Chemical reaction precipitation, what is the precipitation reaction in chemistry

Soluble salt 1 + soluble salt 2 = new salt 1 new salt 2

Soluble salt + soluble base = new salt new base.

At least one of these three conditions must be present in the product for the reaction to proceed to the end, either precipitate, gas, or water.

Salt and salt reaction to form two other salts, to make the reaction occur, according to the definition of metathesis reaction, it can be known that there must be or water generation, soluble salt and soluble salt reaction must have a precipitate in the product.

Soluble salts and soluble bases react with a certain precipitate in the product?

nh4cl+naoh=nacl+nh3↑+h2o

Who said that what is required is that there must be a weak electrolyte, not necessarily precipitation.

Because the soluble salts in the solution are ionized into ions, only when a weak electrolyte is generated, the ions will change, and the reaction will be carried out, if not, all kinds of ions are in the solution, and they are not reacting.

Soluble salts and bases exist in the form of ions in solution, and if they react but do not generate a precipitate, there are still those ions in the solution, so a precipitate must be generated. When precipitation occurs, the ions do not exist in the solution, and it does not matter whether the reaction is or not (it can be understood in junior high school).

Don't be so rote memorizing, junior high school understands it for the time being.

For example, NH4Cl+NaOH==NH3·H2O+NaCl

These are not.

Not necessarily! But there must be one of the three of water, precipitation, and gas, or it is not called metathesis reaction!

It's hard to explain, it depends on how you usually feel when you do the question.

In the reaction of acid-base salt solution, if the product is insoluble in water, there will be precipitation.

The main precipitation is: calcium carbonate.

barium carbonate, barium sulfate, silver chloride, silver carbonate, rubber carbonate copper; Iron hydroxide, copper hydroxide, magnesium hydroxide, aluminum hydroxide, etc. If these substances are formed in the spinal solution, a precipitate is formed. In addition, calcium hydroxide, barium hydroxide solution with carbon dioxide.

The reaction also has a precipitate formation.

NaHSO4 excess, i.e., Ba(OH)2 in small amounts, Ba2+ and OH- remain 1:2. One Ba2+ requires one SO42- precipitate, and two Oh- requires two H+, so Ba2+ +2OH- +2H+ +SO42-===BaSO4 + 2H2O.

NaHSO4 is in small amounts, H+ and SO42- are kept at 1:1, one SO42- precipitates a BA2+, and one H+ can only neutralize one OH-, so H+ +SO42- +BA2+ +OH-===BAso4+H2O.

ba(oh)2 + h2so4 = baso4↓ +2h2o

Learning Method: The principle of systematization and structuring requires students to form a certain system of what they have learned in their minds and become an organic part of their overall knowledge, rather than being isolated and unrelated. Because only systematic and structured knowledge can be easily transformed into competence, and it is easy to apply and learn the scientific method of learning.

It is gradually formed on the basis of understanding and subjective initiative after the leap from perceptual cognition to rational cognition.

This is the further understanding and deepening of knowledge, and it is also a necessary process before applying knowledge in experiments. Therefore, in teaching and learning, it is necessary to organically link the formation of concepts with the systematization of knowledge, and strengthen the logical connections between the basic knowledge of chemistry in each part, as well as between chemistry and physics, mathematics and biology. Pay attention to the macro to the micro, with the guidance of theories such as the structure of matter, to reveal the inner nature of matter and its changes.

And in ordinary times, we should attach great importance to and do a good job in the systematic work of connecting the old and the new from the known to the unknown. Make the knowledge learned into a small system and a small structure, and then gradually become a large system and a large structure to meet the requirements of systematization and structure.

Ben was netizen.

Not necessarily. The premise of chemical change is the creation of new substances. When no new substance is formed, it is not a chemical change.

The key to precipitation depends on when it occurs, and it can also be a physical change, for example, when the brine solution is evaporated, when the solvent is burned to a certain extent, there will also be sodium chloride precipitation, which is also a kind of precipitation, but this is a physical change process.

Chemical change refers to the process of conversion or transfer of atoms or electrons between molecules in contact with each other to form new molecules accompanied by changes in energy, which is essentially the breaking of old bonds and the formation of new bonds.

Chemical changes are always accompanied by physical changes. In the process of chemical change, there are usually luminescence, exothermia, and endothermy. According to the atomic collision theory, the chemical change between molecules is accomplished through collision, and two conditions need to be met to complete the collision of the molecule that reacts

1) Have sufficient energy; (2) Correct orientation. Because the reaction needs to overcome a certain molecular energy barrier, it must have a higher energy to overcome the molecular energy barrier. Two colliding molecules must have the correct orientation for the old bond to break.

CuSO4+2NaOH=Cu(OH)2 +Na2SO4 blue precipitate generation, the upper part is a clear solution Mass conservation law experiment.

Ca(OH)2 + CO2 = CaCO3 + H2O Clarified lime water becomes turbid, apply CO2 inspection and lime mortar to paint the walls.

Ca(HCO3)2δ CaCO3 +H2O+CO2 white precipitation, produces gas that makes the clarified lime water turbid, scale formation. Formation of stalactites.

HCl+AGnO3= AGCL+HNO3 Produces white precipitate, insoluble in dilute nitric acid The principle of testing Cl—.

Ba(OH)2+ H2SO4=BASO4 +2H2O produces a white precipitate, insoluble in dilute nitric acid The principle of testing SO42—.

BaCl2 + H2SO4 = BaSO4 + 2HCl Generate white precipitate, insoluble in dilute nitric acid Test the principle of SO42-.

Ba(NO3)2+H2SO4=BASO4 +2HNO3 Generate white precipitate, insoluble in dilute nitric acid The principle of testing SO42—.

FeCl3+3NaOH = Fe(OH)3 +3NaCl solution fades yellow and has reddish-brown precipitate.

AlCl3+3NaOH = Al(OH)3 +3NaCl has a white precipitate to form.

mgcl2+2naoh = mg(oh)2↓+2nacl

CuCl2+2NaOH = Cu(OH)2 +2NaCl solution fades blue and has a blue precipitate.

CaO+ H2O = Ca(OH)2 white bulk solid becomes powder, quicklime to prepare lime slurry.

Ca(OH)2 + SO2=CASO3 + H2O has a white precipitate to generate in junior high school.

Ca(OH)2+Na2CO3=CaCO3 +2NaOH has a white precipitate to produce industrial caustic soda and a small amount of laboratory caustic soda.

Ba(OH)2+Na2CO3=BaCO3 +2NaOH has a white precipitate to form.

Ca(OH)2+K2CO3=CaCO3 +2koH has a white precipitate to form.

AgNO3+NaCl = AGCl +Na NO3 white precipitate insoluble in dilute nitric acid (similar reaction to other chlorides) It is used to test chloride ions in solutions.

BaCl2 + Na2SO4 = BaSo4 + 2NaCl white does not dissolve in the precipitate of dilute nitric acid (other sulfate-like reactions) It is used to detect sulfate ions.

CaCl2+Na2CO3= CaCO3 +2NaCl has a white precipitate to form.

MgCl2+Ba(OH)2=BaCl2+Mg(OH)2 is formed with a white precipitate.

Add the corresponding reagent to see if there is a reaction.