Chemistry experts do a favor about metathesis reactions

Middle School Requirements: Water or Gas or Precipitation.

High School Requirements: Weak electrolytes or gases or precipitation.

Concentration of ions: The electrolyte dissolves in water and ionizes ions.

For example, HCL produces H ions and Cl ions, and NaCl ionization produces Na ions and Cl ions.

Some substances are completely ionized (strong electrolytes, such as most salts, strong acids and strong bases), and some are incompletely ionized (weak, such as weak acids and weak bases).

Some cannot be ionized (non-electrolytes, such as organic matter), the preceding them are compounds, and the others are not electrolytes.

Then the essence of the metathesis reaction is a directional reaction with a small concentration of phase ions.

Specifically, it's about finding a way to reduce the number of ions.

So precipitation, gas is well understood.

Then because water (weak electrolyte) exists in a large amount in the molecular form of water, the ion concentration is also small.

I can reflect it, too. If it can't be reversed, it should be understood, and if it is reversed, there are more ions, and the original forward reaction will not occur.

Well, having said so much, I have to say one thing:

In junior high school, this question is not discussed, even if you know it, it will not help you at all for the high school entrance examination (it is compulsory in high school).

Just remember that metathesis reactions occur when water or gas or precipitation is generated!

Ions combine into precipitated or difficult to ionize substances or gases, so the concentration decreases rapidly, such as adding hydrochloric acid to sodium carbonate, CO32- and H+ combine into CO2 and H2O, CO2 overflows, H2O does not ionize, so carbonate and hydrogen ions no longer exist, that is, their concentrations decrease rapidly and irreversibly.

In the middle school range, this question is not discussed, irreversible means that the raw substance will no longer become reactants, the reactants react completely, as for the ion concentration, it involves a lot of high school knowledge, you can understand it as equivalent to the solute mass fraction.

The metathesis reaction is actually the exchange of ions, which is difficult to ionize, how can the ion be ionized if it cannot be ionized?

So the reaction is irreversible.

When the solution is mixed, the resulting refractory substances or precipitates are more stable. (ions cannot move freely) on the 1st floor, 1 sodium carbonate and hydrochloric acid react to form sodium bicarbonate and sodium chloride, and then 2 sodium bicarbonate reacts with hydrochloric acid to form sodium chloride and water.

Hydrochloric acid reacts in the case of very little 1, and if there is more, the 2nd type occurs).

Metathesis reaction concept: A reaction in which two compounds exchange components with each other to form two other compounds.

Metathesis reaction is one of the four basic types of reaction in chemistry. The reaction between liquids is generally formed by the exchange of components between two compounds, that is, the compounds participating in the metathesis reaction are ionized and dissociated into free-moving ions in the aqueous solution, and the ions are recombined into new compounds. Therefore, the reaction between acid, alkali and salt solutions is generally a metathesis reaction.

In inorganic chemistry, there are few metathesis reactions that are both metathesis or bucket reactions and redox reactions, and metathesis reactions that do not consider valency changes in middle school. Here is an example of a chemical reaction that is both a metathesis reaction and a redox reaction. Magnesium silicide and hydrochloric acid reaction [Mg2Si + 4HCl = 2 mgCl2 + SiH4] (SiH4, silane, where Si is +4 valence, H is -1 valence).

Summary of metathesis reaction: shirt swim grinding

Metathesis is a reaction in which two compounds exchange components with each other to form two other compounds. Its essence is that two compounds are interchangeable in solution, i.e., cations are exchanged at the same time or anions are exchanged at the same time. It can be abbreviated as ab+cd=ad+cb

The essence of the metathesis reaction is that the ions in the solution are combined into substances (such as water), insoluble substances (such as precipitation) or volatile gases, so that the metathesis reaction tends to be completed. In order to accurately determine the occurrence of metathesis reactions, it is necessary to memorize the solubility tables of common acids, alkalis, and salts, and use the solubility of substances correctly.

The understanding of metathesis reactions must grasp the two key words of "two compounds" and "exchange of components" in the concept. The reaction between acid, alkali and salt solutions is generally formed by the exchange of components between two compounds, that is, the compounds participating in the reaction are ionized in the aqueous solution to form free-moving ions, and the ions are recombined into new compounds, so the reaction between acid, alkali and salt solutions is generally a metathesis reaction.

The metathesis reaction is a reaction in which two compounds exchange components with each other to produce two other compounds.

The essence of the metathesis reaction is that the two substances that undergo the metathesis reaction exchange ions in the aqueous solution, and combine into substances that are difficult to ionize - precipitation, gas or weak electrolyte (most commonly water), so that the ion concentration in the solution decreases, and the chemical reaction proceeds in the direction of the reduction of ion concentration.

It can be abbreviated as ab+cd=ad+cb

Basic conditions: The two substances in which the metathesis reaction takes place can exchange ions in an aqueous solution and combine to form a substance that is difficult to ionize (precipitate, gas or weak electrolyte).

1. Basic oxide + acid: the acidity of the acid is strong (such as HCl, H2SO4, HNO3, etc.), and the reaction can occur.

2. Acid + alkali (neutralization reaction): when the acid and alkali are weak, no reaction occurs.

3. Acid + salt: strong acid to weak acid; There is precipitation after the exchange of ions; strong acids react with carbonates; A reaction can occur when one condition is met.

4. Alkali + salt: strong alkali reacts with ammonium salt; Both reactants are soluble, and there are one of three after the exchange of ions: precipitation, water, and gas; A reaction can occur when one condition is met.

5. Salt + salt: both reactants are soluble, and there is one of the three of precipitation, water and gas after the exchange of ions, and the reaction can occur if one condition is met.

Definition of metathesis reaction: The reaction in which two compounds exchange components with each other to produce two other compounds is called metathesis reaction.

The reaction in which two compounds exchange components with each other to form two other compounds is called metathesis.

It can be abbreviated as ab+cd=ad+cb

The essence of the metathesis reaction is that the ions in the solution combine into substances that are difficult to ionize (such as water), insoluble substances or volatile gases, so that the metathesis reaction tends to be completed.

In order to correctly write the chemical equation of the metathesis reaction, it is necessary to memorize the solubility tables of common acids, bases, and salts, and use the solubility of substances correctly.