2 chemistry questions in the first year of high school need more authoritative answers .

Problem 1: Sodium has a shape before it is put in, not a spherical shape, and it looks a little yellowish, and after being put into water, it becomes a shiny ball, indicating that the sodium oxide on the surface reacts with water, and the sodium at the back becomes a small ball because the sodium reacts with water and releases a large amount of heat to melt the sodium with a lower melting point, and the sodium is not miscible with water, so it can only float on the water surface.

Problem 2: In fact, there is no reaction with oxygen, because a layer of oxide film blocks the reaction between aluminum and oxygen, so aluminum only melts instead of reacting, and alumina cannot react with substances in the air, so aluminum does not react.

To react is to react with the fuel and the air.

1.Observed through the eyes.

Sodium is first melted when heated in the air, and when burned, it reacts violently to produce a yellow flame and produce a light yellow substance.

O2 == 2Na2O2 reacted. Combustion itself is a chemical reaction.

1: The NA block has become spherical.

2: The combustion process is the process of oxidation.

Problem 1 - Melt and a piece of sodium metal can be seen turning into a small silvery-white ball.

The whole phenomenon can be described in five words: floating melt swimming red. Floating, as sodium is less dense than water, it floats on the surface of the water. Swimming, sodium reacts with water to form hydrogen, which makes the sodium unbalanced and therefore swims.

Melt, already mentioned. Ring, the sound of hydrogen gas emitted during the reaction (ci ci). Red, after the reaction, add a few drops of phenolphthalein (an alkaline indicator), due to the formation of 2Na + 2H2O = 2NaOH + H2, there is a red phenomenon.

1. Turning into a small silver ball can be explained.

2. It does not drip down because there is an oxide layer of wrapping, and this layer of wrapping will be destroyed when burning, since it is combustion, of course, a chemical reaction occurs.

It doesn't matter what shape you burn it in, it melts and turns into a small round silver ball.

In fact, because Na is very lively, as long as you put it on the asbestos net, it will melt itself and eventually it will burn (yellow light).

Do you mean thermite reaction or what?

It was through the discovery that sodium was fused into a shiny ball.

And the sodium is melted.

After sanding the aluminum surface with sandpaper.

Heat in air.

The outer layer of aluminum is combined with oxygen (a chemical reaction occurs).

A dense oxide film is quickly formed, so that the aluminum inside does not react with oxygen.

Aluminium has a melting point of 660 and melts when heated continuously, but there is no reaction.

1。Ba(HCO3)2 is not a precipitate, so it does not react.

2。In fact, it is the ionic equation, sodium bicarbonate can react with barium hydroxide is to react HCO3+ with OH- to produce H2O and CO2Sodium bisulfate can react with barium chloride and barium hydroxide, because sodium bisulfate is completely ionized into Na+, H+, (SO4)2-, so sodium bisulfate can react with barium chloride and barium hydroxide.

Speaking of sodium carbonate, it ionizes as Na+, (CO3)2-, and can react with both barium chloride and barium hydroxide.

1. Yes. After evaporation, NH3·H2O is decomposed into NH3 and H2O and leaves the system, while NH4Cl is decomposed: NH4Cl = (δ)NH3 + HCl, which is transformed into two gases leaving the system. The remaining solid is KCL.

2. In fact, the main component in ammonia is still NH3, and only a small amount of NH3 reacts with H2O to form NH3·H2O. Note here that "ammonia" refers to "aqueous solution of ammonia" and not "aqueous solution of ammonia monohydrate". Of course, the evaporation solution is gone, and there is no ......NH3 and H2O all turn into gas and disappear.

3. It seems that it will be filtered before drying the seawater......So of course there can be no sediment.

1 Ammonium chloride, ammonia monohydrate is unstable and decomposes by heat Potassium chloride is relatively stable 2 The main components in ammonia water are NH3, NH4+, H2O, OH- ammonia flies Ammonia monohydrate is unstable and decomposes into water and ammonia As a result, Shenma is a floating cloud.

3 The question of this question is not good, it should be the crude salt purification of seawater, BCD is soluble impurities, and A is filtered out during the purification process, so choose A

Do you understand, pure hand beating, exhausting to death

1.Yes, the decomposition of monohydrate and ammonia is volatilized by ammonia during evaporation, and NH4Cl is decomposed into NH3 and HCl by burning after evaporation, so pure KCl 2 can be obtainedThere are many ingredients, such as ammonia monohydrate, ammonia dihydrate, ammonia trihydrate, etc., but only when the ammonia composition is ammonia monohydrate, ammonia is volatile, if the solvent is evaporated and there is nothing correct, when the seawater is salted, the density of sediment is large, and it is precipitated below, but the other components and NaCl are almost dissolved in the solution, and they are ejected together with the decrease of the concentration of the solvent.

1. It can be purified. Ammonia monohydrate is decomposed by heat to produce ammonia and water, ammonia runs away and the water is evaporated; Ammonium chloride is also easy to decompose when heated, producing ammonia, and the remaining chloride ions do not affect the experimental results, and the final result is potassium chloride.

