Chemistry experts junior high chemistry problems

Although there will be a sequence in the chemical reaction, no matter what the reaction sequence is, it will be reflected by the strong performance of the substance in the end, so you just need to remember the strength of the substance, just like this belongs to the problem of acid-base neutralization, the alkaline substance is Ca(OH)2, and the acidity is H2CO3 and hydrochloric acid, so for the comparison of acidity, hydrochloric acid is significantly stronger than H2CO3, so it will eventually become a salt in the form of CaCl2. For the process, it will be a staggered reflection of a variety of substances (Ca2+, Cl+, OH-, CO32-, HCO3-, H+,), but the essence of the chemical reaction is the gain and loss of electrons, so it will eventually be related to the material with strong electron gain and loss ability, a bit like the usual metal replacement reflection, no matter what kind of metal salt is generated, it will be replaced by the metal that is more active than the salt metal, in essence, that is, the strong activity of the metal has a stronger ability to lose electrons, or the electronic ability is weaker. The electrons are attracted to the metal ions in the salt metal and are reduced, so grasp the essence of everything, and you can respond to all changes with the same, understand, if you don't understand, I can come to me, and we can communicate together.

In fact, none of these questions reflect the specific situation. If it is a sufficient amount of clarified lime water, it will definitely get turbidity in the end, which can be regarded as precipitation. As long as the gas mixture can exist in lime water for a long enough time (i.e. lime water depth is enough).

For the reaction sequence question you asked, in fact, during the operation, it will react, but the phenomenon may be different depending on the concentration and dosage, because the ions are uniform in the solution, and if you add the mixture, then the ions will definitely react with A and B at the same time. As for the possibility that a reaction product may disappear again in the end, it is also a reaction, but the product reacts with other reagents immediately, what do you think?

HCl reacts with Ca(OH)2 in clarified lime water to form CaCl2 and water, and also reacts with CaCO3, the product of Ca(OH)2 and CO2 reaction, to form CaCl2, water and CO2

So no precipitation is generated.

Intermediate reactions, do not have to be taken into account.

Only the initial reactant and the final product need to be considered.

CO2 and sufficient amount of clarified lime water reflect the production of CaCO3, HCL and CaCO3 reflect the production of calcium chloride, the neutralization reaction you said is an intermediate reflection, do not need to be considered.

The intermediate process does not need to be considered, only the product produced needs to be considered, and the product produced cannot be reflected with the reagent in it

It is true that CO2 and Ca(OH)2 produce CaCO3 precipitation and HCl reacts neutralization with Ca(OH)2, but.

Let the mass of the iron consumed by this reaction be x, and after the equation, it can be seen that the mass of copper can be expressed by 64x 56, and because the total solid mass after the reaction is 108 grams, the mass of copper can be expressed by 108-100+x (where 108-100 is the excess mass, and x is the mass of iron converted into copper), so the equation 108-100+x=64x 56 can be listed, and the mass of iron obtained is 56 grams, so the mass of copper is 64 grams.

With the difference method, the solids increased by 108-100 = 8g

The difference between 100 grams and 108 grams is 8 grams, so the difference between the atomic mass of iron and copper is calculated to be 8, so the mass of copper is equal to the relative atomic mass of copper 64

Zn+2HCl=ZnCl2+H2 Hydrogen is generated by the reaction of Zn and hydrochloric acid, the mass of Zn is calculated first, and the mass of copper = 20g-Zn

Only zinc and hydrochloric acid react, and the mass of zinc can be calculated according to the equation, and then it can be subtracted.

Solution: Let the mass of copper in the sample be x, then the mass of zinc is 20g-x

zn + 2hcl=zncl2 + h2↑65 220g-x

__= __20g-x

x = g A: The mass of copper in a 20g brass sample is.

I'm a chemistry teacher. ）

First of all, we can know from the options that the mixture is all carbonate and can react with dilute hydrochloric acid, and here we can set the reaction equation as.

mco3+hcl===mcl+co2^

x 4410g

Note: The valency of m is independent of the production of carbon dioxide), below, we can find the average relative molecular mass of the mixture according to the equation: x=100

In the end, we judge according to the options:

a: The relative molecular weight of potassium carbonate is 138, and that of magnesium carbonate is 84; The average molecular weight after mixing can be 100, so the answer A is correct;

B: Sodium carbonate is 106, calcium carbonate is 100, and it is greater than 100 after mixing, and B is wrong;

C: magnesium carbonate is 84, barium carbonate is 197, mixed can be equal to 100, C pair;

d: Sodium carbonate is 106, potassium carbonate is 138, and it is greater than 100 after mixing, and D is wrong.

To sum up, the answer is a c

a、cm ~ co2

x 4410g

Then the average relative molecular weight of the mixture M is 100, the relative molecular weight of potassium carbonate in A is 138, and the relative molecular weight of magnesium carbonate is 84, which can be 100 after mixing, so A is correct;

The relative molecular weight of sodium carbonate in b is 106, and the relative molecular weight of calcium carbonate is 100, which is greater than 100 after mixing, so b is wrong;

The relative molecular mass of magnesium carbonate in c is 84, and the relative molecular mass of barium carbonate is 197, which can be equal to 100 after mixing, and c is correct;

The relative molecular weight of sodium carbonate in d is 106, and the relative molecular weight of potassium carbonate is 138, and if it is greater than 100 after mixing, D is wrong.

10 g of potassium carbonate produces 10 138 44 = carbon dioxide.

10g of magnesium carbonate produces 10 84 44 = carbon dioxide.

10 g of sodium carbonate produces 10 106 44 = carbon dioxide.

10 g of calcium carbonate produces 10 100 44 = carbon dioxide.

10 g of barium carbonate yields 10 197 44 = carbon dioxide.

The carbon dioxide produced by the two substances in the mixture should be greater than, less than, or both equal to AC

Extreme Hypothetical Method.

1. Assuming that the mixture is all potassium carbonate, it can be known from the reaction ratio that potassium carbonate is required 2, assuming that the mixture is all calcium carbonate, it can be known that calcium carbonate is required here 3, assuming that the mixture is all barium carbonate, barium carbonate is required here.

4. Assuming that the mixture is all sodium carbonate, sodium carbonate is required here.

5. Assuming that it is all magnesium carbonate, magnesium carbonate is required here.

Since there is only one mixture, then the composition of the mixture should be one larger than the other smaller, here both a and c are satisfied.

a.Mass may be produced when potassium carbonate (relative molecular mass 138) and magnesium carbonate (relative molecular mass 84) are mixed.

b.The mass of sodium carbonate (relative molecular mass 106) and calcium carbonate (relative molecular mass 100) must be less than when mixed.

c.Magnesium carbonate (relative molecular mass 84) and barium carbonate (relative molecular mass 197) may be mixed to produce mass.

d.Sodium carbonate (relative molecular mass 106) and potassium carbonate (relative molecular mass 138) must be less than when mixed.

So the final answer is: AC

In both cases, either two substances with the same mass produce the same mass of CO2 of the same mass, or one produces more or less CO2. Note: The calculation process is assumed to be 100g, and then calculated. For example:

A potassium carbonate 100g calculates the mass of a CO2, and then magnesium carbonate 100g calculates the mass of a CO2, and then according to the previous comparison.

Using the average mass method to calculate, assuming that this mass is of a certain substance, calculate its relative molecular mass, and then calculate its average value, one is greater than the average, the other is less than the average, only in this way can the average value be reached.

The average molar mass of carbon dioxide, i.e. the mixture, is 100 g molComparison can know the choice of CD