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Fe + H2SO4 = FeSO4 + H2 solution weight gain.

x solves: x =

Answer: The mass of Fe participating in the reaction is grams, and the solution increases in grams.

fe + h2so4 = feso4 + h2↑

mg + h2so4 = mgso4 + h2↑

The balance is still balanced, indicating that as much H2 is released. Assuming that both are 2 grams of hydrogen, the mass of iron required is 56 grams, and the mass of magnesium required is only 24 grams, then the mass of copper in the magnesium-copper alloy is 56-24 = 32 grams. The mass ratio of magnesium to copper is 24:32=3:4.

C + O2 = CO2 (ignition), CO2 is lost into the air.

2Cu + O2 = 2Cuo (heating), the solid mass after the reaction is still equal to the solid mass before the reaction, indicating that the mass of O element in the Cuo generated by the reaction is equal to the mass of C in the mixture.

The mass ratio of Cu to C in the mixture is the same as that of Cu to O in Cuo. 64:16=4:1。

CH4 + 2O2 = CO2 + 2H2O (ignition), 2H2 + O2 = 2H2O (ignition).

The mass ratio of carbon dioxide and water generated by the full combustion of the mixed gas is 11:18, which indicates that the mass ratio of C element to H element in the mixed gas is (11 12 44):(18 2 18)=3:

2. The mass fraction of hydrogen in the mixture is 2 (3+2) 100%=40%.

The dilute hydrochloric acid contains 10% = chlorine, and the chlorine contained in the NaCl produced after the reaction is grams, and the mass of NaCl in NaCl is 23 = , and the sodium mass fraction in the original mixture is 100% = 50%.

1: Iron reaction, weight gain, due to the excess of iron powder, the weight increase of the solution is the mass of the iron minus hydrogen in the reaction.

2:3:4 Sufficient amount of sulfuric acid, so iron and magnesium must react completely, copper does not react with dilute sulfuric acid, and the balance balance produces the same mass of hydrogen, so the mass ratio of iron and magnesium is 56:24, which is obtained.

3:4:1 When fully combusted, carbon is produced into carbon dioxide, copper is oxidized to copper oxide, and the mass is the same, then the oxygen in copper oxide is equal to the mass of carbon.

4:40% is calculated according to the mass ratio of carbon dioxide to waterC:H=1:8,5:50% The HCl mass in hydrochloric acid is ,, then the NaCl is and Na is after the complete reaction.

The change of the analysis solution: H2SO4+FE===FESO4+H2 is dilute sulfuric acid before the reaction After the reaction, it is ferrous sulfate solution Excess non-reaction iron powder is filtered Hydrogen escapes from the system The mass change is actually M(FeSO4)-M(H2SO4).

The calculated relative molecular mass is m=56-2=54

And the amount of change in mass is grams, then the amount of each substance involved in the reaction should be the hydrogen gas generated, i.e.

【Test Center】Calculation of chemical reactions containing impurities; Simple calculations of solute mass fractions; sodium carbonate, sodium bicarbonate and calcium carbonate; chemical properties of salt; Calculations based on chemical reaction equations

Special Topic] Calculation of solute mass fraction combined with chemical equations

Analysis] (1) Because calcium carbonate and hydrochloric acid will produce carbon dioxide gas after the reaction, the total mass of the substance in the beaker will be reduced, according to the law of conservation of mass, the reduction of the total mass of the substance in the beaker is the mass of carbon dioxide generated, and the mass of carbon dioxide can be obtained by using the mass of carbon dioxide according to the chemical equation;

2) According to the chemical equation of the reaction of calcium carbonate and hydrochloric acid, the mass of carbon dioxide can be used to find the mass of calcium chloride, and then the mass fraction of calcium chloride can be obtained, where the mass of the solution after the reaction = the mass of the solid participating in the reaction + the mass of the liquid - the mass of the precipitate generated - the mass of the gas generated

Answer] Solution: (1) From the image, it can be seen that the mass of carbon dioxide produced by the reaction is:

Let the mass of calcium carbonate in the original mixture be x

caco3+2hcl═cacl2+h2o+co2↑

x y100/44=x/

x=10g(2) Let the mass of CaCl2 produced by the reaction be y

111/44=y/

y = mass of solution after reaction = 10g+

So the mass fraction of CaCl2 after the reaction is:

Answer: (1) The content of calcium carbonate in the original mixture is 10g; (2) The mass fraction of the solute in the solution obtained after the reaction is 15%.

According to the drawing, the difference in mass before and after the reaction is the amount of CO2 generated: CaCO3 + 2HCl = CaCl2 + CO2 + H2O100g 111 44g

1) The content of calcium carbonate in the original mixture = 10 16 * 100% = 2The mass fraction of the solute in the resulting solution after the reaction =

I don't know how to ask.

Carbon dioxide is generated.

caco3+2hcl==cacl2+h2o+co2↑x y

100/x=111/y=44/

x=10gy=

1) The content of calcium carbonate in the original mixture is 10g;

2) The mass fraction of the solute in the solution obtained after the reaction.

caco₃+2hcl==cacl₂+h₂o+co₂↑a b c

The solution is a=10g, b=indicating that there is an excess of hydrochloric acid, and the sample has fully reacted), c=caco content=10 16=

The impurity content d=16-10=6g

The solute is CaCl and its solution mass fraction =

The mass of the solution should be minus 6g of insoluble impurities].

The amount of mass that is reduced is the amount of carbon dioxide that goes out:

Let the calcium carbonate be x g and the calcium chloride be y pcs.

2hci+caco3=cacl2+co2+h2ox g y g

x=y=calcium carbonate is, the mass fraction of calcium chloride:

m CO2 = i.e.

