Science and chemistry in the third year of junior high school, a few small problems accumulated over

1, because CaSO4 will prevent the reaction from proceeding. 2. No, you can't. Because sulfuric acid does not react with the gas you are talking about, and sulfuric acid is absorbent.

Sodium hydroxide is alkaline and absorbent, while sulfur dioxide is acidic and cannot be dried with sodium hydroxide, while neutral gases such as oxygen and hydrogen are available. 3. Because BA can react with sulfate to form a precipitate, it does not react with hydroxide to form a precipitate. The slightly soluble AGCL appears to be precipitated after the reaction.

4. Because calcium carbonate precipitation will be generated, the salt will be impure. 5,1: Yes, since it is an ion, it must be charged.

2. Acid ions are hydrogen ions, that is, they have a positive charge. Preferably, because after adding barium chloride, silver chloride may be formed, and dilute nitric acid will not be dissolved. b, if there are sulfate ions in the solution, it will be neutralized after adding a sufficient amount of dilute hydrochloric acid, and there is no phenomenon after adding barium chloride, if there are no sulfate ions in the solution, so there is still no phenomenon after adding barium chloride.

C, the reason is similar to A, so ABC can not be judged, and D should add barium nitrate, if there is no precipitation, it means that there is no sulfate ion, if the precipitation is generated, add dilute nitric acid to the precipitation, the precipitation dissolves then there is no sulfate, and there is no insoluble!

1.The slightly soluble calcium sulfate adheres to the surface of the limestone, preventing the sulfuric acid from continuing to react with the limestone (i.e., it does not bubble).

2.Sulfuric acid is absorbent, not reacts with gas, but only changes physically, sodium hydroxide also has water absorption, but it reacts with sulfur dioxide, so it should not be used as a desiccant for sulfur dioxide. Water vapor can be removed from oxygen, hydrogen, etc.

3.Because the addition of BaCl2 can directly see that one generates a precipitate and one does not generate a precipitate, if it is replaced by AGCL, AGCL is almost insoluble in water, and the solubility of AGCL is worse than that of AgSO4, so there is almost no sound phenomenon.

4.If you use HCl to remove, it doesn't matter if you add more, as long as the last heat is used, the HCl gas will run out, and no new impurities will be introduced. However, if CaCl2 is added, one is to generate precipitate and filter, and the other is that it cannot be removed by adding too much, and new impurities are introduced, so it is better to use HCl.

"Point" should be "electricity"! Acid ions are ions, and the particles are all charged, so correct.

2: Correct. It should all be anions, look at the definition in the book, the definition of salt.

6.Barium chloride has chloride ions, which may react with the silver ions in the original solution to form a white precipitate (silver chloride), and is also insoluble in dilute nitric acid. The purpose of the reaction is not to produce barium sulfate, isn't this silver chloride confusing and impossible to judge?

c Ibid., silver chloride may be generated.

d If it becomes a barium carbonate precipitate in a lifetime, isn't it impossible to detect it, and it cannot be proved that it contains sulfate ions.

Let's talk about b, first add dilute hydrochloric acid to see if there is precipitation or bubble formation, exclude the interference of carbonate ions and silver ions, and then add barium chloride, if there is a precipitation generation, it proves that the original solution contains sulfate ions.

Calcium sulfate adheres to the surface of calcium carbonate and prevents the reaction from proceeding. 2. It must be concentrated sulfuric acid, which has the function of absorbing water, but it is dry alkaline gas, such as ammonia. Sodium hydroxide is also absorbent, so it can be used as a desiccant, and it cannot dry some acidic gases, such as carbon dioxide, because of the reaction.

3 Because it is the simplest method, it can produce barium sulfate precipitate with sodium sulfate, and does not react with sodium hydroxide. Because it is slightly melting, the phenomenon may not be obvious. 4. Calcium chloride is also fine, but it is more filtered than hydrochloric acid, so if it is a multiple-choice question, you must choose hydrochloric acid.

5 this. What is a dotted cluster of atoms, which should be changed to a charged cluster. The second sentence should be correct, at least I haven't seen acid ions are cationic, acid ions are ionic compounds composed of metals, and metals are cations, so the corresponding ones are anions.

6.It's very simple, it's B. Because it is necessary to check whether there are sulfate ions.

