I don t know much about chemistry in the third year of junior high school, so I ask everyone!

Reactions between solutions require a significant reduction in ion concentration. That is, the formation of precipitated gases or water or complexes.

Dissolve or not dissolve you will be solubility ** Okay, generally the product has at least one insoluble.

Generally, the stronger acids can be replaced with K Ca Na mg al zn fe sn pb to produce hydrogen, but the first few are reacted with water.

Bases can react with NH3.

Color = = I found out.,You're personal.,What are you doing in class.。

Copper ions blue.

Iron ions reddish-brown.

Ferrous ions: light green.

Check it yourself, it's brain-dead, if my teacher goes up, I'll hack you to death. Reward!

You can summarize this, borrow notes from your classmates or teachers, and look at them. Understanding is more important than anything else.

It is regular reactants are insoluble to form slightly soluble substances The product can have one of them insoluble hydrochloric acid and active metals react to form bubbles Have you ever memorized the order of metal activity Hydrogen replacement before hydrogen is that the one in front of hydrogen can react with acid to replace the metal behind it and copper, silver and gold cannot react with hydrochloric acid or sulfuric acid There will be no bubbles. You have to carry it, copper is red, iron is silvery-white, iron oxide is black, ferrous chloride is light green, ferric chloride is pale yellow, you can see one on the back. I am also a student who is about to graduate from junior high school, study chemistry hard, it is not difficult, you have to listen carefully in class, I wish you success.

The combination of equations is regular, for example, in the metathesis reaction, the anion and ion are exchanged to form the corresponding substance, one of which is either carbonic acid continues to decompose into water and carbon dioxide, or hydrogen ions combine with hydroxide to form water, or it is a precipitate, such as NaOH + HCl = NaCl + H2O AGNO3 + HCl = AGCL (precipitation) + HNO3, etc.

Chemical reactions are regular, for example, the displacement reaction is one element and one compound to produce another element and another compound. Another example is the metathesis reaction, which is the exchange of anions and cations between two compounds to form the other two compounds, in which the product must have at least one refractory electrolyte (in junior high school, it can be simply recorded as the generation of water or precipitation or gas), such as HCl+NaOH=NaCl+H2O acid, which can react with active metals to form hydrogen, which has potassium, calcium, sodium, magnesium, aluminum, zinc, iron, tin, lead. Metals tend to be silvery-white, but copper is brownish-red and gold is golden-yellow.

It seems that there are these two metal colors that need to be remembered.

1. There are 4 substances in a closed container. They react fully under certain conditions, and the mass of each substance before and after the reaction is measured as follows:

Substance x y z q

Pre-reaction mass g 4 6 1 20

The post-reaction mass g 0 6 13 to be measured.

The relative molecular mass of X is known to be n, and the relative molecular mass of q is 2N. Fill in the following blanks accordingly:

1) What is the mass of q after the reaction?

To be measured =4+6+1+20-0-6-13=12

2) What is the ratio of the stoichiometric number of the chemical equation x to q for this reaction?

4-0)/n]:[20-12)/(2n)]=1:1

2. A substance R is burned in pure oxygen to produce and, and the inference for the composition of the substance R is:

1) How many elements are in substance R?

Contains carbon and hydrogen, so the substance R only contains carbon and hydrogen elements.

2) What is the chemical formula of substance R?

The ratio of the number of atoms of substance r containing only carbon and hydrogen is (:4

So the chemical formula of the substance R is CH4

1,。（1）q=12 (2) x:q=1:

1 2.(1) c, h (2) h20 i.e. h atom o atom c in the substance r c:h=1:

4 Chemical formula: CH4

q = 20 + 4-13 = 11, also reactants.

1) The mass of q after the reaction is 11.

2) The ratio of the stoichiometric number of the chemical equation x to q of the chemical equation of the reaction = 2 * 4: 9 = 8: 9.

Medium gram, gram; Contains grams, contains grams, grams + grams = grams.

Therefore: (1) Substance R contains only two elements, C and H.

