Each substance in the following table contains a small amount of impurities, and the reagents select

Substance Impurities The reagent (or method) selected to remove impurities

H2 water vapor concentrated sulfuric acid.

H2 CO2 soda lime.

Cu Zn is fully reacted with dilute sulfuric acid and filtered.

Fe ZN ferrous sulfate solution.

Cao CaCO3 pyrolysis.

FeCl3 HCl iron oxide.

Na2SO4 Na2CO3 dilute sulfuric acid.

NaOH Na2CO3 calcium hydroxide solution.

NaCl MgSO4 barium hydroxide solution.

nano3 cuso4 barium hydroxide solution.

NaCl MgCl2, CuCl sodium hydroxide solution.

Na2SO4 NaOH, Na2CO3 dilute sulfuric acid.

Substance Impurities The reagent (or method) selected to remove impurities

H2 water vapor through concentrated sulfuric acid.

H2CO2 passes through sodium hydroxide solution.

Cu Zn reacts with dilute sulfuric acid.

fe zn is attracted with a magnet.

Cao CaCO3 is calcined at high temperature.

FeCl3 HCl plus iron hydroxide.

NaSO4 NA2CO3 plus sulfuric acid.

Naoh Na2CO3 plus lime water.

NaCl MgSO4 plus barium hydroxide.

nano3 cuso4 plus barium hydroxide.

NaCl MgCl2, CuCl plus sodium hydroxide.

Na2SO4 NaOH, Na2CO3 plus sulfuric acid.

1. Concentrated sulfuric acid 2, through Ca(OH)2 3, HCl 4, FeSO4 5, high temperature decomposition.

6. Fe(OH)3 7, H2SO4 titration with NaOH 8, I really didn't expect this PS: It is not right to add Ca(OH)2, and impurities are introduced 9, Ba(OH)2 hydrochloric acid titration.

10. Ba(OH)2 nitrate titration 11, NaOH HCl titration 12, sulfuric acid titration to pH=7

Chemistry in high school, read the books by yourself, and there are books on them.

a、cacl2

Can be used with an overdose. na2co3

Solution reaction generation.

Calcium carbonate precipitation and sodium chloride can remove impurities but introduce a new impurity sodium carbonate, which does not conform to the principle of impurity removal, so the method adopted by the option is wrong B, K2CO3

Can be with sufficient amount. Formed by dilute hydrochloric acid reaction.

Potassium chloride, water and carbon dioxide, re-evaporation and crystallization, can remove impurities without introducing new impurities, in line with the principle of impurity removal, so the method adopted by the option is correct

c. Cuo solid can be formed by reaction with dilute hydrochloric acid.

Copper chloride and water, copper does not react with dilute hydrochloric acid, but will remove the original substance, which does not meet the principle of impurity removal, so the method adopted by the option is wrong

d. The removal of carbon monoxide in carbon dioxide cannot be ignited, because when carbon dioxide (cannot be burned and cannot support combustion) is present in large quantities, a small amount of carbon monoxide will not be burned, so the method adopted by the option is wrong

Therefore, b

Choose AA, yes, MgCl2 + 2NaOH = = Mg(OH)2 + 2NaCl, just filter out the Mg(OH)2 precipitation.

B. No, Na2SO4 + BACl2==BaSO4 +2NaCl, although BASO4 can be filtered out, NaCl will become a new impurity.

C. No, caCO3==high temperature==cao+CO2, limestone (caCO3) is gone, but new impurities are generated cao. Hydrated lime is Ca(OH)2

d. No, by clarifying the lime water Ca(OH)2+CO2==CaCO3 ++H2O, it is CO2 that is removed, but the impurity Co is not removed. It's the opposite.

A is false, mg(OH)2 is not a precipitate, b, yes, baso4 is a precipitate.

C No, there will be new impurities cao

D is wrong, what is removed is CO2, CO2 + CA(OH)2==CAC3 (down arrow) + H2O

The first floor is correct, and the second floor is please, please go home and re-study junior high school chemistry.

agno3 kcl + agno3 = agcl (Shenyou Bureau Yuandian) + kno3

Ca(OH)2 Ca(OH)2+CO2=CaCO3 + H2O

Heat Labi through H2 CuO+H2=Cu+H2O (evaporation).

