Chemistry problems for junior high school and senior high school solving, chemistry problems for jun

Gas sample of nitrogen in STP volume. How many moles of nitrogen are present? In STP calculate all molecules for each GASWS below.

a. b. c.

H2O2 N2 4 g. Calculate all the volumes in each of the following GASWS at STPA. g CO2 B

g chlorine c ch4 5。The density (density) of the sample gas is in the STP.

Determine its molar mass (molar mass)6. What quality does he ask for in the balloons that he fills in the STP? (he-4) Student Question 2 The first question is like this.

The first question I don't understand what the rest is, I'll give you the formula, you set yourself n=m m n=n na n=v vm your first question, which vitamin is abcdef vitamin ac20h30o vitamin b does not get vitamin cc6h8o6

Vitamin D doesn't have Vitamin EC29H50O2 That's all I can help you with. I tried my best, but you really don't understand the question

25 grams of 20% dilute hydrochloric acid, the mass of HCl can be calculated, and thus the mass of Cl can be calculated, and the mass of R can be calculated.

25*20%=5g(

In fact... It's better to divide more.

So many questions.

3.Solution: Let the mass fraction of m in the sample be x

m(cl)=m*w%*m(cl)m(hcl)=25*20%*

Because the mass of chlorine is conserved, m(cl) in the salt = the metal contained in the salt.

So 5x=,x=97%

The mass fraction of m in the sample was 97%.

4.Analysis: According to the principle of average value, to make a mixture of two metal powders 6 grams, add a sufficient amount of dilute sulfuric acid to produce hydrogen, then the two metals contained in the sample, when the mass is 6 grams, the mass of H2 produced should be greater than one gram and less than one gram, only in this way, when the two metals are mixed, when the mass is 6 grams, the mass of H2 produced by the mixture may be exactly grams.

According to the relevant reactions, the mass of H2 produced by Zn was less than that of gram when the mass was 6 grams, and the mass of H2 produced by Fe, Mg, and Al was greater than that of gram when the mass of Fe, Mg, and Al was 6 grams. CU does not react with dilute HCI.

So choose B5The mass of hydrogen produced is.

The mass of dilute sulfuric acid that consumes 30% is about.

7.Mass fraction of hydrochloric acid solution Mass fraction of the solution obtained after the reaction (What should be done at room temperature?) What are you going to do? becomes an unsaturated solution. Add water.

My answer.

Hydrogen gram is, need, then every 1mol of hydrogen needs alloy 34g2al 3h2 alloy 18g of aluminum per 1mol of hydrogen generated;

mg H2 requires 24g of magnesium per 1mol of hydrogen produced

2Na H2 requires 42 gFe of sodium per 1 mol of hydrogen and 56 g of iron per 1 mol of hydrogen produced

Cu H2 requires 64g of copper per 1mol of hydrogen generated

Zn H2 requires 65g of zinc per 1mol of hydrogen generated

a.18g of aluminum, 24g of magnesium, and the average mass of orange is less than 34g, which does not meet Zheng Zhi;

b.sodium 42g, iron 56g, average mass greater than 34g, does not meet;

c.18g of aluminum, 64g of copper, and 34g of Wu grip are in between, and it may be a combination of the two;

d.Zinc 65g, magnesium 24g, 34g in between, it may be a combination of the two;

Choose two CDs.

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.

Quality of HCL =

The mass of which contains the cl element =

According to the law of conservation of mass, after the reaction of metal with hydrochloric acid, all metal elements form cations in chloride, so the pure metal mass =

The quality score is =

Let this nitric acid volume be 1 l

The mass is 1000*

Contains 1440* of HnO3

After adding the same volume of water, the mass becomes 1440 + 1000 = 2440g, so the mass fraction is 1008 2440 * 100% = so choose c

The answer is A, calcium chloride.

It can be analyzed and solved by the equation, and if all grams are NaCl, then its products should have grams;

In the question, the amount of production is as bad as the amount of boring;

According to the principle of averages, there should be a substance with an output greater than that sandwiched in it, and the equations for the four species can be solved if 5. If the hood lacks 85 grams of calcium chloride, its yield is grams.

So, the answer is a

If all the samples are sodium chloride, silver chloride will be generated.

Now the orange is erected into grams, indicating that it contains chloride with a smaller molecular weight than NaCl.

So there is no answer.