How do you determine the direction of a chemical reaction equation? Urgent!!! For example, the direc

This reaction is a metathesis reaction, after the reaction, the product should have water or gas or solid precipitation, from this point of view, BaSo4 is a precipitation, so the reaction is BaCl2 + H2SO4 = 2HCl + BaSO4, and this reaction is also a reaction of strong acid and weak acid. Hope it helps.

The direction of the equation is to go in the direction of instability, such as the formation of precipitates or weak electrolytes or the direction of low energy (spontaneous reactions), and this equation BACl2+H2SO4==2HCl+BaSO4 has precipitation formation, so proceed in this direction.

It depends on the direction of the reaction, and it is generally judged whether there is precipitation, gas, and water generation.

Like this question, barium sulfate is precipitated, so it reacts.

The conditions under which the displacement reaction can occur are the production of gas, precipitation or water. There is also the production of strong acids into weak acids, and the precipitation is converted into a more insoluble precipitation. In the solution, you can assume that the reaction occurs and push out the product, but if the product can react, it is incorrect, if it does not react, it is correct.

If 2HCl+Baso4 reacts, it will form BACL2+H2SO4, and the product will also react (because this reaction forms a precipitate), so 2HCl+BaSO4 does not react, and BACL2+H2SO4 reacts.

Baso4 is a precipitation, the first if the reaction will produce BACL2 and sulfuric acid, the reaction has precipitation and strong acids to form stronger acids and soluble substances, which is impossible. The second, on the contrary, produces a more stable precipitate and a relatively weak acid. The reaction can be established.

There are 4 criteria.

Chemical potential. The chemical potential change is less than 0

Electrode potential The potential difference is greater than 0

Gibbs free energy.

Gibbs free energy is less than 0

Entropy criterion The entropy change is greater than 0

Chemical reaction. "Direction" is the spontaneous direction of the chemical reaction (referred to as the "reaction direction"), that is, under certain conditions, without the help of external force, the direction in which the early reaction is automatically carried out, and the processes that occur in nature have a Li key directionality.

For example, water always flows automatically from high to low, not in the opposite direction. Another example:

When two objects with different temperatures come into contact with each other, heat automatically transfers from the hot object to the lower temperature object until the temperature of the two objects is equal. In terms of chemical changes, if the zinc flakes are placed in dilute sulfuric acid.

zinc flakes will automatically dissolve and hydrogen gas will be generated.

These processes that can proceed spontaneously without the action of external forces are called spontaneous processes (chemical processes are called spontaneous reactions).

H2SO4+BACL2=2HCl+BaSO4 precipitate group good symbol.

Therefore, the history of the laughter ion square collapsed lead Cheng for.

SO42-+BA=BASO4 precipitation symbol.

1. Buried CO2 into the two solutions, the precipitation is Ca(OH)2CO2 + Ca(OH)2 ==CaCO3 (precipitation) + H2O 2, Na2CO3 is added to the two solutions respectively, the gas is HCl, and the precipitation is produced by Ca(OH)2Na2CO3 + 2HCl===2NaCl + H2O + CO2 (gas) Ca(OH)2 + Na2CO3 =

2naoh + h2so4===na2so4 + 2h2o

naoh + hcl===nacl + h2o

Ba(OH)2 + H2SO4===BASO4 (precipitate) +2H2O

ba(oh)2 + 2hcl ==bacl2 + 2h2o

BaCl2 + H2SO4 ==BaSO4 (precipitate) +2HCl

AGnO3 + HCl ==AGCL(precipitate) +HNO3

2AGnO3 + BACl2===2AGcl(precipitate) +BA(NO3)2

AgNO3 + NaOH ==AGoH (precipitate) +Nano3 2agoH===AG2O (precipitate) +H2O

2AGNO3 + BA(OH)2 ==2agoh(precipitate) +BA(NO3)2

Basically, in junior high school and even high school, you don't need to consider the problem of ag2so4, so I won't list it. Satisfied.

SO2 is a weak reducing agent.

When dissolved in water, sulfite H2SO3 is formed.

Then the sulfurous acid reacts with NaOH to neutralize the acid and base.

Sulfite H2SO3 ionization step, first ionization of bisulfite HSO3- and H+ If there is not enough base, then it is only enough to neutralize the H+ ionized in this step, only this part of the first ionization of H+ is neutralized into water, and the remaining salt with sodium is bisulfite HSO3-, so the resulting product is NaHSO3 and water, remove the water that was previously combined with SO2, and the reaction formula is.

so2+naoh=nahso3

When there is enough alkali to consume the H+ ionized in the first step, then the bisulfite Hso3- will be further ionized to generate hydrogen ions and sulfite, HSO3-=H+ + SO3(2-), and the excess base will neutralize the H+ ionized in the second step, so the salt with sodium becomes sulfite SO3 (2-), and Na2SO3 is generated, and the reaction formula is.

