On the question of chemical impurity removal 20

: Fe does not react with NaOH, so 2Al +2NaOH + 2H2O = 2Naalo2 + 3H2

SiO2 is insoluble in HCl, so 6HCl+Al2O3=2AlCl3+3H2O

Fe2O3 does not react with NaOH, SiO2 can, so SiO2+2NaOH = Na2SiO3+H2O

Fe2O3 does not react with NaOH, Al2O3 can, so Al2O3+2NaOH = 2Naalo2+H2O

When the gas is passed into saturated NaHCO3, CO2 is not dissolved, while SO2 and dissolved in water, SO2 + H2O = H2SO3

N2 is insoluble in water, Cl2+H2O=HCl+HCl

No is insoluble in water, 3NO2 + H2O = 2HNO3 + NO

1。Add NaOH solution, and filter after the aluminum reaction is removed. 2al+2naoh+2h2o=2naalo2+3h2|

2.SiO2 can only react with one acid, HF, add excess dilute hydrochloric acid, and filter it. al2o3+6hcl=2alcl3+3h2o

3.SiO2 can correspond to NaOH, while Fe2O3 cannot. sio2+2naoh=na2sio3+h2o

4. al2o3+2naoh=2naalo2+h2o5. so2+nahco3=nahso3+co2|6.

cl2+2naoh=naclo+nacl+h2o7. no2+2naoh=nano2+nano3+h2o

To put it simply, the method of removing impurities is "the main does not decrease, and the impurities do not increase", and the method of removing impurities is simple, easy to operate, and easy to separate.

To explain simply, the principle of material removal is:

No increase, that is, no new impurities can be introduced while removing impurities;

No reduction, that is, the substance to be purified cannot be reduced;

Simple, i.e., the separation operation is simple and easy;

Easy to obtain, that is, impurity removal reagents are cheap and easy to obtain;

The impurities are converted into the target product, i.e. the method chosen ensures that the impurities are removed, and it is desirable to increase the amount of the substance to be purified.

There are two types of common methods for removing impurities from substances, that is, using the physical properties and chemical properties of substances to remove impurities by physical or chemical methods

1. Take advantage of the differences in physical properties.

1.Solubility difference method: when there is a significant difference in solubility between the purified substance and the impurity, the solubility difference can be used, and then the impurities can be filtered out.

2.Crystallization method: If the solubility of each component in a mixture in a solvent changes with temperature, the crystallization method can be used to remove impurities.

3.Extraction and separating method: using the different solubility of solutes in immiscible solvents, one solvent is used to extract the solute from the solution composed of another solvent, and then the separating funnel is used to separate it.

4.Sublimation method: Separate solid substances that can be sublimated from solid substances that cannot be volatile.

5.Magnet method: The magnet can attract iron, and the iron can be separated from other impurities that cannot be attracted to iron or removed from the substances that cannot be attracted to iron.

6.Dialysis: Dialysis is the operation of separating ions or molecules from the colloidal solution by putting a colloid mixed with ionic or molecular impurities into a semi-permeable membrane bag and putting the bag into a solvent to separate ions or molecules from the colloidal solution. Dialysis is mainly used to purify and refine liquid sols.

7.Distillation: The boiling point of substances is different to separate miscible mixtures.

Second, take advantage of the difference in chemical properties.

1.Thermal decomposition method: For solid mixtures with large differences in stability, thermal decomposition method can be used. For example, the impurities in sodium bicarbonate can be decomposed by heating by heating sodium bicarbonate to obtain sodium carbonate.

2.Redox method: using the oxidation and reduction properties of substances to oxidize or reduce impurities into substances that are easy to separate.

3.Complexation: A complexing agent is added to convert impurities into soluble complexes, making them easily separated from the desired substances.

4.Precipitation method: The impurities in the liquid or gas mixture are converted into precipitate with chemical reagents to remove.

5.Acid-base dissolution method: using the properties of solid impurities to react with acids or alkalis, impurities are converted into soluble salts and removed.

6.Acid and alkali scrubbing method: using the properties of the reaction between impurities and acids or alkalis, the impurities in the gas mixture are transferred to acid solution or alkali solution respectively.

1 n2 o2 scorching copper wire mesh converts gas with solids.

2 CO2 H2ScuSo4 solution Wash gas.

3 Co CO2Naoh solution wash gas.

4 CO2 Co Glowing Cuo Converts Gas with Solids.

5 CO2 HCI saturated NaHCO3 wash.

6 H2s HCI saturated NaHS wash gas.

7 SO2 HCI saturated NaHSO3 scrubbing.

8 C2 HCI saturated saturated saline gas.

9 CO2 SO2 saturated NaHCO3 scrubbing.

10 charcoal powder mno2 concentrated hydrochloric acid (need to be heated) filter.

11 mNO2 C --- heat and burn.

12 Carbon powder cuo dilute acid (e.g. dilute hydrochloric acid) filtering.

13 AI2O3Fe2O3 NaOH (excess), CO2 filtered.

14 Fe2O3Ai2O3 NaOH solution filtered.

15 AI2O3SiO2 hydrochloric acid ammonia filtered.

16 SiO2Zno HCI solution filtered, 17 BaSO4BAC3 HCI or dilute H2SO4 filtered.

18 NaHCO3 solution Na2CO3 CO2 plus acid conversion method.

19 Naci solution NaHCO3 HCI plus acid conversion method.

20 Feci3 solution Feci2 Ci2 plus oxidant conversion method.

21 Feci3 solution Cuci2 Fe, Ci2 filtering.

22 Feci2 solution Feci3 Fe plus reducing agent conversion method.

23 cuo Fe (magnet) adsorption.

Fe(OH)3 colloidal Feci3 distilled water.

Dialysis. 25 cusfes dilute hydrochloric acid filtration.

26 I2 Crystal NACI - Heating Sublimation.

27 Naci crystal NH4Cl -- pyrolysis.

28 kno3 crystals Naci distilled water recrystallization.

1. In fact, to remove impurities is to leave what you want in a mixture and remove what you don't want. It is necessary to find a way to make a thing react with impurities and not with the target substance. For example:

If you want to remove iron powder from copper powder, the target substance is pure copper powder, and the impurities are iron powder. So what can react with iron powder and not with copper powder?

You will analyze that it can be hydrochloric acid!

Because copper is a post-hydrogen metal, it does not react with acids.

But it can react with iron. Then the iron becomes ferrous chloride and dissolves in solution, and the copper powder is still insoluble, so it is separated by filtration.

I think you can develop your interest in chemistry by doing this, and you won't have to worry about memorizing those methods.

Can be deduced for yourself.

In fact, there is an easier way to remove impurities.

It's just with magnets!

Just suck the iron powder out, and that's fine.

Therefore, I think you should analyze each question in detail, and ask the teacher if you don't understand. Instead of memorizing methods and types, anyway, the methods are varied.

It's OK to do more questions in this way

In addition to the impurities in the substance, the specific problems should be discussed in detail, but the general routine and basic standards will not change.

To remove impurities, you can use washing gas, filtration, dispensing, distillation, etc. However, some chemical reagents will be used in some impurity removal processes, so it is necessary to pay attention to the fact that the chemicals used cannot react with the substances to be obtained to avoid bringing in new impurities.

In addition to impurities, you either get out the impurities, or you can get out the substances you want to get, and the specific methods are the methods I mentioned above.