The first thing we think of is to add barium ions, but barium ions and carbonate ions can also produce precipitation, so we have to find a way to remove carbonate ions. Sulfuric acid can't do it, because it's the sulfate ion that we want to test.

Hehe, you'll understand these things in the first year of high school. Good luck

The slightly soluble CaSO4 covers the surface, so that the reactants are not in contact with each other, preventing the reaction from proceeding; No, after a reaction occurs such as NH3 with.

The H2SO4 reaction reduces the amount of gas; Because it doesn't react;

NaOH cannot dry SO2 and can react with SO2;

Solubility ratio of AGCL.

AgSO4 is smaller, while matter tends to be stable and natural.

AGCL ratio.

AGSO4 is more stable and does not convert, please refer to "Principles of Chemical Reactions" (senior 2) for details;

CaCl2 is formed with Na2CO3.

CaCO3, for the new impurity, CaCl2 will also have some residue, while.

HCl and H2CO3 can be removed by heating.

False, cl- is an atom; That's right; Add dilute hydrochloric acid, remove sulfite and carbonate, silver ions, and then add.

BACL2, plus.

Dilute nitric acid will.

Sulfite oxidation to.

Sulfate, a mixed solution of barium chloride and dilute hydrochloric acid, may be generated.

AGCL white.

Color precipitation, adding barium nitrate solution may have.

Carbonate, choose C

The use of sulfuric acid to produce a micro-volume will affect the volatilization of the gas, and if it is related to the calculation, it will affect the calculation.

Sulfuric acid has strong water absorption, which is his characteristic. This means that you have not fully remembered the physical properties of sulfuric acid, and solid sodium hydroxide also has water absorption.

3 Even silver chloride and sodium hydroxide will form precipitates.

Silver hydroxide decomposes just when it comes into contact with water.

The product produced with hydrochloric acid is sodium chloride, and carbon dioxide is a gas that volatilizes. Although calcium chloride will remove sodium carbonate, it will be removed, but there is a new magazine calcium carbonate.

5, neither of these sentences is true, 1

Chlorate is outside the list, 2 sentences, ammonium is outside the list.

Choosing B and adding hydrochloric acid first can remove unknown ions that may react, such as carbonate ions.

1. Encapsulate CaCO3 to prevent further reactions.

2. If it can't react with the gas, drying is to remove the water, and the original gas is sucked away, so it is meaningless to make this gas.

3. You probably made a mistake, it should be agso4 slightly soluble. If you use silver nitrate, then react with sodium hydroxide, you go to the book, and the resulting silver hydroxide is going to decompose.

4. Okay! It's just that it has to be filtered, which is too troublesome.

5. I don't know much about this, it should all be right. Because the acid is the anion of the acid, the cation of the acid must be the hydrogen ion positively charged, of course correct.

6. B, this question must be wrong in the first place, and A cannot rule out the interference of AG+. It should be noted that barium chloride is bifacial, with chloride ions. The addition of dilute hydrochloric acid in b can exclude its interference, and the interference of CO3 2- can also be excluded.

SO2 or SO3 may be formed in the reaction

Some are not necessarily reactions, but they may also be adsorption (which I don't understand).

Since it is to distinguish between two substances, the more obvious the difference, the better, the more precipitation and the faster the result.

Because of the problem of substance residues, the last supplement of impurity removal is to evaporate to obtain crystals, and the residue of CaCl2 will affect the result of impurity removal, while HCl will be volatilized during the evaporation process

This question is not very clear, I personally think that it is one right and two wrong, 1, the acid ion is an ionic group, which can also be said to be a charged atomic cluster. 2, is also an ionic group, but not an ion (just a personal opinion, not clear).

The answer is C, the reason for this question is not very clear, it seems that the test of sulfate ion is a mixture of barium chloride and dilute hydrochloric acid. (Sorry, I haven't read for too long and forgot)

The microlysis adheres to the surface of CaCO3 and prevents the reaction from proceeding.

2.Cannot react with gases Concentrated H2SO4 dry gas is because it is absorbent and the gas it dries cannot react with it.

3.Because silver chloride is less soluble than silver sulfate, silver chloride does not react with sodium sulfate.

4.The use of calcium chloride will introduce new impurities and make the table salt impure.