2）c：h=：:4。The chemical formula of the substance R is CH4

.The overall mass conservation after the reaction is 4+6+1+20-6-13=12 The mass of Q is 12g

X is 4g, q is 8g, and because the relative molecular mass of q is exactly twice that of x, the amount of substances involved in the reaction x and q is the same, and the mass ratio of 1:1 is 1:2

The mass of q after the reaction of 1 (1) is (4+6+1+20)-(0+6+13)=12g

2) x:q=4*n:20*2n=4n:40n=n:10n2 (1) Contains C and H elements.

2）。。No, it won't.

1. (1) The mass of q after the reaction is 12, according to the law of conservation of mass, the mass before and after the reaction remains unchanged, so (4+6+1+20)-(0+6+13)=12

2) The chemical equation of the reaction is that the ratio of the stoichiometric number of x to q is twice the relative molecular mass of 3 and the mass of q is 3 times the mass of x during the reaction, and in order to achieve equilibrium, the ratio of the stoichiometric number of x to q is 3 2.

2. (1) Substance R contains two elements. c and h

2) The chemical formula of the substance R is CH4are converted to mol calculations, and they can be obtained.

1) What is the mass of q after the reaction?

20-m+4=12

m=122) What is the ratio of the stoichiometric number of the chemical equation x to q for this reaction?

nx+mq=z

nn 2mn

nn:2mn=4:12

n:m=2:3

The ratio of the stoichiometric number of x to q is 2:3

2. A substance R is burned in pure oxygen to produce and, and the inference for the composition of the substance R is:

1) How many elements are in substance R?

C-containing mass = H-containing mass =

Therefore, the substance R contains the elements C, H, and O.

2) What is the chemical formula of substance R? Please write out the process.

The ratio of the number of elements containing C, H, and O in substance R is:::16:1 The chemical formula of substance R is C8H16O

1. X decreases after the reaction, so it is a reactant, and Y does not change before and after the reaction, so it is the catalyst Z that increases after the reaction, so it is a product, q=20+4-13=11, which is also a reactant.

1) The mass of q after the reaction is 11.

2) The ratio of the stoichiometric number of the chemical equation x to q of the chemical equation of the reaction = 2 * 4: 9 = 8: 9.

2. Medium grams, grams; Contains grams, contains grams, grams + grams = grams.

Therefore: (1) Substance R contains only two elements, C and H.

2）c：h=：:4。The chemical formula of substance R is CH4, methane.

All written by myself, correct answer:

1.For a long time, scientists believed that noble gases do not react chemically with any substance, and called noble gases "noble gases", which has constrained the study of the chemical properties of noble gases for a long time. In fact, noble gases can react with other substances to form some noble gas compounds, which are not required to be mastered in middle school.

2.The method is to put the burning sticks into the mouth of the gas collection cylinder containing the three gases, and the sticks burn more violently in the oxygen, but continue to burn in the air, and extinguish the sticks in the nitrogen. In this case, nitrogen is often replaced with carbon dioxide.

It is important to remember not to use spark-bearing sticks to identify these three gases, because spark-bearing sticks will soon be extinguished in the air, so it is not easy to distinguish between air and nitrogen.

3.Oxygen is an oxidant, you can understand it as an accelerant in junior high school, and combustibles are oxidized and exothermic by oxygen to cause combustion, so oxygen cannot be used as fuel, yes"Substances that support the combustion of combustibles"。

The general knowledge of geography about environmental protection is mentioned in chemistry textbooks.

5.Because the temperature of the flame is different at different positions, the outer flame is higher than the inner flame and higher than the flame center, so the result is that the test tube bursts due to uneven heating. The correct way is to move the test tube back and forth on the outer flame of the flame to heat it evenly, and then use the external flame of the alcohol lamp to concentrate the heating at the position that needs to be heated.

6.The reason why carbon dioxide makes the clarified lime water turbid is that the carbon dioxide reacts with the solute calcium hydroxide of the lime water to generate water and calcium carbonate precipitation, the calcium carbonate precipitates are white, and the precipitation is suspended in water, which is manifested as the clarified lime water becomes turbid, and the reaction equation is Ca(OH)2+CO2=CaCO3(precipitation)+H2O, because the precipitation is white, it is said that a white solid is generated, and the suspended white solid is the reason why the lime water becomes turbid, that is, the white solid and turbidity are essentially the same.

