What reactions between ions should be paid attention to in ionic reactions in chemistry detailed ex

There are many ion reactions.

It is the formation of salts such as precipitation, gases, acids and bases, oxygen and weak electrolytes.

Precipitation, there is a table at the back of the chemistry book, which salts are soluble and which salts are insoluble, just memorize it, pay special attention to the black precipitate of copper sulfide that is insoluble in sulfuric acid (the only reaction of strong acid to weak acid in high school).

Gases, mainly carbon dioxide (carbonate or bicarbonate acidic, special attention here is paid to the fact that bicarbonate reacts with alkali to form carbonate, so any condition seen in bicarbonate and acid or base can be ruled out), sulfur dioxide (sulfite acidic), hydrogen sulfide (sulfur ion acidic), chlorine (chloride ion hypochlorous acid acidity), nitric oxide (divalent iron and nitrate acidic), hydrogen bromide, hydrogen iodide (volatile), ammonia (not actually ammonia, Generally, ammonium and hydroxide meet, and the main thing obtained is ammonia monohydrate, and ammonia is obtained by heating), and the gas is mainly these.

Oxygen also, ferric can oxidize iodine ions can not oxidize bromine ions, nitrate only has oxidation under acidic conditions, hypochlorite regardless of acid or alkali has oxidation, can oxidize divalent iron, sulfur ions or something, sulfur ions have reducibility, sulfur ions and sulfite reactions occur under acidity, and do not react under alkaline. There should be a little bit of oxygen, but I can't remember it.

The only salt in high school that was a weak electrolyte was lead sulfate, but I never encountered this in the ion category.

More upstairs, aluminum ions can no longer exist under alkaline conditions, in fact, all the simple ions corresponding to weak bases cannot exist under alkaline conditions. There is also a double hydrolysis reaction of weakly acidic acids such as carbonate and sulfite, which needs to be noted.

Note that it is impossible to produce a reducing gas such as hydrogen in an acidic solution containing nitrate, and there is a very classic topic related to this, but I forgot about this topic.

Because I don't know if it's the third year of junior high school or high school, I hit some randomly, I don't know if it's helpful, some of the content may be wrong, I haven't read these for a long time, everything depends on your teacher.

H+ with carbonic heel, bicarbonate.

Aluminum ions and hydroxides.

In the reactionReactions in which ions are involved or ion-generatedThis is called an ionic reaction. In secondary school, which is limited to reactions that are carried out in solution, it can be said that ionic reactions refer to a class of reactions in which electrolytes are involved in aqueous solutions. Because the reaction of the electrolyte in the aqueous solution is the reaction of the ions ionized by the electrolyte in the aqueous solution.

Not necessarily! Ionic reactions generally refer to chemical reactions involving strong electrolytes (substances that can be completely ionized in an aqueous solution).

For example: sodium carbonate.

and dilute hydrochloric acid. co3

h+==CO2 (gas).

H2O metathesis reaction.

If the reactants are all weak electrolytes, it cannot be called an ionic reaction!

Such as: acetic acid. Reaction with copper hydroxide, 2CH3COOH+CU(OH)2===CH3COO)2Cu+2H2O

Acetic acid and copper hydroxide are both weak electrolytes and cannot be completely ionized, so it is mainly their molecular interactions!

The essence of an ionic reaction is a change in the concentration of certain ions. Common ionic reactions are mostly carried out in aqueous solutions. A chemical reaction with the participation of ions.

According to the reaction principle, ionic reaction can be divided into four types: metathesis, salt hydrolysis, redox and complexation. It can also be divided into interional, ion-to-molecule, and ion-atom reactions according to the particles participating in the reaction.

If the ions can reduce the chaos of the mixed solution, then they can react with each other. Or if the ions can reduce the total system energy, then they can react with each other. Or if the total concentration of ions can be reduced, then there can be a reaction between them, otherwise there is no reaction.

At the secondary level, the types of ionic reactions that are often considered are:

1. Metathesis reaction between ions (generation of precipitates, gases, and refractory ionization substances) 2. Redox reaction between ions.

3. The ions promote each other to carry out a complete double hydrolysis reaction.

4. Complexation reaction between ions.

If none of these conditions are met, then the reaction between these ions will not take place.

The reaction between ions does not occur because the conditions required for the reaction to occur between the ions are not met 1, the conditions for the metathesis reaction are not met, that is, there are no insoluble substances, difficult ionizations, and volatile substances 2, and the conditions for redox reactions are not met, that is, there is no reducing ion and oxidizing ion in the presence or only one condition.

3. It does not meet the conditions of double hydrolysis.

For an ionic reaction to occur, it must meet the requirements of precipitation, water or gas formation, and as long as one of the three is generated, an ionic reaction can occur, which is a necessary condition for the occurrence of an ionic reaction. Some ionic reactions cannot take place simply because the product does not have these three substances.

The reason why many chemical reactions are divided into excess and small amounts of substances is because these reactions can be carried out in two steps, and there are many examples, I will cite two examples, and you can figure it out for yourself.

Like the reaction of Na2CO3 and HCl, you know, the order of addition of this reaction is from Na2CO3 to HCL or HCL to Na2CO3 The reaction phenomenon is also different.

When HCl is added by Na2CO3, the reaction immediately releases bubbles, and the reaction equation is .

na2co3+2hcl=nacl+h2o+co2.

When Na2CO3 is added by HCl, the reaction is first non-phenomenal, and then bubbles are released, in fact, the equation of this reaction is also as follows.

na2co3+2hcl=nacl+h2o+co2.

But the difference is that this reaction can be step-by-step.

Step 1: Na2CO3+HCl=NaHCO3+NaCl, and there is no obvious phenomenon in the reaction.

Step 2: NaHCO3 + NaCl = NaCl + H2O + CO2, the reaction releases bubbles.

You see, there is a problem of excess and not too much of this reaction, if the HCL is not too much, the reaction will only go to the first step, if the HCl is added too much, the reaction can continue to the second step.

In another reaction, carbon dioxide is passed into the clarified lime water.

When the carbon dioxide is not excessive, CO2 + Ca(OH)2 = CaCO3 + H2O, the reaction clear solution becomes turbid, and a white precipitate is generated.

When carbon dioxide is continued to be introduced to an excess, CaCO3+CO2+H2O=Ca(HCO3)2, the reaction turbidity solution becomes clear again.

Do you see it?

Answer] B Answer Analysis] Test Question Analysis: Ion reaction is a reaction in which ions participate in or are generated, and the condition for the reaction is that the electrolyte (must be a compound and a pure substance) must ionize the ions that can react under certain conditions, so the sum is correct. The metathesis reaction has no elemental involvement, and it is wrong.

The ionic reaction between the acid-base salts does not involve oxides, which is wrong. Acidic oxides or alkaline oxides react with water to form the corresponding acids or bases, which are not involved in the reaction of salts, which is wrong.

Test Center: Ionic reactions.