Chemistry for junior high school Exam tomorrow Help Thank you

1) H2(2)CO(3)H2CO3(4)Na2CO3(5)CH4(6) There is no nitrogen element in the question, so nitrogen fertilizer cannot be written. If there is nitrogen element NH4HCO3

Fe + 2O2 = ignition = Fe3O4

CaCO3 = High temperature = Cao + CO2

fe+2hcl=fecl2+h2↑

Fe3O4+4CO==High temperature==4CO2+3Fe

quicklime or calcium hydroxide.

1) Industrial wastewater should be discharged after treatment up to standard, domestic sewage should be treated centrally, a large number of trees should be planted along the South-to-North Water Diversion Project, and secondary pollution should be prohibited.

2）cao+h2o=ca(oh)2

2na+2h2o=2naoh+h2↑

2H2O = energized = 2H2 + O2

17. Copper baso4 cuso4

Fe+CuSo4=Feso4+Cu Ba(NO3)2+CuSO4=BaSO4 +Cu(NO3)2 (I guess this chemical equation, because you only have nitric acid in your question, and there is no condition of barium nitrate, but without barium nitrate, it is impossible to generate a precipitate.)

Rigorous and realistic scientific spirit.

19. Solution: Let the mass of calcium chloride in the original mixture be X, the mass of calcium carbonate generated by reaction is Y, and the mass of sodium chloride generated by reaction is Z

cacl2+na2co3=caco3↓+2nacl

x 53g×20% y z

The solution yields x= y=10g z=

The mass fraction of the resulting solution solute after the reaction was (

Answer: The original mixture contains grams of calcium chloride.

The mass fraction of the resulting solution solute after the reaction was (

1) Clean and non-polluting fuel, it is an elemental : H22) used as a reducing agent and an oxide for gaseous fuel: CO

3) Soda contains an acid: H2CO3

4) Soda ash commonly used as a detergent in life: Na2CO35) is under construction in China"West-to-East Gas Transmission"Engineering, the main component of the natural gas to be transported: CH4

6) A commonly used nitrogen fertilizer, it is a salt: NH4HCO3

7b c (if it is colorless, choose c) 8a 9c 10c 11 (there is a problem, the patina is heated and decomposes to form CO2, and it is impossible for the mass of the solid to remain unchanged before and after) 12 No Figure 13b, except for 11, I can tell you the process.

4. No, d a can be replaced with copper sulfate, 1-6, the rest is fine.

7-13 BC A C C A 12 No figure ab

I haven't learned Moore quality in the third year of junior high school.

Solution: Let calcium chloride xg be generated.

caco3+2hcl=cacl2+co2

100 73 111 4410g x

100：10g=111：xg

x = m (mass of solution) = 10g+

Mass fraction of solution = 11 g

A: The mass fraction of this solution is:

Calcium carbonate 100g mol, carbon dioxide 44g mol, calcium chloride 111g mol

Question: Calcium carbonate reacts with hydrochloric acid to produce carbon dioxide, that is, calcium carbonate reacts completely, and there is "just a complete reaction", it can be seen that hydrochloric acid is sufficient and completely reacted, so the solution after the reaction is calcium chloride aqueous solution, and its solute mass fraction = (

First of all, it is deduced what the various substances are:

Bordeaux liquor is a blue gelatinous suspension of copper sulphate and hydrated lime in different proportions, which is used as a fungicide. Since a is a blue solution, then a must be copper sulfate.

d is hydrated lime calcium hydroxide.

The main component of gastric juice is hydrochloric acid.

The reddish-brown solid should be iron oxide.

C can be converted into both CuSO4 and HCl, so it should be H2SO4 and can react with calcium hydroxide, no problem.

b is something that contains iron or oxygen and can react with copper sulfate and sulfuric acid, so it should be iron.

Now that's all there is to g, I'll talk about it later.

1）fe2o3

2) Displacement reaction.

3) H2SO4 + BACL2 —>BaSO4 (precipitation) + HCl4) can be converted from calcium hydroxide and can react with hydrochloric acid, here there are only two and four, one cannot react, and three cannot be changed from calcium hydroxide.

A copper sulfate, B iron element, C sulfuric acid, D calcium hydroxide, E iron oxide, F hydrochloric acid, G except for non-elemental iron, everything else is possible. A detailed process is needed to be answered tomorrow.

(1) The role of manganese dioxide in the reaction is (to accelerate the decomposition of hydrogen peroxide), and the mass of oxygen generated after the reaction is () g.

