Why is there a double hydrolysis reaction with the participation of water, water does not appear in

It's simple, you can write it with water first, and then you can do it with water all the time....At the end, add the two equations and you'll discover the secret: if there's water on both sides of the equation, it's gone! And here's what's even more interesting:

Why is it so coincidental? Haha, thinking about it like this will enhance your interest in chemistry, each subject has its own interesting, looking forward to your discovery, exploration and progress!

You can write about the hydrolysis reaction with water. Write it step by step, and then combine it into a large hydrolysis equation. Square.

The water molecules on both sides of the process can be eliminated.

3(HCO3-)+Al3+)=3CO2 +Al(OH)3 Al2S3+3H2O=2Al(OH)3 +3H2S Aln+3H2O=Al(OH)3 +NH3 Al3+ with HCO3, CO32, HS-, S2-, ClO-, AlO2-; Fe3+ with HCO3, CO32, CLO-, ALO2-; Fe2+ vs. AlO2-; NH4+ with SIO32-, etc. In fact, since the solubility of Al(OH)3 and Fe(OH)3 is very small, the acid group of the acid, which is slightly stronger than carbonic acid, can also undergo a "double hydrolysis reaction" with Fe3+ and Al3+1. [Aluminum ion and bicarbonate ion] Al3++3HCO3-=AL(OH)3 +3CO2 2, [Aluminum ion and carbonate ion] 2Al3++3CO32-+3H2O=2Al(OH)3 +3CO2 3, [Aluminum ion and sulfide ion] 2Al3++3S2-+6H20=2Al(OH)3 +3H2S 4, [Aluminum ion and Hs- (Hydrogen thio) ion] Al3++3Hs-+3H2O=AL(OH)3+3H2S 5, [Iron ion and Tetrahydroxy Aluminate Ion] Fe3++3(Al(OH)4)-=Fe(OH)3+3Al(OH)3 6, [Iron Ion and Carbonate Ion] 2Fe3++3(CO3)2-+3H2O=2Fe(OH)3+3CO2 7, [Ammonium Ion and Tetrahydroxy Aluminate Ion] NH4++(Al(OH)4)-=NH3·H2O+Al(OH)3 8, [Iron Ion and Bicarbonate Ion] Fe3++3HCO3-=Fe(OH)3+3CO2 (because there is water in both the reactant and the product is offset, it is not represented).

1. [Aluminum ion and bicarbonate.

Ion] Al3+ 3HCO3-= Al(OH)3 3CO2 2, [Aluminum ion and carbonate.

Ion] 2Al3+ 3CO32- 3H2O = 2Al(OH)3 2CO2

3. [Aluminum ion and sulfur ion].

2Al3+ 3S2- 6H20=2Al(OH)3 3H2S 4, [aluminum ion and Hs- (thiobisin) ion].

Al3+ 3Hs- 3H2O=Al(OH)3 3H2S 5, [Iron ions.

and tetrahydroxyalaluminate ions].

Fe3+ 3(Al(OH)4)-=Fe(OH)3 3AL(OH)3 6, [Iron ion and Sozen carbonate ion].

2Fe3+ 3(CO3)2-+3H2O=2Fe(OH)3 2CO2 7, [Ammonium ion.

and tetrahydroxyalaluminate ions].

NH4+ (Al(OH)4)-=NH3·H2O AL(OH)3 8, [Iron and carbonic acid early hydrogen ions].

Fe3+ 3HCO3-=Fe(OH)3 3CO2 (because there is water in both the reactant and the product to cancel it out, it is not represented).

The big plus sign is the plus sign, and the small plus sign is the ion symbol! If I'm not mistaken, Fe(OH)3 is supposed to be colloidal. ）

In the case of complete hydrolysis, there is usually gas or precipitation in the hydrolysate products, resulting in irreversible hydrolysis reactions.

The double hydrolysis is that the two ions that make up the salt can be hydrolyzed, but not necessarily irreversible, such as the double hydrolysis of the ammonium carbonate of Liang Lao, but not completely hydrolyzed.

Completely hydrolyzed, it can be considered as special in double hydrolysis.

such as Al3+ and HCO-, until a complete reaction. Aluminum ions and bicarbonate do not necessarily undergo complete dihydrolysis, as long as the reaction conditions are slightly controlled, aluminum ions and bicarbonate can react to form basic alumina carbonate.

3(HCO3-)+Al3+)=3CO2 +Al(OH)3 Al2S3+3H2O=2Al(OH)3 +3H2S Aln+3H2O=Al(OH)3 +NH3 Al3+ with HCO3, CO32, HS-, S2-, ClO-, AlO2-; Fe3+ with HCO3, CO32, CLO-, ALO2-; Fe2+ vs. AlO2-; NH4+ with SIO32-, etc. In fact, since the solubility of Al(OH)3 and Fe(OH)3 is very small, the acid group of the acid, which is slightly stronger than carbonic acid, can also undergo a "double hydrolysis reaction" with Fe3+ and Al3+1. [Aluminum ion and bicarbonate ion] Al3++3HCO3-=AL(OH)3 +3CO2 2, [Aluminum ion and carbonate ion] 2Al3++3CO32-+3H2O=2Al(OH)3 +3CO2 3, [Aluminum ion and sulfide ion] 2Al3++3S2-+6H20=2Al(OH)3 +3H2S 4, [Aluminum ion and Hs- (Hydrogen thio) ion] Al3++3Hs-+3H2O=AL(OH)3+3H2S 5, [Iron ion and Tetrahydroxy Aluminate Ion] Fe3++3(Al(OH)4)-=Fe(OH)3+3Al(OH)3 6, [Iron Ion and Carbonate Ion] 2Fe3++3(CO3)2-+3H2O=2Fe(OH)3+3CO2 7, [Ammonium Ion and Tetrahydroxy Aluminate Ion] NH4++(Al(OH)4)-=NH3·H2O+Al(OH)3 8, [Iron Ion and Bicarbonate Ion] Fe3++3HCO3-=Fe(OH)3+3CO2 (because there is water in both the reactant and the product is offset, it is not represented).