A. KOH can react with FeCl3 solution to generate iron hydroxide precipitate and potassium chloride, which can remove impurities but introduces a new impurity potassium chloride, which does not meet the principle of impurity removal, so the method taken by the option is wrong

B. Iron powder can react with CuSO4 to form ferrous sulfate and copper, and iron powder reacts with Fe2 (SO4)3 solution to form ferrous sulfate, which can not only remove impurities, but also remove the original substance, which does not meet the principle of removing impurities, so the method adopted by the option is wrong

c. CaCO3 can react with dilute hydrochloric acid to generate calcium chloride, water and carbon dioxide, but it will remove the original substance, which does not conform to the principle of impurity removal, so the method adopted by the option is wrong

D. CO2 can react with NaOH solution, hydrogen can not react with NaOH solution, and then remove water through a washing cylinder containing concentrated sulfuric acid, which can remove impurities and does not introduce new impurities, which is in line with the principle of impurity removal, so the method adopted by the option is correct

Therefore, choose D

KOH reacts with FeCl3 solution to form precipitate and KCL, and introduces new impurities, which does not conform to the principle of impurity removal, so it is wrong;

CuSO4 reacts with Fe to form Cu and FeSO4, and then filters to remove impurities, so it is correct;

CO2 reacts with NaOH, but hydrogen cannot, so it can be removed through a gas washing cylinder containing NaOH solution, and then through a washing gas bottle containing concentrated sulfuric acid, so it is correct;

CaCO3 is insoluble in water, and nano3 can be soluble in water, so it can be dissolved, filtered, and evaporated, which can achieve impurity removal, so it is correct;

CO2 reacts with lime water to react the original substance, which does not conform to the principle of removing impurities, so it is wrong;

FeCl3 reacts with Fe to form FeCl2, and then filters to remove impurities, so it is correct;

Both of them react with dilute nitric acid, which does not conform to the principle of impurity removal, so it is wrong;

BaCO3 reacts with HCl to react the original substance, which does not conform to the principle of impurity removal, so it is wrong, so C is chosen

CaCO3 Powder (Na2CO3): H2O Nano 3 (NaCl): AgNO3 Explanation CaCO3 is insoluble in water and Na2CO3 is soluble in water.

NaCl + (agno3) = (agCl) + nano3 can be generated by dissolving and filtering with water, and the precipitate can be removed.

CaCO3 powder (Na2CO3): Ca(OH)2Na2CO3 + Ca(OH)2====2NaOH + CaCO3 (precipitate).

This problem is not very good, in fact, as long as the mixture is dissolved, and then filtered, the filter residue is insoluble CaCO3

There's no need to add reagents.

CO2 can react with sodium hydroxide solution to generate sodium carbonate and water, CO does not react with sodium hydroxide solution, can remove impurities and does not introduce new impurities, in line with the principle of impurity removal, the chemical equation of the reaction is: CO2 + 2NaOH Na2CO3 + H2O

To remove Na2CO3 in NaOH solution, the essence is to remove carbonate ions, sodium carbonate solution can be used to react with calcium hydroxide to generate calcium carbonate precipitate and sodium hydroxide solution, and then filtered, impurities can be removed and no new impurities are introduced, in line with the principle of impurity removal, the chemical equation of the reaction is: Ca(OH)2 + Na2CO3 = CaCO3 + 2NaOH

To remove KCl in KNO3 solution, the essence is to remove chloride ions, KCL solution can be used to react with silver nitrate solution to generate silver chloride precipitate and potassium nitrate solution, and then filtered, impurities can be removed and no new impurities are introduced, in line with the principle of impurity removal, the chemical equation of the reaction is: KCL + AGNO3 AGCL + KNO3

To remove Na2CO3 in NaCl solution, the essence is to remove carbonate ions, sodium carbonate solution can be used to react with dilute hydrochloric acid to generate sodium chloride, water and carbon dioxide, which can remove impurities and no new impurities are introduced, in line with the principle of impurity removal, the chemical equation of the reaction is: Na2CO3 + 2HCl 2NaCl + H2O + CO2 (reasonable).

Therefore, the answer is: CO2+2NaOH Na2CO3+H2O; ca（oh）2+na2co3=caco3↓+2naoh；kcl+agno3═agcl↓+kno3；Na2CO3+2HCl, 2NaCl+H2O+CO2 (reasonable).

A can be identified by adding KSCN solution, and can not remove impurities, so in addition to ferric chloride in heteroferrous chloride solution, iron powder should be selected, so A is wrong;

b Both of them react with sodium carbonate solution and cannot remove impurities, so saturated sodium bicarbonate solution should be selected, so b is wrong;

c When new impurities sodium ions are introduced, an appropriate amount of KOH solution should be selected to remove impurities, so C is wrong;

d Fe reacts with copper chloride to form ferrous chloride and Cu, then the use of Fe powder can remove impurities, and no new impurities will be introduced, so D is correct;

Therefore, choose D