The steps of coarse salt purification, expressed in a chemical equation.

Crude table salt contains insoluble and soluble impurities (such as sediment and K+, Mg2+, SO42+, Ca2+ ions, etc.). Insoluble impurities can be removed by dissolution and filtration; Soluble impurities are salts that can react with impurity ions to the solution of crude table salt, so that the precipitate is formed and then filtered to remove. For K+, the solubility of KCl is greater than that of NaCl, and the content is small, and after evaporation and concentration, NaCl is crystal precipitated, and NaCl crystals can be obtained by separation.

ba2++so42-═baso4↓

ca2++co32-═caco3↓

ba2++co32-═baco3↓

mg2++2oh-═mg(oh)2↓

co32-+2h+═co2↑+h2o

From the above principle, it can be seen that the purpose of adding barium chloride is to remove SO42-, and the purpose of adding sodium carbonate solution and sodium hydroxide solution is to remove Ca2+, Mg2+, and excess Ba2+

The filtered precipitate was BaSO4, CaCO3, BaCO3, Mg(OH)2;

Dilute hydrochloric acid was added to the 3 types to neutralize the excess sodium carbonate and sodium hydroxide solution added above.

Junior Chemistry - Crude Salt Purification.

Add BACL2 to produce a white precipitate, stop when the white precipitate no longer increases, consider the precipitate Baso4, and remove the impurity SO42-;

ba2+]+so42-]=baso4

Na2CO3 was added to produce a white precipitate, which was stopped when the white precipitate no longer increased, and the precipitated CaCO3 was considered, and the impurities Ca2+ and excess Ba2+ were removed

co32-]+ca2+]=caco3 [co32-]+ba2+]=baco3

NaOH is added to produce a white precipitate, which stops when the white precipitate no longer increases, and the precipitate Mg(OH)2,;

2oh-]+mg2+]=mg(oh)2

Finally, HCl is added until the solution is neutral.

oh-]+h+]=h2o

Finally, the addition of hydrochloric acid can be excessive, and the excess hydrochloric acid can be removed by using the volatility of hydrochloric acid.

Coarse salt purification:

First, the coarse salt is dissolved in water, then filtered (note that one stick, two low, and three leaning), and then add excess BaCl2 solution to remove Na2SO4: BACL2+Na2SO4==BaSO4 +2NaCl

Then add excess NaOH solution and remove MgCl2: MgCl2+2NaOH ==Mg(OH)2+2NaCl

Then add excess Na2CO3 solution and remove CaCl2 and BaCl2 (two reaction equations): Na2CO3 + CaCl2==CaCO3 +2NaCl Na2CO3 + BaCl2==BaCO3 +2NaCl

Finally, an appropriate amount of hydrochloric acid is added dropwise until it no longer produces gas, and NaOH and Na2CO3 are removed (pH test paper can be used to detect pH level, and there are also two reaction equations): HCl+NaOH==NaCl+H2O

2hcl+na2co3==2nacl+h2o+co2↑

The solution is evaporated and NaCl crystals are precipitated.