2. Probably not. Ammonia is a product of ammonia dissolved in water. If the solvent is evaporated, the ammonia is split into ammonia and water, and finally only water remains.

3. Because sediment is a substance with a diameter greater than 100nm, which can be removed in the first step of filtration, while B, C, and D cannot be filtered, A is an impurity that cannot exist.

1 Yes, reason: ammonium chloride will decompose when heated (ammonium chloride is a volatile acid weak alkali salt, even if the textbook does not tell you that ammonium chloride will decompose when heated, we can push it out--- the salt of hydrochloric acid and ammonium hydroxide must be decomposed by heat, after all, it is a weak alkali salt).

2 Yes, because ammonia is a weak base, ionized hydroxide only accounts for a few, and when it is evaporated, there is nothing, because ammonia itself is obtained by ammonia dissolving in water, which is the reverse of the process.

3 This question is typical of nerds, because we know that even if it is purified, it is impossible to be free of impurities. Even trace amounts are called impurities! We will discuss the topic, and if we have done this question, we will forget about it, and we will not take the college entrance examination.

BCD doesn't decompose when heated, so we take it for granted that the seawater has been filtered and the sediment has been filtered out. Solve the problem, don't look at it again!

1.If there is ammonium chloride, ammonia monohydrate, and potassium chloride in the solution, can KCL be purified by evaporating the solvent and burning the solids? What is the principle?

Yes. nh4cl＝∆＝hcl↑＋nh3↑

nh3·h2o＝∆＝nh3↑＋h2o↑

In the end, only KCL remained

2.Is the main ingredient in ammonia ammonia monohydrate? What happens if the solvent is evaporated?

Be. Nothing left after steaming.

3.The impurities that cannot exist in the process of drying salt in seawater are a sediment b calcium chloride c barium chloride d sodium iodide answer choose a, solve why? Or is the answer wrong.

Looks like purification? Salt drying is carried out in salt pans to obtain coarse salt. And what men used to eat, there was mud and sand.

1.Redox reactions.

2.Chlorine and lime water.

3.Watch it a few times and remember it.

is a normal salt, and NaHCO3 is an acid test salt.

5.Electrolyte: Acid-base salts belong to electrolytes, which are not necessarily conductive, and electrolytes are conditionally conductive.

6: The most important thing is to read books! Summarize and summarize by yourself, be more impressed, and the efficiency will improve quickly!

1. Whether the valency of the ions changes before and after the reaction 2

1. There is no need to "see", and the laws are summarized on the basis of facts, which are empirical laws, so your job is to accept and reflect the facts.

2. Meaningless questions.

3. Just remember, it is born pale yellow, what if you don't remember? There are many such cases, remember, without a certain factual basis, it is impossible to learn chemistry well.

4. Polyacids, such as carbonic acid, sulfuric acid, etc., when they become salts, there will be acid salts, simply put, the ones with hydrogen are acid salts. I've seen it a lot, I'm familiar with it, it's not a "concept" at all.

5. Electrolyte and whether it can conduct electricity - it has nothing to do with it! For example, copper wire conducts electricity, but it is not an electrolyte, like calcium carbonate solid does not conduct electricity, but it is an electrolyte. Go look at the definition in the book.

6. The main thing is what I said above: accept the established facts, think less, and remember more. Without enough accumulation, you don't have a "real" problem. Don't be opportunistic, although the words are not good, but learning chemistry is like this!

Thank you for your experience.

Na2O2 is pale yellow, and these physical properties are hard to back.

1. Whether new substances are generated. Anti-non-response is a complex issue.

2. For example, the acid generated after the reaction is unstable and decomposed. There are many factors.

Positive salts such as Na2CO3 na2so4...

Acid salts NaHCO3,,NaHSO4

An electrolyte is a compound that conducts electricity in a solution or in a molten state.

Cultivating interest is key.

1.The products are water, precipitation, and gas, which are metathesis reactions. The rest depends on the entropy change.

2.Metathesis reaction.

3.En. There aren't many high schools with colors. Just remember more.

4.This is the concept in the book.

5.The electrolyte solution will definitely conduct electricity.

6.Read more and remember more.

What is obtained is a hail of vertical salts, and the acid solution is empty.

n(hcl):n(h2o)=:(:5

h2+cl2==2hcl

2h2+o2==2h2o

n(h2):n(o2):n(cl2)=:5:1v(h2):v(o2):v(cl2)=:5:1

b。The direction of the current is from the zinc sheet to the copper sheet After a period of time, the copper ions will precipitate on the zinc and envelop the zinc, so that there is no current.

2.When the masses are the same, m m = n

Same condition and same volume n.

b No, right? Isn't it electrons flowing from the negative electrode to the positive electrode?

C that B is wrong, upstairs says copper wrapping, Cu is insoluble. How to wrap.