2naoh+so2=na2so3+h2o

If you memorize it, you can remember it like this

SO2 is dissolved in water to form H2SO3, SO2 + H2O = H2SO3 ·· 1）

h2so3 + 2naoh = na2so3 + 2h2o···2）

1) Substitution (2) i.e. replace H2SO3 with SO2 and H2O

so2 + h2o + 2naoh = 2na2so3 + 2h2o ··3）

Then (3) remove a molecule of water from both sides, and obtain.

2naoh + so2 = na2so3 + h2o···4）

but, to know what type of sulfur dioxide reaction with sodium hydroxide belongs to:

SO2+2NaOH = Na2SO3 + H2O (AB+CD=AD+CB), which meets the definition of metathesis reaction, so it belongs to metathesis reaction, but it is not a neutralization reaction, there is no acid, only acidic compounds (SO2).

Now to give you a summary of the metathesis reactions there are those:

Common metathesis in aqueous solution:

Metathesis of acidic and basic compounds (including amphoteric compounds).

For example: SO2+2NAOH=NA2SO3+H2O

Metathesis of strong and weak acids.

For example, CaCO3+2H+=Ca2++CO2 +H2O.

Metathesis of salts and alkalis.

For example, CuSO4 + NaOH = Cu(OH)2 + Na2SO4

Metathesis of salt and salt.

For example, agno3+kcl=kno3+agcl.

Metadecomposition of complexes is generated, such as AGCl+2KCN=K[AG(CN)2]+KCl, Fe3++SCN-=[Fe(SCN)]2+, etc.

Additional note: In fact, I have solved this problem for the landlord, but a friend proposed that I think it is necessary to explain:

Indeed, there is a great deal of controversy about what kind of reaction this reaction belongs to, and I start from a simple definition, and judge from the valency of metathesis before and after the metathesis reaction.

Essentially, this reaction should be:

SO2 + H2O = H2SO3 (chemical reaction).

H2SO3 + 2NaOH = Na2SO3 + H2O (metathesis reaction, also neutralization reaction).

Synthetically write a metathesis reaction that we usually think of as a metathesis reaction.

In addition, it should be noted that there are many uncertainties in chemistry, such as textbooks that say that acids and alkalis are chemical compounds! Then hydrochloric acid is acid! But is he a compound? Typical mixtures!! What do you think???

When SO2 is dissolved in water, it forms sulfite H2SO3.

Then the sulfurous acid reacts with NaOH to neutralize the acid and base.

Sulfite H2SO3 ionization step, first ionization of bisulfite HSO3- and H+ If there is not enough base, then it is only enough to neutralize the H+ ionized in this step, only this part of the first ionization of H+ is neutralized into water, and the remaining salt with sodium is bisulfite HSO3-, so the resulting product is NaHSO3 and water, remove the water that was previously combined with SO2, and the reaction formula is.

so2+naoh=nahso3

When there is enough alkali to consume the H+ ionized in the first step, then the bisulfite Hso3- will be further ionized to generate hydrogen ions and sulfite, HSO3-=H+ + SO3(2-), and the excess base will neutralize the H+ ionized in the second step, so the salt with sodium becomes sulfite SO3 (2-), and Na2SO3 is generated, and the reaction formula is.

2naoh+so2=na2so3+h2o

When SO2 is insufficient: SO2 + 2NaOH = Na2SO3 + H2O

When there is an excess of SO2: SO2 + NaOH = NaHSO3 + H2O

MGO+H2SO4--- reaction type: combined.

Mg(OH)2+Hno3--- reaction type: acid-base neutralization.

Mg+CuCl2--- reaction type: displacement of the quiet.

MgSO4+BAC2--- reaction type: metathesis start-up solution.

MgCl2+NaOH --- reaction type: metathesis.

1.Chemical reaction: CAO+H2SO4=

2.Decomposition reaction: kclo3=

3.Displacement branch reaction: Zn+CuCl2=

4.Metathesis reaction: aBaCl2 + H2SO4 = acid reacts with salt) BNaOH+CuCl2= base reacts with salt) CBACl2+Na2SO4= salt reacts with salt).

The chemical equation is pure combustion.

H2SO4 + BACL2 ==2HCl + BASO4 ion equation pants do.

Basis void SO42- +BA2+ =BASO4