A summary of the definition of chemistry from the third year of junior high school to the second yea

The third chemical formula: 1. The reaction between the substance and oxygen: (1) The reaction between the elemental substance and the oxygen:

1.Magnesium burns in air and prepares for 2mg: 2mg + O2 to ignite 2mgo 2

Iron burns in oxygen: 3Fe + 2O2 ignites Fe3O4 3Copper is heated in the air or carried:

2cu + O2 heat 2cuo 4Aluminum burns in the air to imitate which burns: 4al....

HF is indeed a weak acid, CSOH is indeed a strong base, and of course NAOH is also a strong base.

The reason why HF is a weak acid is because F is a second-period A group element with a small atomic radius, the outermost shell of 7 electrons, and the electron-withdrawing ability is the strongest of all elements. When combined with H to form HF, HF is a weak acid because the chemical bond in the middle of HF is very strong and not easy to dissociate. The chemical bonds of halogen elements in the hydride from top to bottom are weakened and easily dissociated, and they are strong acids from HCl, and they are becoming more and more acidic.

CSOH is a strong base. CS is an alkali metal element, and its most ** oxide corresponding hydrate CSOH is a strong base. That is to say, the hydroxides of alkali metal elements are strong bases except for Lioh, and their alkalinity is enhanced from top to bottom.

I am a high school chemistry teacher, and I explain it as follows:

HF can react with SiO2, which is a special property of HF, not because HF is a strong acid. Strong acids such as HCl do not react with SiO2. Haoh is a strong base that can react with HF, which is right, neutralizing the reaction.

CSOH is indeed a strong base, and NaOH is also a strong base. This is not a contradiction.

Hf is a weak acid because it is not easy to ionize H and is not a matter of electrons gain or loss. A weak acid is an acid that is partially ionized.

The outermost shell of the f atom has 7 electrons, and it is easy to obtain electrons.

HF is a weak acid, absolutely. If you have an analytical chemistry book, you can know that it has KA and the general KA is a weak acid (except for sulfuric acid, because its KA is still very large). There is also a reaction between HF and silica, because silicon has fluoride absorption, not relying on acidity, that is, it can react with F, if you change to hydrochloric acid, you will find that silica and hydrochloric acid do not react.

To judge the strength of a base, it is necessary to look at the metallicity of the metal element that forms the alkali, the stronger the metallicity, the stronger the alkalinity of the most ** hydroxide formed, because the metallicity of CS is stronger than Na, so the corresponding alkalinity is stronger. You can take a look at the high school chemistry course on the structure of atoms, which is explained.

Obviously, one of the teachers said it wrong, maybe you heard it wrong.

In high school, you only need to know that HF is a strong acid (acidic so strong that even glass SiO2 can corrode), but because the non-metallic nature of F in HF is extremely strong, and the electronegativity of F is extremely great, so that HF is difficult to ionize in aqueous solution, and the concentration of hydrogen ions in HF solution of grade 1 mol L is very only mol L (I exaggerated it) From this point of view, HF is very weak (weak is his ionization ability).

If you're a liberal arts major, just remember it; If it's science, your teachers will talk about it.

I reckon you're liberal arts.

1) HF is a weak acid, because it is very stable, not easy to decompose, and difficult to react with alkali, so it is a weak acid.

2) "7-electron particle easy to one electron" refers to f2, not hf

The F in HF already shares electrons with hydrogen, which means that fluorine has gained one electron, not 7 electrons, but 8.

There is a contrast between the strength of acid and alkali, and it can only be relative to the strong and weak! Due to the strong electronegativity of the F element, it is not easy to dissociate! But it's easy to get electrons!

The answer is d

Pure substance: A substance composed of a single substance is called a pure substance, and pure matter includes both elemental substances and compounds.

A substance containing only one element may be elemental, i.e., it may be pure, but the substance may be a mixture of allotropes. For example, red phosphorus and white phosphorus, graphite and diamond mixtures, so it could be a mixture as well.

d Contains an element that may be graphite in the case of carbon, or it may be activated carbon or something like that.

Pick D for example.

O2 (oxygen) and O3 (ozone) are allotropic forms.

High One Chemistry P18-P19

Solution: d can be used as an example: the substance mixed with oxygen and ozone has only element O in it, but it is a mixture.