CaCO3+2H+ =H2O+Ca2+ +CO2 gas compliant.

x Calcium carbonate = , m Calcium carbonate = 10 g

The content of calcium carbonate in the original mixture is 10 16=

Calcium chloride is generated, ie.

Mass fraction of solute.

Solution: (1) From the image, it can be seen that the mass of carbon dioxide produced by the reaction is:

Let the mass of calcium carbonate in the original mixture be x

caco3+2hcl═cacl2+h2o+co2↑x y

100/44=x/

x=10g(2) The mass of CaCl2 produced by the reaction is Y111 44=Y

y = mass of solution after reaction = 10g+

So the mass fraction of CaCl2 after the reaction is:

Answer: (1) The content of calcium carbonate in the original mixture is 10g; (2) The mass fraction of the solute in the solution obtained after the reaction is 15%.

Reaction equations.

2HCI + CAC3 = CACl2 + CO2 + H2O There is carbon dioxide generation in it, and as a result, the central link of the solution is reduced, which is the carbon dioxide generated. Describe the calcium carbonate contained in the impurities. for 10g.

You will count the rest yourself: 10 16*100%=.

Let's see that the solute in the solution is calcium chloride now. Then there is the beginning of the impurities, which we have to subtract. 80-6g=74g

The weight of calcium chloride is the rest of your own calculations, I don't have a calculator.

Solution: Zn+H2SO4==ZnSO4+H2 65 218G x65 2=18G X

x=A; Approximately hydrogen is produced.

Let the percentage concentration of dilute sulfuric acid be x 40ml*Zn+H2SO4==ZNSO4+H2

18g65/98=18g/

x= 53%

Answer: The original percentage concentration of dilute sulfuric acid is: 53%.

The quality of the water: Let the mass of zinc sulfate be generated

zn+h2so4==znso4+h2↑

65 16118g y65/161=18g/y

y = mass fraction of 44,6g (

Answer; The percentage concentration of the zinc sulfate solution generated is.

Note: The above equals signs are approximate and are kept to two decimal places.

zn+h2so4=znso4+h2

65 98 161 2x y z65/

x= y= z=

a.Is there liters of hydrogen produced? (In this case, the density of hydrogen is gram cm and the unit of density is wrong).

b.It turns out that the percentage concentration of dilute sulfuric acid is.

c.The percentage concentration of the zinc sulfate solution generated is.

The first question is whether Nitric acid or potassium nitrate is added to the Zen Sakura dress.

1) If nitric acid is added, 50 10% (50 + 5) Song Da = 1 11 100%.

Ruohe stove is potassium nitrate, (50 10% + 5) (50 + 5) = 2 11 100%.

For example, if the mass of calcium carbonate is known to be 10g, find the mass of carbon dioxide.

Solution: Let the mass of carbon dioxide be x.

CaCO3 2HCl, CaCl2 H2O, CO2 100 44 (atomic mass) 10g x (mass of matter) 100 10g 44 x

Get x 4 4g

Answer: The mass of carbon dioxide is 4 4g.

For example, HNO

ho+noo2, you can tell the shed to be leveled by the following method:

1. Let's assume that the coefficients are ab, c, and

d,,then ahno

bho+cno+do

2. According to the law of mass conservation, the type and number of atoms before and after the reaction remain unchanged. and volumes.

For H atoms, a before the reaction and 2b after the reaction, i.e., a=2b for n atoms, a before the reaction, and c after the reaction, i.e., a=c for o atoms, 3a before the reaction, and b+2c+2d after the reaction, i.e., 3a=b+2c+2d

3. Set an integer arbitrarily, such as a=1

4. Solve the system of equations to get a=1, b=

c=1,d=¼

5. Substituting into the equation to get hno

ho+no+¼o

6. Multiply the equation by 4, remove the denominator, and get 4hno2h

o+4no+o

Once you are familiar with it, these steps can be omitted.

1.Use this formula to calculate.

c = 1000 * density * mass fraction molar mass.

The unit of density is .

grams in milliliters. 2.Let the mass of the original solution be m

22%m=（100+m）*14%

m = amount concentration of substance: 22% m 85*

3.Let the original component be x

molna2o2,ymol

Na2O reaction: 2Na2O2

2h2o4naoh

o2x2x1/2

xna2oh2o

2naohy

Y2Y equations: 78x

62y, which is the total mass of Na2O2 and Na2O before the reaction40(2x+2y) (+

32*1/2x)

This is the mass fraction of NaOH after the reaction (minus the mass of the evolved oxygen) to obtain x=, y=, so m(Na2O2)=

The concentrated sulfuric acid. The density is.

Assuming that the mass of the original solution is x grams.

The mass of the original solution obtained by 175 solution is 175 grams, then the density of the original 150ml solution is 175 g 150 ml = original solution.

The amount of concentration of the substance.

It's 1000**

(mol/l)

Sodium peroxide. Reaction formula of sodium oxide reaction with water respectively: 2

na2o2+

2h2o4naoh

o2na2o+

h2o=2naoh

Set the original mixture.

Na2O2 has a mass of x grams, n

The mass of A2O is Y grams. x+y

7(x*40+y

The mass of Na2O2 in the original mixture is grams, and the mass of Na2O is grams.

Note: The formula is sulfuric acid, respectively

Sodium nitrate, sodium peroxide.

Sodium oxide, sodium hydroxide.

molecular weight of oxygen; where 2 is the coefficient of quantitative reaction of the substance in the reaction formula.

200*8%=mol.

Molar sodium hydroxide corresponds to the molar mixture, what is the mixing ratio of copper oxide and magnesium oxide, and the mass of oxygen is 16* grams, so the content of oxygen element is.

fe---h2

56---2(2(x=