Summary knowledge points of chemical ion coexistence in the third junior high school

Hydrogen ions do not coexist with hydroxide ions.

Carbonate ions do not coexist with bicarbonate ions.

Copper ions, iron ions, magnesium ions, aluminum ions, and ammonium do not coexist.

Carbonate does not coexist with hydrogen ions, calcium ions with barium ions.

Chloride ions do not coexist with silver ions, sulfate ions with barium ions.

I'm going to take the high school entrance examination tomorrow, and now I'm happy to read books, and I hope you benefit from my efforts, thank you.

Hydrogen ion and hydroxide ion, hydrogen ion and carbonate ion, ammonium ion and hydroxide ion, barium ion and sulfate ion, silver ion and chloride ion, calcium ion and carbonate ion, etc.

1. Acid-base neutralization, H and OH ions cannot coexist.

2 Gases are generated, and H and CO3 ions cannot coexist.

3 Generate precipitate, the two ions that generate precipitate cannot coexist, such as CO3 and Ca ions can not coexist, and CaCO3 precipitate is generated.

4 Redox.

1. Acid-base neutralization.

2 Generate gas.

3 Generate precipitation.

4 Redox.

In the case of 2 and 3, the more difficult problem is the problem of double hydrolysis.

Carbonate – hydrogen, calcium, barium.

Bicarbonate --- hydrogen.

Sulfate --- barium.

Chlorine --- silver.

Hydroxide --- remove potassium, sodium, calcium, barium,

It's not too difficult to memorize the acid-base salt solubility table.

The coexistence of ions is essentially a matter of whether there is a reaction between ions. If the reaction occurs in solution, it cannot coexist. To see whether the stool wide-open reaction can occur, not only because of precipitation, gas, water, and difficult ionization of substances, but also because the solution is acidic, alkaline, colorless, colorless, and whether the redox reaction can be carried out.

1) There is gas generated. For example, CO32-, SO32-, S2-, HCO3-, HSO3-, HS-, HS-, etc., volatile weak acid acids cannot coexist with H+ in large quantities.

2) There is precipitation generation. For example, BA2+, Ca2+, Mg2+, Ag+, etc. cannot coexist with SO42-, CO32-, etc.; Mg2+, Fe2+, Ag+, Al3+, Zn2+, Cu2+, Fe3+, etc. cannot coexist with OH- in large quantities; Pb2+ and Cl-, Fe2+ and S2-, Ca2+ and Po43-, Ag+ and I- cannot coexist in large quantities.

Definition. The ion reaction is carried out in the direction of ion weakening, and ion coexistence essentially refers to whether ions can have a chemical reaction, and if ions cannot react with each other, they can coexist. Conversely, if ions in a solution can react with each other, they cannot coexist.

There are many factors that need to be considered for the reaction between ions, such as: whether volatile substances are formed between ions in the solution, whether insoluble substances are formed, whether weak electrolytes are generated, etc.

Can generate precipitates, microsolutes, gases, two or more of water can not coexist, other basically can, 4, redox, precipitation, gas, 1, the conditions for the coexistence of ions:

Interaction between two ionsIf a substance such as water, gas, or precipitate is formed, the two ions cannot coexist in the same solution.

Common non-coexisting ions in junior high school chemistry are as follows:

1）h++oh-→h2o ；（2）h++co32-→co2↑；（3）nh4++oh-→nh3↑；

4）ba2++so42-→baso4 ↓（5）ag++cl-→agcl ↓；

6）ca2++co32-→.1. First of all, if the ions in the solution want to coexist, they must not react with each other.

The conditions under which the metathesis reaction takes place, that is, the exchange of anions and cations between two compounds to form two new compounds - the reaction product must be formed by one of the precipitates, gases, and water. It can be seen that if the ions contained in the solution can form one of the above three substances, they cannot coexist.

I don't know if you get it. Let me give you a few examples.

If in the solution of sodium carbonate [Na2CO3]: it is obvious that Na+ and CO3- are one of the precipitated gases that cannot be formed. If.

