A chemistry question, please come and explain why, I know the answer is C

1. After adding barium nitrate, because sulfate and carbonate will produce precipitation, and barium sulfate is insoluble in dilute nitric acid, but barium carbonate is soluble in dilute nitric acid, the precipitation is filtered and dilute nitric acid is added, if the precipitate is completely dissolved, it means that there is no sulfate but only carbonate; If the precipitate is completely solvent-free, it means that there is only sulfate and no carbonate, and if the precipitate is partially dissolved, it means that both acids are present, so that two ions are obtained! Due to the excess of barium nitrate, these two ions can be avoided from affecting the subsequent identification. If a white precipitate is produced after adding silver nitrate, it can only be silver chloride, because other salts of silver are soluble in dilute nitric acid, so it can be determined whether chloride ions exist.

The first addition of barium nitrate is to generate barium salt precipitation, at this time it may be barium carbonate, after filtration, acid can be tested, if dissolved, it means that there is carbonate, and then add excessive silver ions in the original solution, if the white precipitate is generated, so there is excess acid, and the precipitate is insoluble, it is enough to show that the original solution has chloride ions, because silver chloride is insoluble in acid:

1. Barium nitrate is added to test carbonate ions, and if there is, barium carbonate precipitate will be generated.

4. Filtration is to check impurities.

5. Barium carbonate will react with dilute nitric acid to generate carbon dioxide, and the phenomenon is the formation of bubbles.

2. The addition of silver nitrate is to detect chloride ions and generate silver chloride precipitate.

a. Add excess barium nitrate first, precipitate all the sulfate ions and possible carbonate ions, and whether chloride ions are introduced.

It is then filtered and dilute nitric acid is added to the precipitate and, if bubbles are generated, carbonate ions. If the white precipitate is not completely dissolved, there are sulfate ions.

Then add silver nitrate, and if there is a white precipitate, there are chloride ions.

Barium nitrate is added to precipitate sulfate ions and possibly carbonate ions to precipitate the precipitate. Then add dilute nitric acid to check whether there are carbonate ions, and add silver nitrate to check chloride ions.

a.Answer: Because if a reaction cannot be carried out by itself, the artificial promotion of the reaction should be heating, stirring (which is also a way to make the temperature of the reactants higher), etc., so although it is not wrong to say that water dissolves ammonium nitrate to absorb heat, it cannot start the reaction.

b.Answer: Because according to the valency, the nitride valency in ammonium nitrate is +5 and -3 valence, but they all have to become 0-valent nitrogen, so 1mol of nitrate ions needs 5mol electrons to be reduced, and "oxidizing 1mol of zinc and 1mol of ammonium ions" exactly needs 5mol of electrons, so this option is correct.

CD two options, as long as you judge what the reaction product is, by the title, because you know that ammonium nitrate and zinc powder are mixed according to the mass ratio of 8 ratios, so the amount of the converted substance should be calculated as a 1:1 relationship, but this reaction seems to have not been learned? So this equation could be.

Ammonium nitrate + zinc - 2 times water + nitrogen + zinc oxide (ZNO) so the CD option can be excluded altogether.

(1) The role of manganese dioxide in the reaction is catalysis.

The mass of oxygen produced is 20g+

2h2o2= mno2= 2h2o+ o2↑68 32

x68/x=32/

x=(2)3) 100g*3% The result is preserved to one decimal place).

(1) Catalysts.

2) m(o2)=20+

According to 2H2O2=2H2O+O2, m(H2O2)=mass fraction:

3) If the mass of the solution is x, then there is x = the hydrogen peroxide in the prepared 100g hydrogen peroxide disinfectant with a solute mass fraction of 3% is all ** in the hydrogen peroxide solution in (2), and the mass of 3%*100g of H2O2 in the disinfectant solution should be the same as the mass of H2O2 contained in the hydrogen peroxide solution you use.

From the second question, it can be calculated that the mass fraction of the solution is, that is, 100g3% hydrogen peroxide solution is prepared with hydrogen peroxide solution, no matter how diluted, the mass of hydrogen peroxide contained in the solution remains unchanged, therefore, the solution m (the solution here refers to the hydrogen peroxide solution calculated earlier) is required

The solution is m=

Very simply, it can be known that the mass of 2H2O2 is 3G, and the mass fraction of 3G divided by it is calculated to be about.

(1): cuso4

2): naso4

3): The aqueous solution of K2CO3 is alkaline, which will also make the phenolphthalein solution red(4): CaCl2 solution, phenolphthalein solution.

Exactly the complete reaction.

na2co3 + bacl2 = baco3↓ +2naclx

The column equation is solved to x=

1) The mass fraction of sodium chloride in the soda ash sample (

2) Mass fraction of solute in solution after reaction:

The solute is NaCl: (

1) Na2CO3+BaCl2=2NaCl+BaCO3 can be seen from the chemical equation.

n(Na2CO3)=n(BaCO3)=m(Na2CO3)=

m(nacl)=

nacl%=(

2) After the reaction, the carbonate ions in the solution are completely precipitated, and the solute is NaCl, part of which is the impurity originally contained, and the other part is the N(NaCl)=2N(BaCO3)=, that is.

So the common solute NaCl is.

According to the principle of conservation of mass, the mass of the solution can be calculated as 11+50+, so the solute mass fraction is (

Hello landlord, the fastest calculation with the difference method, first of all, by the mass relationship, the mass of CO2 can be calculated, so according to the amount ratio of CaCO3 and CO2 is 1:1, so the quality sought by the first chain can be calculated from the calcium ion for so open CaCl2 for so the mass is, so the mass fraction is for you, thank you.

The ambient temperature of 120 indicates that the water is in a vapor state.

From Moore's correlation, it can be seen that the pressure ratio is related to the number of molecules.

The ratio of the number of molecules before and after the reaction should be considered.

CH4+2O2==CO2+2H20, which is 3 to 3C2H4+3O2==2CO2+2H20, which is 4 to 4

It can be seen that this group is okay with the same number of molecules before and after the reaction.

c2h2+, which is more than 3

c2h6+, is more than 5

This group is also possible, because one is more and one is less, and as long as it is properly combined, the requirements can be met.

In the same analysis, both c and d are non-compliant.