Junior high school chemical mass conservation law and chemical equation calculation problems

The balance pointer is biased towards zn.

Because the metal activity of mg is higher than that of Zn, the reaction with HCl solution is stronger, and the reaction between Zn and HCl solution is slow or difficult at room temperature.

The amount of hydrogen released by the reaction of Mg and HCl is more than that of Zn, so the mass of the Mg side is reduced, and the mass of the Zn side is greater than that of the Mg side.

mg+2hcl==mgcl2+h2↑

zn+2hcl==zncl2+h2↑

Because Zn, Mg and dilute sulfuric acid are all equal amounts, it is only necessary to compare the hydrogen produced by the 2 reactions, because the relative atomic mass of Mg is 24, and the relative atomic mass of Zn is 65, that is, 2g of hydrogen is generated for every 24gmg and 2g of hydrogen is generated for every 65gzn, so in the same mass of mg and zn, mg produces more hydrogen, so the balance pointer is biased to the tray where zn is placed.

The relative molecular mass of mg is 24, and the zn is 65, because the same mass and sufficient amount of mg and zn are added, so the hydrogen generated by adding mg is more than that generated by adding zn, and the mg ions and zn ions generated are only converted from the solid state into the solution, and have no effect on the total mass, so the balance pointer is biased to the zn side.

Law of Conservation of Mass:

The law of conservation of mass applies to chemical changes and excludes physical changes.

The law of conservation of mass refers to the conservation of mass and not other aspects.

"Mass" in the law refers to the sum of the masses of the reactants participating in the chemical reaction, not the simple sum of the masses provided.

The mass of reactants and products should include the mass of all substances such as gas and precipitation.

When reviewing the question, it is necessary to pay attention to the key words, such as "full response", "just response", "sufficient response" and other meanings.

The law of conservation of mass is the study of the objective law of chemical reactions from the aspect of quantity, and the process of chemical reactions is the process of recombination of atoms. In all chemical reactions, the type of atoms before and after the reaction does not change, the number of atoms does not increase or decrease, and the mass of the atoms does not change, so the sum of the masses of each substance before and after the chemical reaction must be equal.

Chemical Equation:

1。Understand and master the trimming of chemical reaction equations.

2. Understand the meaning of chemical reaction equations, and be able to read and write chemical reaction equations correctly.

3. The mass ratio between reactants and products can be calculated according to chemical equations.

Least common multiple trimming:

Find the elements that appear once on each side of the reaction formula, and the number of atoms on both sides is more different or the least common multiple is larger as the breakthrough point for balancing.

2.Find its least common multiple.

3.Coefficients are introduced in front of each chemical formula.

Any chemical reaction follows the law of conservation of mass, the mass of the product will be greater than the mass of the magnesium strip because the oxygen in the air participates in the reaction, the sum of the mass of the magnesium strip participating in the reaction and the mass of oxygen participating in the reaction is equal to the mass of the magnesium oxide generated, following the law of conservation of mass of perturbation finger empty, 9, the law of conservation of mass is that the total mass of the reactant is equal to the total mass of the product, and the total mass of magnesium plus oxygen participating in the reaction during the combustion process of magnesium strip is equal to the total mass of the magnesium oxide product. The same goes for phosphorus burning. ,2,Related to valency,2,Wrong!

Said both of them abidingly. The law of conservation of mass is that the total mass of reactants is equal to the total mass of the product. Our old chemistry teasemaker also said it.

I also wish you progress in your studies! 1, they all follow, 1, the principle of the two reactions is exactly the same and both conform to the law of conservation of mass, 1, the law of conservation of mass is that the sum of the quantities of all reactive substances is equal to the sum of the quantities of all the substances generated, since oxygen participates in the reaction, of course, even if the reactants are absolutely in line with the law of conservation of mass, 1, you are mistaken, all follow the law of conservation of mass.

In the future, there will be conservation of energy, conservation of charge and conservation of energy, everything is followed, 0, I want to ask a few questions about the third year of chemistry (about the law of conservation of mass).