1. In a strong acidic solution, it is not possible to shout that there are weak acid ions in the rotation: such as carbonate (CO3 2), bicarbonate (HCO3), sulfur ion (S2), thiohydrogen ion (HS), sulfite ion (SO3 2), silicate ion (SiO3 2), metaaluminate ion (ALO2), fluoride ion (F), etc., nor can there be a large amount of hydroxide (OH).

In a strong alkaline solution, there should be no weak alkali metal ions in large quantities. Such as: magnesium ion (Mg2+), ferrous ion (Fe2+), iron ion (Fe3+), aluminum ion (.

0, the common ones in junior high school are H+ and OH-Ca2+ and CO32- Ba2+ and SO4, 2-AG+ and Cl- Cu2+ and OH-Fe3+ and OH-Fe2+ and OH-Ba2+ and CO32-To judge whether it can be reflected, it depends on whether these two ions can react Can not coexist If you can't react, you can coexist If you can't react, you should remember the following sentences to determine whether the ions in the junior high school stage coexist potassium, sodium, ammonium and nitrate are soluble in water, (potassium salt, sodium salt, ammonium salt, nitrate can be soluble in water, and these four ions can coexist with other ions in water and dissolve in water. 0,

1) Read the solubility table after reading the book and remember the insoluble or slightly soluble substances. If two ions produce these things, they can't coexist. For example, calcium ions and carbonate ions.

2) If gas is generated, it cannot coexist. The most typical liquid spring in junior high school should be hydrogen ions, carbonate, and sulfite.

3) Produce water. For example, hydrogen ions and hydroxides.

4) If it is said in the stem that the solution is colorless, then the colored ions cannot exist. For example, copper ions, iron ions.

In other words, this should be all there is to junior high school, metathesis is still relatively simple redox reaction and the like, that is, oxidizing ions and reducing ions cannot coexist; In addition, there is a double hydrolysis or something (because it should not be rough is the content of junior high school.、So don't talk about it.、If you're interested, you can search for it yourself)., 2, there is a table at the back of the book, which talks about what ions and what ions together produce precipitates, gases.

Just put up with that back stool.

There is also a mantra that potassium, sodium, and nitric acid are soluble or something, give you a **, and it is more specific over there.

For chemistry at the junior high level, just look at whether water, gas, or solids are formed in the product. If there is, it cannot coexist; If not, they can coexist. Personal insights, I hope it will be useful to you. ,0,ions cannot coexist,0,

Hello landlord! Let's talk about them one by one.

Trivalent iron] First of all, trivalent iron cannot coexist with fluoride ions: Fe3+

6F-[FeF6]3-, the reaction equilibrium constant of this reaction. k

10 16 It is also one of the methods often used in analytical chemistry to mask iron ions, since complexes are formed, they naturally cannot coexist.

Ammonium root seems to be able to coexist, after all, there is such a thing as ammonium fluoride......The above analytical chemistry is often used to mask iron ions, that is, ammonium fluoride, but there is no absolute, after all, think about ammonium fluoride seems to be made of hydrogen fluoride and ammonia neutralization, and hydrogen fluoride and ammonia are both gases, think about it is unstable, and it is true: ammonium fluoride is thermally unstable, and solid ammonium fluoride will decompose into ammonia and hydrogen fluoride (NH4F) after heating

NH3HF), and in hot water, it will decompose into ammonia and ammonium bifluoride (2NH4F

nh3nh4hf2）。However, it is relatively stable at room temperature, so fluoride ions and ammonium can coexist at low temperatures, but not at high temperatures, depending on the temperature of the environment.

nitrate] this ......Still doesn't seem to react......However, under the catalysis of concentrated sulfuric acid, these two things can still react to produce nitrate fluoride.

NO2F,But,High school is not a reaction.,The landlord just knows.,It's okay to deal with it when you don't react when you take the exam.。

Copper ion] This is tricky, and it should not have been learned in high school to ......However, fluoride ions and copper ions really cannot coexist......First of all, fluoride ions and copper ions can be combined to form copper fluoride, which is a microsoluble substance, which naturally cannot be considered to coexist; Secondly, copper fluoride can also be combined with fluoride ions to form [CuF3], Cuf4]2 and [CuF6]4

Complexes and other complexes cannot coexist, so they .........

Well, that's it, if the landlord has a question, ask again!

