Grade 3 Chemistry uses simple calculations of chemical equations.

1. According to the reaction CaCO3+2HCl=CaCl2+H2O+CO2, only CO2 is a gas, so the reduced mass is the mass of CO2, and the mass of calcium carbonate in limestone can be set to x, then.

caco3+2hcl=cacl2+h2o+co2↑*x***

100/x=44/

x=10g, so the mass fraction of calcium carbonate in limestone is 10

1) The equation of the chemical reaction that occurs is 2kclo3 = mno2 = 2kcl + 3O2, and there is only O2 gas in the product, and the mass of O2 can be known according to the conservation of mass.

2) After the reaction is complete, Kclo3 is completely decomposed into Kcl, and Mno2 is the catalyst, and the mass remains unchanged before and after the reaction. Therefore, the remaining solid contains KCl and Mno2. Let the mass of KCL be x, then.

2kclo3=mno2△=2kcl+3o2↑**x***

149/x=96/

x=mno2 has a mass of .

Therefore, the remaining solid contains KCl and Mno2.

The reduced mass is carbon dioxide, so the original calcium carbonate, 10g, the percentage is 80% The changing mass is oxygen, which corresponds to oxygen, which corresponds to potassium chlorate, and the remaining manganese dioxide, potassium chloride = -

Let's put it this way, looking at the proportion of atoms and molecules in the equation.

In the first question, 1mol of calcium carbonate produces 1mol of carbon dioxide, in the second question, 1mol of oxygen corresponds to 2mol of oxygen atoms, and every mol of potassium chlorate reaction will release 3mol of oxygen atoms, so every 3mol of oxygen corresponds to 2mol of potassium chlorate, and the rest is a simple mathematical calculation.

The salt is sure when CaCO3 can be reacted with HCl to form CO2. Writing the reaction equation shows that CaCO3 and CO2 are 1: the relationship between Crypto Zen 1, and the mass of CaCO3 can be calculated by CO2.

In calculating the mass of ca in caCO3 is (40 100)*. So the mass fraction of the ca element is:

1 All Zn+2HCl=ZnCl2+H2

x yx= y=

Hydrogen that can be produced.

The quality of zinc chloride.

zn+2hcl=h2+zncl2

Then it will be calculated accordingly, and it will not be known whether the relative atomic mass of zn is remembered correctly or not.

Let the mass of the generated zinc chloride be x and the mass of hydrogen be y. (relative atomic mass zn: 65 ci: h:1) then:

zn+2hci=znci2+h2!

65 Solution x=

y=A:....

(1) The quality of the water consumed by electrolyzed water.

2H2O = Electrolysis = 2H2 + O2

2) The mass fraction of sodium hydroxide solution after water electrolysis8 (

Solution:1After the complete reaction of mixing and heating, oxygen is generated, and the mass is x2kclo3 = (mno2 + heating) = 2kcl + 3o2 245 96

x245 96

xx Answer: Oxygen is produced after the mixing heating is completely reacted with a mass of.

2.The oxygen mass is produced after the mixed heating reaction

The mass of potassium chlorate in the original mixture is x

2kClO3 = (mNO2 + heated) = 2kCl + 3O2 245 96

x245 96

xx Answer: The mass of potassium chlorate in the original mixture is.

3.From the question, it can be seen that the oxygen quality is.

The mass of potassium chlorate in the original mixture is x

2kClO3 = (mNO2 + heated) = 2kCl + 3O2 245 96

x245 96

xx Mass of manganese dioxide

Answer; The mass of manganese dioxide is.

The relative molecular weight of carbon dioxide is 44 and that of water is 18Therefore, it can be seen that the mass ratio of the two is one to two, one molecule of carbon dioxide corresponds to one carbon atom, and one molecule of water corresponds to two hydrogen. Therefore, it can be seen that the ratio of carbon to hydrogen in the substance is one to four. Therefore, A and D should be chosen

The mass ratio of AC carbon dioxide to water is 22:9

The ratio of the amount of carbon dioxide to the amount of water is 1:1

Then the ratio of carbon to hydrogen is 1:2

So choose AC

Solution: CA + H2O = CA(OH)21 1

ca(oh)2 +co2=caco3 + h2o1 100

xx = 15 grams.

Answer: Molar calcium hydroxide can be obtained by fully reacting calcium oxide with water? Introducing an appropriate amount of carbon dioxide gas into the solution yields 15 grams of precipitate.

Listing the chemical equation, let the relative molecular mass of r be x. Because in the air complete reaction gives 7 grams of roThe added mass is the mass of oxygen, and the corresponding proportional relationship is listed: 2*2x=5*32, and finally x=40, and the answer is b

Hello landlord: From the title, it can be seen that R to Ro only adds O, so N(O)=(5-2) 16=1 8molSo according to the conservation of electrons of gain and loss, so n(r)=1 8mol

And because m(r)=5g, m(r)=40g mol. I hope you will adopt it, thank you.

Let the mass of calcium carbonate be x, and the mass of CaCl2 produced is y

cac03+hcl==cacl2+h2o+co2100...111...44

x...y...

x/100=y/111=

Solution: x=10, y=

Then the quality score is.