High school chemistry questions, high school chemistry questions

Gas washing cylinders generally have the following functions:

1. Washing gas 2. Collecting gas (divided into up, down, and draining method) 3. Observing the gas flow rate (see bubble velocity).

Long in and short out: gas washing, upward air exhaust method, observation of gas flow rate; Washing gas and observing the gas flow rate require the gas to be in full contact with the liquid in the bottle, so it should be long in and short out; The upward exhaust method requires air to go out from above, so it also needs to be long in and short out.

The safety bottle of anti-sucking only plays the role of holding the liquid when the sucking occurs to prevent the liquid from entering the reaction vessel, so the requirements for this are not high, but it is best to have both short or short inlet and long out (to avoid the incoming liquid does not pass through the catheter orifice and sucks again).

The principle of sucking is caused by the difference between the gas pressure inside and outside the device (when the external air pressure is the internal air pressure, the air pressure presses the liquid into the device, which is suction) If the end of the catheter is just flush with the liquid level, see if the liquid has not passed the catheter orifice, if it has not passed the catheter orifice, the air pressure difference can be generated.

Take, for example, children's shoes.

In the process of gas drying (or impurity removal), if a solution is used, then it needs to be long in and short out; If it is short in and long out, it will press the liquid over or gasp. The role of the safety bottle can indeed play a certain degree of sucking, but it cannot fundamentally solve the problem, so don't be mistaken about whether it is a long in and short out, or a short in and long out.

There is no principle for suction, only the reason, which is caused by the unequal pressure on the two sides. There are no specific examples and no explanations. If the end of the catheter is just flush with the liquid level, there is a possibility of sucking or not, and this specific problem is analyzed on a case-by-case basis.

The o) on the sides of the middle two squares: 8 1 2 4

o on each edge of the box: 12 1 4 3

The number of o's I calculated is 4+3 7

Problem 2: If sulfite ions are present in the solution, s(+4) will be oxidized to s(+6), interfering with the experiment.

Question 3: If you are a junior high school student, you don't need to think about this problem. If you are a high school student, please change the test of CO32- ions to "Unknown liquid is added to a sufficient amount of BaCl2 solution to produce a white precipitate, and then dilute hydrochloric acid is added to produce a gas that can make the clarified lime water turbid."

The corresponding test of HCO3- ions is "adding a sufficient amount of BaCl2 solution to the unknown liquid does not produce white precipitate, and then adding dilute hydrochloric acid produces a gas that can make the clarified lime water turbid." ”

Question 4: Glass wool belongs to a category in glass fiber, which is a man-made inorganic fiber. Glass wool is a molten glass fiber, forming a cotton-like material, the chemical composition belongs to the glass class, is an inorganic fiber

It has good molding, small bulk density, thermal conductivity, thermal insulation, good sound absorption, corrosion resistance, and stable chemical properties.

Obviously, this is a problem for junior high school students, but it can be understood in this way: 1. It is not necessarily alkaline that is alkaline in the solution, and some salts make the solution acidic and alkaline due to "hydrolysis". (Note:.)

2. Nitric acid is not studied in the junior high school stage, and it is not required to learn the non-hydrogenated reaction between metals and nitric acid. (In the first year of high school compulsory 1 Chapter 4 non-metals and their compounds, we will learn about oxidizing acid nitric acid in depth) 3. The test of bicarbonate is a qualitative requirement in junior high school, mainly compared with the properties of carbonate. (In the first year of high school compulsory 1 Chapter 4 of non-metals and their compounds) 4

Glass wool is composed of glass fiber, and there are many classifications according to different functions: such as heat insulation, anti-riot, etc., which are inorganic materials.

1.Carbonate, bicarbonate will be hydrolyzed to produce hydroxide ions.

The first one is due to the hydrolysis of anions! 2 is that if sulfite ions are present in the solution, s(+4) will be oxidized to s(+6), which will interfere with the experiment.

Question 1 in the recommended answer, which should be corrected, the strong alkali and weak acid are alkaline.

O3 Yes, it has strong oxidation and can drift. Naclo and Ca(clo)2 do not, they can drift, but it is the HClo that they react to produce that is bleaching, not that they have it.

1.NH3 is more polar than PH3, so its lone pair is more exposed and more receptive to hydrogen ions, so its aqueous solution is more alkaline.

2.There are two kinds of isoelectron concepts, one is as you said, and the other is that the number of atoms is the same, and the number of electrons is the same.

3.The hardness of a metal is mainly related to its nature. Another major reason is how tightly the metal atoms are arranged in the metal crystal. The hardness of calcium is large because the radius of calcium ions is small and the ionic charge is large, so the atoms in the crystal are tightly bonded.

4.It can be compared, just use two substances to mark each other, and the harder substance can have a noticeable scratch on the softer substance.

5.The melting and boiling points of potassium and calcium are more difficult to say, and it is recommended to check the data, because the hardness and melting and boiling point of metal crystals generally do not have a very universal law.