MNO2 is a catalyst that accelerates the splitting of hydrogen peroxide.

The decreasing mass is the mass that generates O2 and is 69+

2) Find the mass fraction of the hydrogen peroxide solute? (Please write the process) [6%] Let the mass of the hydrogen peroxide solute be x.

2h2o2=mno2=2h2o+o2↑

x68/x=32/

x = mass fraction of hydrogen peroxide solute is.

1.Catalysis, 69g+

2.Let the mass of the hydrogen peroxide solute be x

2h2o2=mno2=2h2o+o2↑

x68/x=32/

x = so the mass fraction of the hydrogen peroxide solute =

1. Catalysis, the mass of oxygen generated: 69g+

Let the solute mass of the hydrogen peroxide be x

2h202 =mno2=2h2o+o2

x68/x=32/ x=

The solute mass fraction in hydrogen peroxide is:

(1) Manganese dioxide do: catalyst; The mass of oxygen produced after the reaction is: 69+2—; （2）

Manganese dioxide catalyst gives a mass fraction.

The answer is b, your standard answer is wrong.

In this device, when the water stop clamp is opened, the solid reacts with the liquid to produce H2. When the water stop clamp is closed, the resulting H2 pushes the liquid out, separating the solid from the liquid and stopping the reaction.

Therefore, it can be used at any time and stopped at any time. Hope!

The answer is wrong, it is to choose D, only D can realize solid-liquid separation and stop the reaction!

It's late. The answer has already been seen.

Well, when you don't need the H2 gas, close the valve, but the internal reaction continues, and when the air pressure inside is too high, it pushes the liquid into the separating funnel, which separates the liquid from the solid.

But in fact. This device can't do that. Not rigorous. Well, so be it. If you may have a question, ask your teacher.

The other thing is that I personally think that d is fine.

Looks like you're choosing B? And I guess if you look at the following words, I'm afraid that H2 is not soluble in water, but if B is installed, it may cause H2 to escape.

After a long time, there is no effect of shutting down and stopping.

I chose D because when the gas is not needed, the gas in D will force the liquid of the reaction into the long-neck funnel, thus preventing the reaction from proceeding.

Open and use, close and stop There must be a separating funnel to exclude a, b c, d ** is not clear I don't know.

b, After the piston is closed, hydrogen can be pushed out of the spherical tube to stop the reaction.

d. After turning off the switch, the hydrogen will put the acid in the hydraulic return pipe to make the acid and the metal out of contact.

I think that when the water stop clamp is closed in option D, the pressure in the test tube increases, the liquid is pressed back into the long neck funnel, the solid-liquid is separated, and the reaction stops. The principle is that when the gas is too much and the pressure in the device is too large, the liquid will be pressed back into the container, so that the solid and liquid can be separated in time, and the reaction will be stopped.

d,,The simple device of the Qipu generator, the liquid will naturally flow down and react with the solid when the iron clamp is opened (this reaction is a solid + liquid reaction), and the gas generated when the iron clamp is closed will press the liquid in the test tube into the separating funnel, and the reaction can be stopped even if it is stopped. So the D device can be realized.

Because the lit matches burn more vigorously in oxygen and extinguish in carbon dioxide, the remaining two bottles are ignited as gas. Because hydrogen and methane combustion produce water, it is not appropriate for you to choose C, which is used to test the presence of water. D should be chosen, because hydrogen combustion does not produce carbon dioxide, methane combustion produces carbon dioxide, and d is used to test that carbon dioxide is generated.

c Hydrogen and methane cannot be distinguished because both burn and both produce water, which cannot be distinguished from a cold, dry beaker.

Methane combustion produces carbon dioxide, which clarifies lime water and becomes turbid, but hydrogen combustion only produces water, so d can distinguish hydrogen from methane.

Both hydrogen and methane are formed by water after combustion, and the drying beaker is used to detect whether water is formed, so it is impossible to tell, and clarified lime water can detect CO2, so it is feasible.

Matches burn vigorously in oxygen and extinguish in carbon dioxide, hydrogen ignition produces only water, and methane combustion produces carbon dioxide and water, so it is methane that becomes cloudy in clarified lime water, and the remaining one is hydrogen.

c. How do you distinguish between hydrogen and methane? Both are lighter than air and both are flammable, the difference lies in the product, the former is only water and the latter is water plus carbon dioxide, dry cold beaker can only detect the formation of water, there is no way to identify carbon dioxide, so C is unable to distinguish between hydrogen and methane.