Chemistry questions about the law of conservation of mass

It turned out that the balloon was deflated.

Later, hydrogen peroxide reacted under the catalysis of manganese dioxide to produce oxygen.

Determine point 1: According to the law of conservation of mass, the airtightness of the reaction vessel is intact and its mass does not change.

Why is the balance uneven?

Because after the oxygen is generated, the balloon changes from deflated to bulging, and is subjected to the upward buoyancy generated by the air.

As a result, the pressure of the reaction vessel on the balance tray decreases.

So the scales are unbalanced.

The point is that the balloon is buoyant by the air.

I guess I understand.

The experiment was a failure because the reaction and device chosen were not suitable to prove the law of conservation of mass.

The reason for the failure of this experiment is that hydrogen peroxide produces oxygen under the action of manganese dioxide as a catalyst, and this set of devices is sealed, so the air pressure in the Erlenmeyer flask becomes larger, and the balloon rises, which produces air buoyancy as mentioned in the previous two, so the whole set of devices is subjected to two forces gravity and buoyancy, and the pressure of the Erlenmeyer flask on the tray becomes smaller, so it is unbalanced.

The experiment did not fail, because the balance was unbalanced because the hydrogen produced was less dense than air, so that the Erlenmeyer flask had an upward buoyancy to say that the balance was unbalanced.

First know that water has a-b g h2o know:

Then there are 16 18 for oxygen, i.e. 8 9 * (a-b) and hydrogen 1 9 (a-b).

There are b grams of gas left in the container, and I don't know what kind of gas it is, so there are two situations:

b g gas is oxygen: then: oxygen 8 9 * (a-b) + b, hydrogen has 1 9 (a-b).

Analyze another situation in the same way.

1. The law of conservation of mass means that in a chemical reaction, the sum of the masses of the substances participating in the reaction is equal to the sum of the masses of the substances formed after the reaction. The root cause is explained from a microscopic perspective: before and after a chemical reaction, the type, number, and mass of atoms remain unchanged.

2. Understanding of the law of conservation of mass.

1) "Chemical reaction" is the premise. The scope of application of the law of conservation of mass is chemical change, not to physical change, and any chemical change follows the law of conservation of mass.

2) "Participation in the reaction" is the basis. The concept clearly states that it is the sum of the masses of the substances that "participate in the reaction", and the mass of substances that do not participate in the reaction cannot be counted.

3) "Sum of Quality" is the core. Whether it is a substance participating in the reaction or a substance formed after the reaction, no one should be missed when calculating the leakage.

4) "Conservation of mass" is the goal. The law only applies to the conservation of "mass", excluding the conservation of volume and the conservation of the number of molecules.

（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.

It is reducible, and after reacting with copper oxide, carbon dioxide is generated, which means that the original carbon element will completely become carbon dioxide. As the title suggests, the original carbon element has grams, and the grams of c correspond to them, that is, carbon dioxide will be introduced into the solution, and after complete absorption, it will increase the mass.

2.This question is the same, first through copper oxide, hydrogen becomes water, carbon monoxide becomes carbon dioxide, carbon dioxide is absorbed, then that is, the mass of lime water increases, and then the proportion of carbon is calculated according to the proportion, and then the mass of carbon monoxide is calculated, and finally the mass of hydrogen is calculated, and the proportion is found.

1.Conservation of mass.

c is eventually converted to CO2, and then the c element is converted to caco3...Hit.

c~~~caco3..

10g*36%

x==30g

2.After drying, there is only CO2, which reacts with lime water.

The mass of the CO2+Ca(OH)2 CaCO3 H2O solution was reduced by 44 100 56x

Correspondence with CO quality.

Mass of H2 and CO in the original gas mixture: 7

There is carbon in 1:10g, and the mixture is heated in copper oxide and becomes carbon dioxide, and the carbon is mo, that is to say, there is carbon dioxide later, and the molar *** of calcium carbonate precipitation is like 100g mol, 100*

So there is 30g of precipitation.

2: The less mass is calcium carbonate precipitation. Namely.

Therefore, after drying, the gas is carbon dioxide, and the original carbon monoxide is also carbon dioxide, and the mass is ......Do the math.

I was in a hurry to leave ......Excuse me.

Analysis: (1): This problem uses the conservation of carbon to calculate: the mass of carbon in 10g of mixed gas is 10*36%=

The amount of matter is: from the chemical equation of the reaction between carbon monoxide and copper oxide, it can be seen that the carbon in carbon monoxide is converted into carbon dioxide without loss, and the carbon dioxide generated is the home of carbon dioxide and carbon dioxide in the original mixed gas, and the carbon is all transferred to calcium carbonate when it reacts with calcium hydroxide, so the mass of calcium carbonate is.

2): This question is still calculated by using the conservation of carbonic acid, the amount of reduction is the amount of calcium carbonate, and the amount of calcium carbonate is about, so the carbon in calcium carbonate is, and these carbons come from carbon monoxide, so the mass of carbon monoxide is:

Then the mass of hydrogen is:, so::7

Method 2: CO2+Ca(OH)2 CaCO3 H2OδM44

x = the amount of carbon dioxide in the substance: , so the mass of carbon monoxide for hydrogen is:::7

Equally, of course! The precondition for the law of conservation of mass in chemistry is the trim equation.

Six unchanged:

Macro: 1The total mass of the substance before and after the reaction is unchanged.

2.The type of element remains the same.

3.The total mass of the element does not change.

Micro: 3The type of atom does not change; 4.The number of atoms does not change; 5.The mass of the atom does not change.

Two must change:

Macro: A change in the type of matter.

Microcosm: The way the particles of matter are made up must change.

Two possible changes:

Macro: The valency of the element may change.

Microscopic: The total number of molecules may change.

The ratio is 3:2

For the first time, all reactions are given to b to y g and a to x g because c is 15 g done

Conservation of mass x+y+15=30

x=15-y, so the ratio of a to c participating in the reaction is (15-y) 15, according to the first word, the first a is 15g, the reaction is 15-y, is not the remainder, and the mass of a participating in the second reaction is 15-(15-y)=y g, and the second time 10gc is added, and the remaining a is consumed.

So find another The ratio of a to c participating in the reaction is = y 10, and the ratio of a to c should be the same for each reaction, which is (15-y) 15 = y 10 to get y = 6 g

X=9 g is obtained from x=15-y

So the mass ratio of a to b participating in the reaction = 9 6 = 3:2

Contains carbon and hydrogen.

The ratio of the number of atoms containing oxygen c, h, and o is (:(4:1

So choose B and wish you a happy new year.

Solution: First calculate the mass of carbon contained in carbon dioxide: grams).

Then calculate the mass of hydrogen contained in the water: grams).

The total mass of carbon and hydrogen is grams).

The mass of organic matter a is grams, which means that in addition to carbon and hydrogen, there are also oxygen elements, grams) The ratio of the number of carbon, hydrogen and oxygen atoms is: (:4:1, so the correct answer is: b

That is, 32g of organic matter produces CO2 44g and H2O 36g can judge that oxygen is 80-32=48 oxygen and 32g can be consumed.

Oxygen, a16g-2mol is not right.

True, not true. d。。。So choose B

It can be seen from the complete reaction that the ratio of CH is 1:4, then A or B, and then according to the knowledge, A is selected, CO2 is generated, and B is selected, and the CO2 generated is just right.