1.I know that when the magnesium bar is burning, it has oxygen to participate, so the product will be larger than the mass of the magnesium bar, so it does not follow the law of conservation of mass, but when phosphorus burns, there is also oxygen to participate, why does it follow the law of conservation of mass?

（1）p4 + 5o2 == 2p2o5124g 160g

31g 40g

It happens to react to produce 71g of phosphorus pentoxide.

32g of white phosphorus reacts with 40g of oxygen, and the white phosphorus is excess by 1g, so it cannot produce 72g of phosphorus pentoxide to generate 71g of phosphorus pentoxide, 2) methanol must contain (c, h) elements, and may also contain (o) elements.

3) The mass of carbon dioxide produced is greater than the mass of carbon participating in the reaction, because carbon reacts with oxygen and the CO2 produced is equal to the mass of C plus O2

Carbon is burned in oxygen to produce carbon dioxide, and the mass of carbon dioxide produced is more than the mass of carbon participating in the reaction, because water H2O is generated, and oxygen O2 has no H in it, according to the conservation of elements, methanol contains the H element,

Junior Chemistry - Verification of the Law of Conservation of Mass.

Well, a lot.

Ratio of the number of particles.

The mass of an element.

Elemental mass ratio.

Ratio of the number of atoms.

Material quality. Mass ratio of matter.

Comprehensive calculation problems and so on.

Because of the conservation of mass, the number of atoms is equal before and after the equal sign, so when you seek the chemical formula of Xiangmaozhou, you have to balance it first (generally it is matched before you ask for it, you don't need to match it yourself), and then one by one cross out the existing atoms that are equal to the equal equal to the equal sign, and use the remaining atoms to combine according to the equation.

Let me give you an example: na2co3+bacl

How does baco3 solve the panicle? Observe first removing the atoms that are equal to the left and right of the equal sign, such as.

BA is also crossed out to form Na2CO3+

cl=2co3

I cross out NA2 at the same time for CO3

cl=2 You will find that the remaining atom is only on the left, and you can't cross it out, which is the chemical formula you need.

Let's put it together.

NACL.

I really want to do the equations with the math, you try it.

Conservation of mass is the conservation of molar mass before and after the reaction of a chemical reaction, and the mass is also conserved.

A student used the experiment of the device shown in the figure to verify the conclusion that the volume fraction of the oxygen pants in the air was 21%. Knowing that the volume of air in the bell is as large as the volume of the carrot, how many grams of red phosphorus do you need to hold in the burning spoon?

Because of the conservation of mass, the number of atoms is equal before and after the equal sign, so when you find the chemical formula, you have to balance it first (generally it is matched before you ask for it, you don't need to match it yourself), and then one by one cross out the existing atoms that are equal to the equal equal sign in the remaining atoms, and use the remaining atoms to combine them according to the equation.

Let me give you an example, how to solve na2co3+bacl = 2 +baco3? First, observe the removal of atoms that are equal to the left and right of the equal sign, such as ba.

At the same time, after crossing out Na2CO3 + Cl=2 + CO3, you will find that the remaining atoms are only on the left, and you can't cross them out, which is the chemical formula you need to combine to get NaCl.

I really want to do the equations with the math, you try it.

Generally, the experimental formula is found first, and then the molecular formula is found according to the relative molecular mass. (This is for organic chemistry).

1.For every molecule of methane (CH4), 2 molecules of water (H2O) will inevitably be generated, so the amount of methane = (1 2) * (

By the conservation of mass, the total mass after the reaction minus the mass of methane before the reaction, thus is the mass of oxygen2From the first question, it can be seen that the amount of oxygen (O2) is so the ratio of the amount of methane to the amount of oxygen is: 11

So this reaction equation can be written, for.

6ch4 + 11o2 = 12h2o + 4CO2 + 2CO So the amount of matter that produces CO is.

So the mass of the generated CO is.

A 20 grams, b is 20 divided by 5 and divided by 2, which is 2 grams. From the conservation of mass, C and D are a total of 22 grams, generating 5 grams of D, so generating C17 grams. That is, the mass ratio is 2:17