fe2(so4)3 +3na2co3 +3h2o = 2fe(oh)3↓+3na2so4 +3co2↑

al2(so4)3 +3na2co3 +3h2o = 2al(oh)3↓+3na2so4 +3co2↑

2fecl3 +3na2co3 +3h2o = 2fe(oh)3↓+6nacl +3co2↑

2alcl3 +3na2co3 +3h2o = 2al(oh)3↓+6nacl +3co2↑

3(hco3-)+al3+)=3co2↑ +al（oh）3↓

al2s3+3h2o=2al（oh）3↓ +3h2s↑

Aln+3H2O=Al(OH)3 +NH3 is easily balanced using conservation of atoms and conservation of charge.

First of all, let's analyze why Al3+ and HCO3 can have a "double hydrolysis reaction" in aqueous solution, but Mg2+ and CO32 or HCO3 cannot have a "double hydrolysis reaction"? Because the solubility of Al(OH)3 is very small and H2CO3 is unstable and easy to decompose, the hydrolysate generated can be separated from the reaction system, and the hydrolysis reaction continues to the right according to the principle of equilibrium movement until the reaction is completely carried out, which can generally be popularly understood as "heaven (gas) into the ground (precipitation)"; However, the solubility of Mg(OH)2 is larger than that of AL(OH)3, and it is not easy to break away from the reaction system, so the hydrolysis reaction will reach equilibrium to a certain extent, and the hydrolysis reaction cannot be carried out completely. It is not difficult to see from the above:

The separation of the resulting hydrolysate from the reaction system is an important reason why the reaction can be carried out completely. Therefore, one of the conditions for the occurrence of the "double hydrolysis reaction" is that the hydrolysate is a very small solubility substance that is easy to detach from the reaction system

Al(OH)3, Fe(OH)3 or H2, O2 and other extremely insoluble gases. Of course, if the degree of hydrolysis is very large, the hydrolysis reaction can also be considered complete. Such as:

NH4)2S is almost hydrolyzed into NH3·H2O and Hs-.

In summary, whether the dihydrolysis reaction can be fully carried out depends on two factors:1Promote each other's degree of hydrolysis (including the influence of material nature, external conditions, etc.) 2Solubility of hydrolysate.

First of all, let's analyze why Al3+ and HCO3 can have a "double hydrolysis reaction" in aqueous solution, but Mg2+ and CO32 or HCO3 cannot have a "double hydrolysis reaction"? Because the solubility of Al(OH)3 is very small and H2CO3 is unstable and easy to decompose, that is, the generated hydrolysate can be separated from the reaction system, and according to the principle of equilibrium movement, the hydrolysis reaction continues to the right until the reaction is completeHowever, the solubility of Mg(OH)2 is larger than that of AL(OH)3, and it is not easy to break away from the reaction system, so the hydrolysis reaction will reach equilibrium to a certain extent, and the hydrolysis reaction cannot be carried out completely.

From the above, it is not difficult to see that the separation of the generated hydrolysate from the reaction system is an important reason for the complete progress of the reaction. Therefore, one of the conditions for the "double hydrolysis reaction" to occur is:

Hydrolysates are substances with very low solubility that are easy to detach from the reaction system, such as: Al(OH)3, Fe(OH)3 or extremely insoluble gases such as H2 and O2. Of course, if the degree of hydrolysis is very large, the hydrolysis reaction can also be considered complete.

There will be no reactants in complete double hydrolysis, and it is enough to detect whether there are residual reactants in the product, if not, the hydrolysis is complete, and vice versa.

The common ion pairs that can undergo "double hydrolysis reaction" in middle school chemistry are: Al3+ and HCO3, CO32, HS-, S2-;Fe3+ and HCO3, CO32;NH4+ with SIO32-, etc.

It can be based on the hydrolysis intensity of the two.

1.The organic part of the hydrolysis reaction is the reaction of water and another compound, the compound is decomposed into two parts, the hydrogen ions in the water are added to one of them, and the hydroxyl group is added to the other part, so as to obtain the reaction process of two or more new compounds, the inorganic part is the reaction of weak acid or weak base ions and water to generate weak acid and hydroxide ions or weak bases and hydrogen ions, and the hydrolysis of organic matter is more used in industry, mainly producing alcohol and phenol.

2.The hydrolysis reaction is the reverse reaction of the neutralization or esterification reaction.

3.The hydrolysis of most organic compounds is difficult to carry out smoothly with water alone, generally under alkaline or acidic conditions.