Why is it necessary to have a precipitate or gas or water in the products of a metathesis reaction?

Because only precipitation or gas or water is generated, metathesis reactions.

will happen, otherwise the two substances do not react.

The metathesis reaction is a reaction in which two compounds exchange components with each other to produce two other compounds. The essence of metathesis reaction is: two substances that undergo metathesis reaction exchange ions in 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 is reduced, and the chemical reaction is carried out.

That is, in the direction of decreasing ion concentration. It can be abbreviated as ab+cd=ad+cb.

Metathesis reactions are the four basic types of reactions in chemistry.

One. To understand it, it is necessary to grasp the two key words of "compound" and "exchange of components" in the concept. The reaction between acid, alkali and salt solution 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 reactions that are both metathesis and redox reactions.

, valency is not considered at the secondary school level.

Variation of metathesis reaction, Mg2Si + 4HCl = 2mgCl2 + SiH4 (silane gas).

Basic oxides.

Acid: Acids are more acidic (such as HCl, H2SO4, HNO3, etc.) and can react.

Acid + base (neutralization reaction): When both acid and base are weak, no reaction occurs.

Acid + Salt: Strong acid.

weak acid production; There is precipitation after the exchange of ions; strong acids react with carbonates; A reaction can occur when one condition is met.

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.

Salt + salt: Both reactants are soluble and precipitate after exchanging ions.

Acid + metal oxide — salt + water, which belongs to metathesis reaction. For example: cao+2HCl==caCl2+H2O

Alkali + non-metallic oxide — salt + water, does not belong to the metathesis reaction. For example: CO2+2NaOH==NA2CO3+H2O

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 combine into substances that are difficult to ionize (such as water), insoluble substances (such as precipitation) or volatile gases, so that the metathesis reaction tends to be completed.

Because this is the condition for the metathesis reaction.

Summary. Hello, glad to your question, when the metathesis reaction occurs, the precipitate formed by the metathesis reaction is more difficult to dissolve than the precipitate generated by the hydrolysis reaction, and the metathesis occurs between the substances. When the metathesis reaction occurs to form a precipitate that is more difficult to dissolve than the precipitate generated by the hydrolysis reaction, a metathesis reaction occurs between the substances, such as the mixing of Na2S solution and CuSo4 solution, and the reaction formula is S2 + Cu2 + Cus.

When metathesis occurs, the precipitate formed by the metathesis reaction is more difficult than the precipitate generated by the hydrolysis reaction, and metathesis occurs between soluble substances.

Hello, glad to your question, when the metathesis reaction occurs, the precipitate formed by the metathesis reaction is more difficult to dissolve than the precipitate generated by the hydrolysis reaction, and the metathesis occurs between the substances. When the metathesis reaction occurs to form a precipitate that is more difficult to dissolve than the precipitate generated by the hydrolysis reaction, a metathesis reaction occurs between the substances, such as the mixing of Na2S solution and CuSo4 solution, and the reaction formula is S2 + Cu2 + Cus.

Hahahaha.

(1) CO2+H2O is equivalent to carbonic acid!

2) Carbonic acid is greater than hypochlorous acid!

3) Nacio + H2CO3 ==> salt and acid react to form new salt new acid!

4) The new acid HCIO is a very weak acid that is difficult to ionize and does not react with NaHCO3!

5) The water generated by metathesis reaction is also a substance that is difficult to ionize!

You don't have to know why, just like 1+1 doesn't need to know why it equals 2, of course, if you have to do it, it's just

The reaction in which two compounds exchange components with each other to form two other compounds is called metathesis. Its essence is: the two substances that undergo metathesis reaction exchange ions with each other in the aqueous solution, and combine into substances that are difficult to ionize--- precipitation, gas, and water, so that the ion concentration in the solution is reduced, and the chemical reaction is carried out in the direction of the reduction of ion concentration.

It can be abbreviated as ab+cd=ad+cb. The essence of the metathesis reaction is that the ions in the solution combine into ionized substances (such as water), insoluble substances or volatile gases, so that the metathesis reaction tends to be completed.

In metathesis reactions, there are roughly three ways in which the concentration of ions in the solution can be reduced

1) In the reaction, substances with very little solubility (precipitation) are generated;

2) There is gas released in the reaction;

3) Weak electrolytes (including water, weak acids, weak bases, etc.) are formed in the reaction. This is the condition under which the metathesis reaction can occur. As long as one of these conditions is met, the reaction can take place.

The metathesis reaction is ion exchange, if there is no water or gas or precipitation formation, can ions still be exchanged?

