methods of titrimetric analysis.

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