6.Oxidity or reduction depends on the valence state of the element compared to its limiting valence state. For example, the highest and lowest prices of O in H2O2 are 0 and -2, respectively. Therefore, oxygen in hydrogen peroxide should be both oxidizing and reducing.

8.The most reactive elemental should be sodium.

9.Acidic: HCO4 H2SO4 H2CO3

10.The relative atomic mass of an element is unique, but the mass number is not. Because the mass number is the sum of the number of neutrons and protons in the nucleus, the mass number of the isotope atoms is different.

11.Judging the crystal type of this substance requires a certain amount of knowledge. Then it's easier to extrapolate by analogy.

Silicon nitride is similar to diamond in structure, in the cage structure, the nitrogen atom occupies the vertex of the four hypomethyl groups, and the silicon atom occupies the rest of the vertices, it is obvious that the nitrogen atom still has lone pairs, and the silicon atom can obviously connect other atoms, so it can be inferred that the silicon nitride should be a spatial network structure, which is naturally an atomic crystal. Of course, there must be more obvious hints during the exam, so you don't have to think about it very complicated. Sii4 can be compared to carbon iodide, or more directly, linked to methane, carbon tetrachloride, silicon tetrachloride, etc., which are obviously molecular crystals.

I sent it with a mobile phone at school.,So it's not very clear.,If you don't understand, you can ask.,Or hi me).

1.Ammonia is more soluble in water.

2.The concept of isoelectrons is that the number of atoms is the same? It should be the same number of electrons, such as co, n2, so there is no problem like the outermost electron.

3.It can be explained by metal bonds, or it can be said by the number of electrons, in metals, the number of charges carried by cations is large, the Coulomb force is large, and the molecules are strongly absorbed. （f=kq1q2/r2）

Same as 36.After looking at the reaction, the valency of the element increases, which is reducible, decreased, and oxidized.

7.To put it simply, it is highly metallic and more volatile electrons. 8.

1. Why is the aqueous solution of NH3 more alkaline than PH3?

Because ammonia and water should react to form ammonia monohydrate, weak alkali; And hydrogen bonds should also be formed between ammonia and water2, and the concept of isotons is that the number of atoms is the same, and the number of electrons in the outermost shell is the same?

Yes4, Can the hardness of quartz and silicon carbide be compared?

OK. It is related to the length of the bond, and the former is stronger than the latter.

It will be better to look for it yourself on the textbook.

1. Double hydrolysis is a hydrolysis reaction in which the acid ions of weak acid and cations of weak alkali promote each other, cations generally consider 3-valent iron ions and aluminum ions, and anions generally consider bicarbonate, carbonate, metaaluminate, etc.

Example: The principle of a foam fire extinguisher.

al2(so4)3+6nahco3==3na2so4+2al(oh)3↓+6co2↑

2. That's right (not sure).

3. S02, NO, NO2, H2S, etc.

The hydrolysis reaction is not equal to double hydrolysis.

Hydrolysis in general is weak.

In addition to double hydrolysis.

Generally, the hydrolysis equation is written with a double construction number, and the gas in the product is not written with the " symbol, and the precipitation is not written with the " symbol, but the reaction equation of double hydrolysis is written.

The mechanism is not clear, and it can be regarded as either electrophilic substitution or nucleophilic substitution.

If it is regarded as an electrophilic substitution, it is under the action of acid, the O of acetone obtains an H+, which makes the CO double bond open to form a carbocation (CH3)2C(OH)+. Carbocation is added at the paraposition of phenol to form a molecule of (CH3)2C(OH)-C6H4OH. Then hydroxyl O gives another H+, which is detached into water to form a new carbocation (CH3)2C(C6H4OH)+, which is added in the paraposition of another phenol, and finally (CH3)2C(C6H4OH)2.

If it is regarded as nucleophilic substitution, it is that after the phenolic hydroxyl group ionizes out of H+, the negative charge on O is transferred to the benzene ring paraposition, and the carbonyl group of acetone is nucleophilic addition to form (CH3)2C(OH)-C6H4OH. Later, another phenol also forms a para-negative charge, which performs nucleophilic substitution on the product just now, displacing the hydroxyl group to form (CH3)2C(C6H4OH)2

It is also possible to substitute the alcohol hydroxyl group for a second phenol para-hydrogen atom.

A one-time addition is impossible, and the unsaturation is not satisfied.

1: "Displacing an element" is not exactly the same as "displacing reaction". The displacement reaction is usually referred to:

The reaction between the elemental element and the compound that occurs in the solution displaces a certain element, including the displacement reaction, but the area is more extensive.

2: The substance is melted, and the co-nucleus guesses whether the valence bond is broken, depending on what kind of substance. For example, when sodium hydroxide is melted, the covalent bond between hydrogen and oxygen is not broken, and when the elemental silicon is melted, part of the covalent bond is broken.

3. Under normal conditions, N2 and O2 cannot be directly combined into No2, N2 and O2 will become at high temperature or electric shock.

no, no continues to oxidize and becomes no2.

N2 and O2 will turn into No at high temperatures or electric shocks, and react with water to become NO2