So a mistake.

For example, Fe is composed of Fe elements, which is both elemental and pure, so BC is wrong.

da, the same element is not necessarily pure, such as ozone and oxygen b, there must be two elements in the compound.

C, the same as A, so choose D

First of all, according to the change of concentration, it is judged that the coefficient of AB is equal, the concentration of ABC decreases when X=130min, the old lease of the nucleus indicates that the volume increases, the pressure decreases, and the coefficient sum of the two sides is equal, so the balance does not move, which is in line with the figure on the right.

A false. At 40 min, the rate increases and decreases, while v is inverse and v is positive, and the equilibrium moves in the direction of reverse reaction. So only an increase in temperature can be satisfied.

Heating up, equilibrium reverse shift, indicating that the reverse direction is endothermy, and the positive direction is exothermic.

C false. The average reaction rate of a before 8 min = (

B false. k1=2*2/1*1=4 k2=

d correct.

Select D for this question. The analysis is as follows:

a. As can be seen from the figure, the concentrations of cavity groups a, b, and c have become three-quarters of the original at 30min, and the balance does not move, so the disadvantage is to reduce the pressure; If it is cooling, the positive reaction rate and the reverse reaction rate are reduced, but it is impossible to reduce them by the same multiple.

b. It should be.

c. According to the ratio of the stoichiometric number is equal to the ratio of the change in the quantity concentration of the substance, so x=l in the reaction equation, but if the positive reaction is an endothermic reaction, the temperature will be increased at 40min, and the equilibrium should move to the direction of the positive reaction.

d. Since the chemical equilibrium constant is only related to temperature, k = the square of the concentration of product c divided by the product of the concentration of a and the concentration of b, so that the square equal to 2 divided by the product of 1 and 1 is correct.

Actually, none of them are wrong.

This is a metathesis reaction in which the tendency of the metathesis reaction is to proceed in the direction of decreasing ion concentration (in solution). Because copper sulfate, barium chloride and copper chloride can be ionized into corresponding anions and cations in aqueous solution, only barium sulfate is not ionized and dissolved in aqueous solution, which is a precipitation.

Gaoyi Chemical: It is said that copper chloride is ionized in the solution, and there will be no copper chloride precipitation. If the ion equation is written, it is BA2+ +SO4 2- = BASO4 (precipitation), where chloride and copper ions do not participate in the reaction.

Junior Chemistry: It is true that copper chloride is generated, but it is ionized into chloride ions and copper ions in solution. If the chemical equation is written, then CuSO4 + BACL2 = BASO4 (precipitation) + CuCl2, where the reaction takes place.

They all make sense, they are all correct, you can justify yourself! It's complicated, and I hope you'll turn the corner!

Cu2+ Cl- are both ions that do not react.

Copper chloride is present in solution form.

Won't react.

Copper chloride is a salt, which can be completely ionized by hydrolysis or melting, and is a strong electrolyte, which exists in ionic form before and after the reaction.

From this reaction, the products are barium sulfate and copper chloride, but the ion reaction is generally carried out in solution, that is to say, at the beginning, the ions in 4 are in it, and the barium ion and the sulfate ion are combined, and the copper ion and chloride ion are still in the solution, it should be said that there is no change in the existence of these two ions before and after the reaction, but if you evaporate the solution, you will get two products, barium sulfate and copper chloride. In the third year of junior high school, it was not written that they did not react, because the corresponding concept had not been introduced at that time, and after learning ionic reactions in the first year of high school, it was natural to understand the principle and truth of it

The presence of chloride ions and copper ions in the copper chloride solution is not copper chloride, so after the completion of this reaction, the presence of chloride ions and copper ions in the solution is correct.

The essence of the reaction is the reaction of sulfate and barium ions, and the barium ions and sulfate generate a water-insoluble barium sulfate precipitate, so that there are copper ions and chloride ions left in the solution, which becomes copper chloride.

This reaction produces a new substance, copper chloride, but copper chloride is composed of chloride ions and copper ions, which are both ions before and after the reaction in solution. The two ions do not react.

The remaining Cu ions do not react with Cl ions.

It's just a combination of anion ions.

For example, CuCl2 ionizes Cu2+ and Cl- ions in water and does not react.