1) Read the solubility table after reading the book and remember the insoluble or slightly soluble substances. If two ions produce these things, they can't coexist. For example, calcium ions and carbonate ions.

2) If gas is generated, it cannot coexist. The most typical in junior high school should be hydrogen ions, carbonates, and sulfites.

3) Produce water. For example, hydrogen ions and hydroxides.

4) If it is said in the stem that the solution is colorless, then the colored ions cannot exist. For example, copper ions, iron ions.

In other words, this should be all there is to junior high school, metathesis is still relatively simple redox reaction and the like, that is, oxidizing ions and reducing ions cannot coexist; In addition, there is a double hydrolysis or something (because it shouldn't be the content of junior high school.、So don't talk about it.、If you're interested, you can search for it yourself.。

As long as ions and ions cannot be combined into water, cannot be combined into gas, and cannot be combined into precipitation, they can coexist!

The combined into water are: hydrogen ions and hydroxide ions;

The main gases that are combined are: carbonate ions;

The combination of precipitation should be judged according to the solubility table at the back of the next textbook!

In a strong acidic solution, there can be a large number of weak acid ions: such as carbonate (CO32), bicarbonate (HCO3), sulfur ion (S2), hydroxide ion (HS), sulfite ion (SO32), silicate ion (SiO32), metaaluminate ion (ALO2), fluoride ion (F), etc., nor can there be a large number of hydroxide (OH). In a strong alkaline solution, there should be no weak alkali metal ions in large quantities.

For example, magnesium ions (Mg2+), ferrous ions (Fe2+), aluminum ions (Al3+), copper ions (Cu2+) and ammonium ions (NH4+), etc., can not exist in large quantities of hydrogen ions (H+) and acid root ions: HCO3, HSO3, HS, H2PO4, etc.

Ions that can undergo redox reactions cannot coexist: e.g., Fe3+ and I, Cu2+ and I, H+Fe2+ and No3, H+ and SO32, Clo and S2, Clo and Fe2+, H+, I and NO3, H+, I and SO32 or S2, etc.

Those that can form complex ions cannot coexist: such as: Fe3+ and SCN, AG+ and SO32, Fe3+ and C6H5O, etc.

1) Formation of insoluble substances or microsolubles: Ba2+ and CO32, Ag+ and Br, Ca2+ and SO42 cannot coexist in large quantities. (2) Formation of gases or volatile substances

For example, NH4+ and OH, H+ and CO32, HCO3, SO32, OH, HSO3, etc. cannot coexist in large quantities. (3) Generate substances that are difficult to ionize: such as H+ and CH3COO (i.e., acetate ions), CO32, S2-, SO32, etc., to form weak acids; OH and NH4+, Cu2+, Fe3+, etc. form weak bases; H+ and OH form water, and these ions cannot coexist in large quantities.

4) Redox reaction: oxidizing ions (such as Fe3+, NO3, CLO, Mno4, etc.) and reducing ions (such as S2, I, Fe2+, SO32, etc.) cannot coexist in large quantities. Note that Fe2+ and Fe3+ can coexist.

5) Formation of complexes: For example, Fe3+ reacts with SCN- to form complexes and cannot coexist in large quantities.

1) When the solution is colorless and transparent, there must be no colored ions in the solution. (2) There are definitely no ions that react with OH in a strong alkaline solution! (3) There are definitely no ions that react with H+ in a strongly acidic solution!

4) Ions can coexist in large quantities, including ions that do not have chemical reactions with each other, do not generate precipitation, and do not generate gas volatilization.

Answer: In the third year of chemistry, whether ions can coexist is mainly judged from the following points:

1. Whether there is gas generated. For example, hydrogen ions and carbonate ions produce carbon dioxide gas.

2. Whether water is generated. For example, hydrogen ions and hydroxide ions produce water.

3. Whether there is precipitation. For example, barium ions and sulfate ions produce barium sulfate precipitation.

Junior high school mainly involves the above aspects.

However, whether they can coexist in the future depends on the following points:

1. Whether there is metathesis reaction (weak electrolyte: weak acid, weak alkali, water, precipitation, gas production);

2. Whether there is a redox reaction;

3. Whether there is a complexation reaction;

The main point is whether there is a new substance. As long as new substances are created, they cannot coexist.

Hope it helps.