Because the essence of the metathesis reaction is the exchange of ions and the formation of new substances, only by generating water or gas or precipitation can we judge that the two substances have reacted.

Not necessarily. The key to the metabolization hundred reaction is the exchange of ions.

To understand metathesis reactions, it is necessary to first understand the dissociation of acid-base salts in solution. For example, sodium chloride solution essentially contains chloride ions and sodium ions. There are four ions in the mixed solution of sodium chloride and potassium nitrate, which is exactly the same as the mixed solution of potassium chloride and sodium nitrate.

When two compounds are dissolved in water, they are dissociated into two ions, and if they can be exchanged to form substances (water, gas, precipitate) that are difficult to dissociate in water, then the metathesis reaction occurs.

In the reaction seen in junior high school, if it is a reaction between alkali and salt, salt and salt, it generally does not produce water and gas, but only precipitate, so it is required that the reactants be dissolved in water first and become a solution. That is, the reactants are required to be soluble.

For example, sodium carbonate and barium sulfate do not react to form barium carbonate precipitate and sodium sulfate. You may try to write down the chemical equation, and you will find that the reverse reaction of the reaction can be carried out without considering the solubility of the reactants, and then it will change back to the original substance.

Of course, there are exceptions, alkali and ammonium salts can produce ammonia and water, which can react.

So I think that if the metathesis reaction can produce water and gas, the reaction can take place; Such as acid and alkaline oxide, acid and alkali reaction, etc.

If only the precipitate is generated internally, then the reactants are also required to be soluble.

The second answer above is worth reading, but he just didn't make it clear. This is a special case. If two compounds have the same ions, they generally do not react. After exchanging ions, it is the same as the original substance. This has nothing to do with physical change at all.

No, for example, the reaction between carbon dioxide and calcium hydroxide has precipitation and water formation, but it is not a metathesis reaction.

If two compounds exchange components with each other to form two other compounds, and there is water, gas, and precipitation (one can be satisfied). Then he must be a metathesis reaction.

No. The essence of the metathesis reaction is the formation of substances that are difficult to ionize, so that the ion concentration is biased to one side, and the reaction cannot be carried out if it is not generated. (The so-called precipitation refers to low solubility, if the saturated solution of sodium nitrate and potassium chloride is reacted at a temperature of 80 degrees, sodium chloride crystals will be precipitated, and it can be regarded as precipitation).

No, first of all, we have to see if this reaction is a chemical reaction, and the essence of a chemical reaction is the formation of new substances. A chemical reaction can only be said to have occurred if the resulting substance is completely different from the original substance (i.e., the chemical formula is different).

Not necessarily. For example.

Potassium chlorate. Heating.

Oxygen production. 2kclo3

2kCl3O2 has gas.

However, it does not belong to metathesis reactions. Wait a minute.

H2O2+CO does not react, so not necessarily, there must be an exchange of ions, and if it is not a molecule composed of root ions, the metathesis reaction will not occur.

These phenomena must be present in order to tell that a reaction has occurred. Without observable phenomena, it is impossible to tell whether a reaction has occurred or not.

Metathesis reaction is a reaction in which two compounds exchange components with each other to generate two other compounds, the essence of which is that the two compounds that undergo metathesis reaction exchange ions in aqueous solution and combine into precipitate, gas or weak electrolyte (most commonly water) that is difficult to ionize, so that the ion concentration in the solution is reduced, and the chemical reaction is carried out in the direction of the reduction of ion concentration.

From a macro point of view, there are specific conditions for whether a reaction can occur. In the case of the product, the exchange of components between the two compounds must contain water, gas, or precipitation in the other two compounds, which is a macroscopic phenomenon that can be observed. The formation of precipitate, gas, or water indicates a decrease in the concentration of ions in the solution and the reaction proceeds in the forward direction.

That is, the presence of precipitation, gas, or water (which can only be judged) can be observed to prove that the reaction actually occurred.

When it comes to high school knowledge about the movement of chemical equilibrium, when gas, precipitation, water, etc. are formed, the reaction moves in that direction.

Of course not! Metathesis reaction in junior high school chemistry refers to the reaction in which two compounds exchange components with each other to form two other compounds, which is called metathesis reaction. Metathesis reaction does not necessarily occur between two compounds, but can occur when one of the three types of gas, water or precipitate in the product is satisfied.

Therefore, the metathesis reaction does not necessarily have a precipitate formation.

The second sentence is also incorrect, there is a precipitate to produce metathesis is not necessarily a metathesis reaction, for example, the reaction of carbon dioxide and calcium hydroxide solution can produce a white precipitate, but the reaction is not a metathesis reaction.

In addition, the metathesis reaction actually has requirements for reactants.