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These two categories basically fall under the category of metathesis reactions.

Metathesis reaction conditions, gases are produced, precipitation is produced, and refractory ionization (e.g., water) is produced, and salt requires both salts to be soluble in water.

In the reaction of salt and acid, a salt is added to be soluble in acid.

The above statement meets the requirements of the high school entrance examination.

To judge whether two substances can react, first assume what can be produced by reaction, and then see whether the product meets the conditions for metathesis reaction.

For example, sodium chloride and dilute sulfuric acid are assumed to react to produce sodium sulfate and hydrochloric acid. No gas, no precipitation, no difficult ionizations, no reaction.

1.The reaction of salt and salt satisfies the conditions: one is soluble in water, and the other is precipitated, gas or water.

2。The reaction of salts and acids satisfies the conditions: there is a precipitate, gas or water in the product.

Sodium chloride and dilute sulfuric acid do not react because no precipitate, gas or water is formed.

Among the products are refractory substances, refractory ionization substances, and volatile substances, and the reaction can be carried out.

Sodium chloride and dilute sulfuric acid are not sodium chloride with silver nitrate dilute sulfuric acid with barium chloride.

The principles followed are: low free energy and good product stability.

The condition to be met is that the stability of the salts produced is better than those participating in the reaction.

The reaction of salt and salt must produce water. Carbon dioxide. Precipitation. Only one of the three can react.

The reaction between salt and acid must conform to the principle of strong acid to weak acid, for example, hydrochloric acid and sodium carbonate produce sodium chloride. water and carbon dioxide;

Sodium chloride and dilute sulfuric acid cannot react! Reason: It does not conform to the principle of metathesis reaction!

Generally speaking, at least one substance needs to be soluble in water in order to react.

The general judgment of the understanding is.

At the middle and high school levels, it is understood that it is in line with the metathesis reaction.

That is, there is precipitation, gas, water generation.

A little deeper is that the two react to form more stable products (complexes, complexes, difficult ionizations) and then go deeper until the third year of high school or even college, which involves some chemical energy changes, which is more troublesome, and you can take a look if you are interested.

Salts and acids are strong acids to weak acids in junior high school, such as hydrochloric acid to carbonic acid.

In high school, there are also difficult volatile acids to produce volatile acids, such as concentrated sulfuric acid to produce HCl

There are high to low in order: hydrochloride acyl chlorophenol hydroxyl amino group.

Let y=2 x

Then the original equation can be written as.

y^2+ay+(a+1)+0

where y>0

First guarantee =a 2-4a-4 0

a>2+2 2 or a<2-2 2

y=[-a±√(a^2-4a-4)]/2

Because taking a positive sign is greater than taking a negative sign.

Therefore, as long as you ensure that when you take the correct number, you can ensure that there is a solid root.

a+√(a^2-4a-4)]/2>0

a^2-4a-4)>a

When a<2-2 2, the inequality holds.

When a>2+2 2, (a 2-4a-4) > a>0

a^2-4a-4>a^2

4a-4>0

a<-1

Obviously, there is no solution to the inequality at this point.

So a<2-2 2

It is generally called liquefied petroleum gas.

Main ingredients: ethylene, ethane, propane, propylene, butane, butene, etc.

Appearance and properties: colorless gas or yellow-brown oily liquid, with special odor.

If there is an olefin, it reacts with the carbon tetrachloride solution of bromine and fades.

First, clarify the meaning of the abscissa and ordinate representation, and then analyze and answer the specific questions.

With a sodium chloride solution, the beginning of the period is the electrons of water, so it is obvious that the electricity is wasted.

With a copper salt solution, the electrons are obtained directly from the copper ions.

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Order: barium hydroxide, sodium hydroxide, potassium metaaluminate.

Easy to understand with ionic equations:

2oh-+co2+ba2+=baco3↓+h2o

co32-+h2o+co2=2hco3-

baco3+h2o+co2=ba2++2hco3-

alo2-+2h2o+co2=al(oh)3↓+hco3-

The total charge of the cation = the total charge of the anion.

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Hope, thank you.

