Wonderful Metals Chemistry of the Fourth Year of Junior Studies

It can only be b's. Fe is less than Zn in the order of metal activity, so there must be Fe. In the case of insufficient and excess Fe, Zn first replaces Cu and then Fe, but because Cu does not react with dilute hydrochloric acid, there is always residual iron; In excess, then the iron will not react at all, only the surplus, the zinc is excessive, and the zinc is also surplus.

In both cases, the copper is completely replaced, both have copper, there is gas produced, there must be iron, the first may not have zinc, the second has, and therefore there may be zinc.

That's right, but there's not necessarily a zn. Zn and Fe replace Cu(2+) at the same time, Zn reacts with Cu(2+) first (this doesn't need to be explained, right?). If Fe reacts first, Zn will also replace Fe(2+), so Zn must react first), and there are 3 possibilities for the remaining solids:

cu；and fe；

fe and zn；

Because there is gas (H2) emitted with HCl, there must be a lively metal, so it can only be 2or 3, to sum up, choose B

First of all, the question does not say that you must add excess iron and zinc, so you should consider the problem into several situations, too much iron, too much zinc, the ratio of the two is just right, both are excessive, you only consider one situation, not comprehensive enough.

The first question is selected C because of the metal activity Mg>Fe>GU If hydrochloric acid can be added to the filtered solid to form bubbles, then there must be Fe, and if there is Fe, then all the GU in the solution will be replaced with Fe. However, it is not possible to determine whether mg is present in the solid, nor is it possible to determine whether FeCl2 is present in the solution.

The second question is C because it is always biased to the left. So the left side is heavy. So the hydrogen on the right is generated quickly and abundantly.

To generate an H requires Al27 3 Fe56 3 needs Zn65 2, Minghu Juexian puts the same quality of Al, pants and Fe to generate hydrogen, natural Al+sulfuric acid Zn>Fe; Therefore, the wrong choice is faster than FE in ZN.

Solution: Let g zinc react with sulfuric acid of mass x to generate zinc sulfate of mass y and hydrogen of mass z.

zn ＋ h2so4 ＝ znso4 ＋ h2↑13g x y z

65∶98＝13g∶x x＝

Before the reaction, the solute fraction in dilute H2SO4 was -x100%65 161 13 y y

65∶2＝13g∶z z＝

The mass of the resulting ZnSO4 solution is 13 g + 100 g - or g

The absolute mass fraction of dissolvin was -x100%.

Answer: The mass fraction of the solute in the dilute sulfuric acid is, and the mass fraction of the solute in the solution obtained after the anti-solanine response is.

100g of this sulfuric acid solution is diluted into 10% sulfuric acid, and water x grams need to be added?

100× 10% x=96g

Add 96 grams of water.

At 20, in 100g of 10% salt water, add 1g of potassium chloride, then potassium chloride can be dissolved, the solution is a saturated solution for salt. For potassium chloride it is an unsaturated solution. The mass fraction of the pure mold of table salt in the solution becomes smaller The specific calculation formula is 100*10%) 100+1)*100%=The mass fraction formula of potassium chloride in the disturbance solution is 1 (100+1)*100%=

A: It must contain charcoal powder and iron oxide, it must not contain copper oxide, and it may contain calcium carbonate.

Analysis: Write down the chemical formulas of the four substances: C, CaCO3, Cuo, Fe2O3.

When the sample is heated to high temperature, the following reactions may occur: high temperature = Cao + CO2; High temperature = CO2 +2Cu; High temperature = 4Fe + 3CO2. Therefore, the remaining solids may have cao, cu, fe.

After cooling, a sufficient amount of dilute hydrochloric acid is added to the remaining solid, and all the solids in Zhuzhou (1) are dissolved, indicating that there is no Cu in the remaining solid (it is ranked after hydrogen in the active table and cannot react with dilute hydrochloric acid), so there must be no CuO; (2) At the same time, a flammable gas is generated, indicating that there is Fe in the remaining solid (which is ranked before hydrogen in the activity table, and can react with dilute salt to form hydrogen gas), so there must be Fe2O3 and C (there can be no C, because without C, Fe cannot be generated, and flammable gas will not be produced).

CaCO3 may be present because its presence or absence does not affect the results.

Therefore, the residue must contain charcoal powder and iron oxide, must not contain copper oxide, and may contain calcium carbonate.

It must contain charcoal powder and iron oxide, and it must contain copper oxide and may contain calcium carbonate.

The flammable gas is produced, it can be known that the gas must be hydrogen, and there may only be two metal elements of iron and copper in the mixture, and copper does not react with dilute hydrochloric acid, only iron reacts with hydrochloric acid to produce hydrogen, so after heating, the solid produces iron-hungry elemental substances, so there must be charcoal powder and iron oxide in the substance, because the reduction of iron is stronger than copper, assuming that there is copper oxide, carbon should first react with copper oxide and then react with iron oxide, and iron element can be produced in the solid, then copper oxide and carbon must react completely, and copper does not react with dilute hydrochloric acid, so there will be no complete dissolution of the solid mentioned later, so it does not contain copper oxide. And because carbon and iron oxide can react to produce carbon dioxide, it is not certain that there is calcium carbonate, but calcium carbonate produces calcium oxide after heating, which can be dissolved in dilute hydrochloric acid, so calcium carbonate cannot be ruled out, so there may be calcium carbonate.

Charcoal powder, iron oxide is there.

Copper oxide none.

na2co3+2hcl=2nacl+co2↑+h2ox y

Get x= y=

NaCl mass =

The quality score is:

During the formation of stalagmites and filotic stalactites, the following two reactions will occur when the open and vertical collisions occur:

CaCO3+CO2+H2O=Ca(HCO3)2 (Synthetic Radical Response).

Ca(HCO3)2 = CaCO3 +CO2 + H2O (decomposition reaction).

Huhu: I'm in my third year of high school, and I still remember this question, the classic question type of the fourth year of junior high school.

Well. After adding 50g of hydrochloric acid for the second time, compared with the first addition of dilute hydrochloric acid, the total mass of the beaker and the reaction after the reaction increases, according to the reaction equation, you think, if the carbon dioxide does not come out and is still in the beaker, then the total mass should increase by 50g, but it is precisely because of the carbon dioxide gas that the total mass only increases, so the tomb is taken to the foot of the year, m (carbon dioxide) =

Then, because the solid mixture was sufficient in the first reaction, all the hydrochloric acid participated in the reaction, and the carbon dioxide released by the finch should also be there.