Whether ions can coexist with each other depends on anything

1) Due to the metathesis reaction, ions cannot coexist in large quantities.

2) Due to the redox reaction, ions cannot coexist in large quantities.

See if they react with each other, such as generating precipitates and other things.

(3) There is weak electrolyte formation. For example, OH-, CH3CoO-, PO43-, HPO42-, H2PO4-, F-, CLO-, AlO2-, SiO32-, CN-, C17H35CoO-, etc. cannot coexist with H+ in large quantities; Some acidic weak acid groups such as HCO3-, HPO42-, HS-, H2PO4-, and HSO3- cannot coexist with OH- in large quantities; NH4+ cannot coexist with OH- in large quantities.

4) Some ions that are prone to hydrolysis are conditioned in solution. For example, AlO2-, S2-, CO32-, C6H5O-, etc. must exist in solution under alkaline conditions; For example, Fe3+, Al3+, etc. must exist in solution under acidic conditions. These two types of ions cannot exist in the same solution at the same time, that is, the "double hydrolysis" reaction can occur between the ions.

Such as 3alo2-+3al3++6h2o=4al(oh)3 and so on.

2 Due to the redox reaction, ions cannot coexist in large quantities.

1) Ions with strong reducing properties cannot coexist in large quantities with ions with strong oxidizing properties. For example, S2-, HS-, SO32-, I- and Fe3+ cannot coexist in large quantities.

2) It cannot coexist in large quantities in acidic or alkaline media due to redox reactions. For example, mno4-, cr2o7-, no3-, clo- and S2-, HS-, SO32-, HSO3-, I-, Fe2+, etc. cannot coexist in large quantities. SO32- and S2- can coexist under alkaline conditions, but cannot coexist under acidic conditions due to the occurrence of 2S2-+SO32-+6H+=3S +3H2O reaction. H+ and S2O32- cannot coexist in large quantities.

3. Hydrolyzable cations and hydrolyzable anions cannot coexist in large quantities in aqueous solution (double hydrolysis).

Examples: Al3+ and HCO3-, CO32-, HS-, S2-, AlO2-, CLO-, etc.; Fe3+ cannot coexist in large quantities with CO32-, HCO3-, AlO2-, Clo-, etc.

4 Ions that can undergo complexation reaction in the solution cannot coexist in large quantities.

For example, Fe2+, Fe3+ and SCN- cannot coexist in large quantities; Fe3+ cannot coexist in large quantities.

Methods for judging ion coexistence:

The so-called whether several ions can coexist in the same solution means that there is no reaction between the ions, and to solve this kind of problem, we must pay attention to the prerequisites in the title, which are summarized as follows:

1) Look at the question of the question, such as "can coexist in large quantities", "cannot coexist in large quantities", or "may coexist in large quantities", etc.

2) Clarify the qualifications of the question, such as:

If the color of the solution is limited, if the problem is colorless and transparent, there must be no Fe2+ (light green), Fe3+ (brownish-yellow), Cu2+ (blue), Mno4 (purple) and other ions; Also note that "transparent" is not "colorless".

Limit the acidity and alkalinity of the solution, a"In a strongly acidic (or pH 1) solution", that is, it contains a large amount of H+, H+ should be taken into account, and neither OH nor weak acid ions can coexist in large quantities.

b."In a strong alkaline (or pH 14) solution", that is, it contains a large amount of OH, OH should be taken into account, and H+ and weak alkali cations cannot coexist in large quantities.

c."In a solution ionized from water to C(H+) 1 10 10 mol l, or in a solution ionized from water to C(OH) 1 10 10 mol l", that is, a group of ions that can coexist in large quantities under acidic or alkaline conditions;

d."In a solution that reacts with Al to produce H2", in fact, in a solution under acidic or alkaline conditions (except nitric acid);

e."Solutions that can dissolve Al2O3 or Al(OH)3" are solutions that contain a large amount of H+ or Oh, in fact, in solutions under strong acid or alkaline conditions;

f."In neutral solution", ions that cannot exist in large quantities in neutral solutions, such as weak basic cations such as Al3+, Fe3+, Cu2+, etc., are essentially acidic, and they cannot exist in large quantities in neutral solutions; Weak acid anions such as clo, CO32, and PO43 are essentially to make the solution alkaline, and they cannot exist in large quantities in neutral solutions.

Define the type of reaction.

...... due to redox reactionsThat is, only the redox reactions between ions are considered;

Limit the ions already present in the solution.

If "Fe3+ and Cl are already present in the solution", then OH, SCN, and Ag+ ions cannot coexist in large quantities.

The condition for the coexistence of large amounts of ions is that there is no reaction between ions.

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

(1) Substances with strong oxidizing properties cannot coexist with substances with strong reducing properties;

Common particles with strong oxidizing properties: Mno4-, ClO-, Fe3+, No3- (when combined with H+, it has strong oxidizing properties).

Common particles with strong reducibility: Fe2+, SO32-, S2-, I-;

2) Substances that can be dihydrolyzed cannot coexist: such as:

Al3+ cannot coexist with the following particles: HCO3-, CO32-, AlO2-, ClO-, SiO32-, HS-, S2-

Fe3+ cannot coexist with the following particles: HCO3-, CO32-, AlO2-, ClO-, AlO2-, NH4+ cannot coexist with the following particles: AlO2-, SiO32-, etc.

3) Particles that can generate weak electrolytes cannot coexist, such as H+ and HCO3-, CO32-, NH4+ and OH-, CH3COO- and H+, etc.

4) Particles that can generate precipitates cannot coexist, such as CO32- and Ca2+, Fe3+ and Oh-, Fe2+ and Oh-, Ba2+ and SO42-, Ag+ and Cl-, etc.

Hopefully, this is the most common.

The so-called coexistence of several ions in the same solution in large quantities means that there is no reaction between the ions; If ions can react with each other, they cannot coexist in large quantities.

1.In the same solution, if any of the following conditions are met, an ionic reaction will occur, and the ions cannot be dissolved.

A large number of liquids coexist.

1) Formation of insoluble substances or microsolubles: such as Ba2 and CO32-, AG and Br-, Ca2 and SO42- and Oh-, OH- and Cu2, etc.

I can coexist in large quantities.

2) Formation of gases or volatile substances: such as NH4 and OH-, H and CO32-, HCO3-, S2-, HSO3-, SO32-, etc.

Quantity coexists. 3) Generate substances that are difficult to ionize: such as H and CO32-, S2-, SO32-, F-, Clo-, etc. to form weak acids; OH- and NH4, Cu2

and so on to generate a weak base; h With OH- to produce water, 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; MnO4- and Cl- cannot coexist in large quantities.

2.The law of application of additional implicit conditions:

1) When the solution is colorless and transparent, there must be no colored ions in the solution. Common colored ions are Cu2, Fe3, Fe2,

mno4- etc.

2) There are definitely no ions reacting with OH- in a strongly alkaline solution.

3) There are certainly no ions reacting with H+ in a strongly acidic solution.

In general, pay attention to the following:

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+), iron ions (Fe3+), 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.

There are some preparation materials to see whether redox reactions, precipitation, hydrolysis, acid-base neutralization, gas formation, and complexion reactions occur.