Copper ions have strong oxidation, and hydrogen peroxide has strong reducing properties, so redox occurs to produce Cu, oxygen and sulfuric acid.

Regardless of whether it reacts with an acid or with a base, the amount of hydrogen produced by aluminum is equal.

Therefore, as long as the amount of hydrogen produced by the reaction of iron and hydrochloric acid is equal to the amount of hydrogen produced by the reaction of silicon and sodium hydroxide. fe-h2

si--2h2

So the mass ratio of iron to silicon is 56:14=4:1

The amount of aluminum is arbitrary.

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Steps: Take a small amount of the two substances in the same test tube, add water to dissolve, shake, and produce a white precipitate (aluminum hydroxide), and ammonium sulfate (colorless solution).

Conclusion: Aluminum sulfate and ammonia water react to form aluminum hydroxide and ammonium sulfate.

There is only one step reaction between aluminum sulfate and ammonia, which is Al2(SO4)3+6NH3·H2O=2AL(OH)3+3(NH4)2SO4

Chemical Equation:

al2(so4)3 + == 2al(oh)3↓ +3(nh4)2so4

Ionic Equation:

2Al3+ +== 2Al(Oh)3 +6NH4+ Because ammonia is a weak base, Al(Oh)3 cannot be turned into AlO2- ions, and only a strong base can react with aluminum hydroxide.

and N2, indicating that their average relative Hopper Leak molecular Heldane mass is 28.

Since the relative molecular mass of CO is 28, its amount can be arbitrary.

The key is H2 and CO2. Using the cross method, the volume ratio of CO2 and H2:

So as long as the volume ratio of CO2 to H2 is 13:8, it is right. Or.

My opinion, after all, I learned it a long time ago:

When the atoms in a molecule are separated, the energy is absorbed by the bond-breaking reaction, and the recombination of the atoms is the bond-forming reaction, which releases heat.

Therefore, if the energy required for bond breaking is large, it means that the binding force between the atoms is strong, and the matter is more stable.

As for the kind of atoms that are easier to combine with each other, relatively speaking, those that are far apart in the periodic table, have large differences in atomic properties, and have large differences in electronegativity, etc., are easier to combine.

The next question, the principle of chemical reactions: the process by which molecules break into atoms, and the atoms rearrange and combine to form new substances. The type and number of atoms do not change, the type of atom is determined by the number of protons in the nucleus, to change the type of atom, to change the number of protons in the nucleus, that is, nuclear fusion, nuclear fission, which is physically defined as not a chemical reaction.

The energy required for this reaction is a geometric multiple of the chemical reaction, and the chemical reaction cannot meet the energy conditions in thermodynamics.

The first statement is correct. Atoms are the smallest particles in chemical change. A chemical reaction is the recombination of atoms, during which the nucleus remains unchanged.

The atoms are recombined into new molecules, and the type and number of atoms remain the same, so there is a law of conservation of mass. The type of molecule must change before and after the reaction, and the number of molecules may change.

The students who can ask this kind of question are generally students who have just gone deep into chemical reactions in high school, and they have not been exposed to many reactions, and they lack empirical support for many theoretical descriptions.

1.The two basic properties of gases are diffusivity and compressibility.

2.Because the distance between the gas molecules is large and compressible is wide.

3.In the case of the gas itself, it is caused by its own characteristic diffusivity, whereas in the second law of thermodynamics, the sum of the entropy of the system and the entropy of the environment increases when all macroscopic processes proceed spontaneously. Gas diffusion is a macroscopic spontaneous process, then the entropy value of the gas must increase, and the larger the volume, the greater the entropy value, as far as the gas is concerned, there is no maximum entropy value, that is, the larger the volume, the more obvious the spontaneity of the macroscopic process, so the volume can increase indefinitely, that is, it can expand indefinitely.

4.The pressure of the gas is caused by the constant collision between the gas molecules and the walls of the container due to the irregular movement of the gas molecules in space. The collision must be forceful, so this force is defined as the pressure of the gas.

The root cause is the irregular movement of the gas. In addition, the pressure of the gas is related to two aspects, one is the speed of the gas molecules, and the other is the number of molecules per unit volume.