To test sulfate, dilute hydrochloric acid should be added to eliminate interference such as silver ions, carbonate, etc., in the addition of barium chloride.

1 b is not wrong.

Ammonium chloride chemical formula NH4Cl, formula amount.

Ammonium cation (ammonium; Chemical formula: NH4+) is a positive ion derived from an ammonia molecule. Ammonia molecules combine with a hydrogen ion to form ammonium ions (ammonia donating lone pairs). Because its chemical properties are similar to metal ions, it is named "ammonium".

So, there's nothing wrong with B.

2 Note that it is a sodium carbonate solution, and Na2O reacts with water: Na2O H2O 2NaO

So the correct answer is: Na2CO3 + CAoO H2O=CaCO3 precipitate + 2NaOH

The reduced solid mass is the mass of oxygen-trapped acorn produced.

According to the law of constancy of mass, the mass that generates O2 = + 2 - = according to the equation, 2kclo3 = mno2 = 2kcl + 3o2m

Next to the cherry blossoms of the sowang to 149 m = 96

The solution is m = so the mass of the generated KCI is.

The metathesis reaction, generally speaking, is a reaction with constant valence, where the copper reaction is (Cu 2-)-2 valence before and after, and the CO2 reaction is +2 valence before and after the reaction.

In this example, it is actually the neutralization of acid and base, and there are many metathesis reactions, which are commonly used in junior high school: (conditions that do not occur in parentheses).

Basically, there are 3 categories:

HCl + NaOH == NaCl + H2O (acid-base neutralization reaction).

agno3 + nacl == nano3 + agcl produce precipitate).

CaCO3 + 2HCl == CaCl2 + H2O + CO2 produces gas).

It is important to note that there are times when metathesis cannot occur:

CaCl2 + H2O + CO2 == CaCO3 2HCl (Error).

Weak acid cannot replace strong acid, although precipitation is produced, but it cannot react!

CO2 + Cu(OH)2 = CuCO3 + H2O is a metathesis reaction.

The four basic types of reactions are classified as follows:

Chemical reaction ab

Decomposition reaction AB a b

Displacement reaction A BC AC B

Metathesis reaction: AB CD AD CB

Remember the above formula and just put the reaction formula in.

In other words, this should be the reaction of calcium hydroxide with carbon dioxide.

This is the reaction of the base with an acidic oxide, which is the same principle as the absorption of carbon dioxide by sodium hydroxide. The product must be the acid oxide corresponding to the acid oxide and water. The same is true for alkaline oxides that react with acids.

sio2+2naoh=na2sio3+h2o

It should be a metathesis reaction rather than a neutralization reaction.

If two liquids are miscible with each other, they are solvents and solutes to each other, that is, it is okay to designate either as a solvent, and the other is a solute. It is customary to use a large amount as a solvent and a small amount as a solute.

However, if one of the liquids is water, it is customary to specify it as a solvent regardless of the amount of water.

52 degree liquor is a volume concentration.

As long as there is water, no matter how much or how little it is, water is a solvent...

Generally, if there is water in the solution, water is considered as a solvent.

General provisions, conventions. End.

When there is water, it must be a solvent.

That's what my friends say.

Endothermic reactions: most of the decomposition reactions, C, Co, H2 reduction of metal oxides, barium hydroxide with eight crystal water and ammonium chloride reaction, most of the salt hydrolysis reactions, a few chemical reactions (generally not required to master).

Exothermic reactions: most of the chemical reactions, acid-base neutralization reactions, metal and acid reactions, metal and water reactions, combustion reactions, ** reactions.

Exothermic concentrated sulfuric acid, sodium hydroxide solid NaOH...

Endothermic ammonium nitrate NH4NO3

Glucose C6H12O6... In junior high school, remember that ammonium nitrate absorbs heat when it encounters water, such as active metal, strong alkali, and concentrated sulfuric acid to extothermic.

Many of the things people use now are organic synthetic materials, such as many glasses are made of plexiglass, of course, the windows and tires on the car, the plastic bags used in life, the chassis on the induction cooker, etc. It can be said that organic synthetic materials have been able to replace the high-temperature functional role of some metals in many aspects! Plastics, rubber, and man-made fibers are all organic synthetic materials.