I'm so tired, I hope it can help you

1.Xenon can react with fluorine to form xenon tetrafluoride (special case) XEF42The wood strips are more vigorous for oxygen, unchanged for air, and extinguished for nitrogen. (Oxygen fuels the flame more vigorously, nitrogen does not support combustion).

3.Oxygen is a combustible and cannot be used as fuel.

The reasons are slightly ......）

5.Explosion (uneven heating, different temperature of internal and external flames, high outside and low inside) 6The reason for the turbidity is the production of calcium carbonate, which adheres to the wall and bottom of the bottle. Open! The turbidity occurs because the solution is not standing, and the calcium carbonate particles are suspended in the water.

1.Xenon and fluorine can react with XEF6

And PTF6

2.The burning wooden strips are put into three glass bottles containing the same volume of gas in turn, and the nitrogen gas cannot make the wooden strips continue to burn, and the air and oxygen can support the continuous burning of the wooden strips, but the combustion time of the equal volume of air is shorter than that of the same volume of oxygen, because there is not only oxygen but also CO2 in the air, so the three gases can be identified.

3.Oxygen is only an accelerant, not a fuel, it can only support combustion, and it cannot spontaneously combust itself.

The test tube will rupture because the alcohol wick is an internal flame and its temperature is very high.

6.The white substance is calcium carbonate because calcium hydroxide reacts with carbon dioxide to form a white calcium carbonate caCO3 precipitate.

I don't understand hi me o( o

1.Xenon and fluorine can react under certain conditions to form xenon tetrafluoride.

This question is very out-of-the-box! ）

2.Stick a burning wooden strip into each of the three gases.

Burns more vigorously - oxygen.

The combustion situation remains the same - air.

Burning sticks extinguish – nitrogen.

3.No. Oxygen is flammable, but not flammable. So oxygen can be used as an accelerant, but not not.

as fuel. Because vegetation has the effect of fixing sand and blocking sand.

This question is obviously a biology and geography question! ）

5.The test tube bursts due to uneven heating.

6.Calcium carbonate. Carbon dioxide + calcium hydroxide = calcium carbonate.

Please don't copy and paste! Plagiarism is shameful! Original !! by Michael Young

1.I don't know if I don't learn rare gases in the third year of junior high school.

2.Put the burning wooden strip into a gas collection cylinder with three kinds of gases, and the wooden strip in the air can burn for a while; The sticks of wood in the oxygen will burn more violently; The nitrogen will be extinguished immediately. (There is some oxygen in the air; Oxygen is pure oxygen; Oxygen-fueled; Nitrogen does not support combustion).

3.No. (Oxygen fuels but does not burn).

Plants have the role of fixing the soil and can maintain soil and water).

5.The test tube ruptures. (The alcohol lamp core has the highest temperature, which is easy to rupture the test tube.)

6.Because of the white solid material that appears on the wall and bottom of the bottle, the lime water becomes cloudy. The white solid is calcium carbonate.

CO2 + Ca(OH)2 = CaCO2 + H2O, that is, carbon dioxide plus calcium hydroxide (lime water) is equal to calcium carbonate (CaCO2) plus water (H2O).

1.Xenon and fluorine can react under certain conditions to form xenon tetrafluoride.

2.It is unchanged in the air, extinguished in nitrogen, and more vigorous in oxygen.

3.No, it is not flammable, it is combustible.

Trees can block wind and sand.

5.The temperature of the inner flame is not as high as that of the outer flame, resulting in uneven heating and bursting of the test tube.

6.Calcium carbonate is insoluble and a white solid.

1: Chlorine. 2: No change in air, re-ignition in oxygen, extinguishment in nitrogen.

3: Yes. 4：a

5: The alcohol lamp is turned off.

6: Precipitated calcium carbonate.