Common production methods of calcium hydroxide

Common production processes of calcium hydroxide:

Quick lime powder digestion method: After calcining the limestone into calcium hydroxide, it is then digested with water in a ratio of 1: (3~3.5) to produce a calcium hydroxide liquid that is purified and extracted to remove the residue, and then centrifuged and dehydrated. , dried at 150~300℃, and then selected (above 120 mesh) to get the finished calcium hydroxide. Its CaCO3→CaO CO2↑CaO H2O→Ca(OH)2

Lime powder (CaO 100%) 0.840

Important chemical formulas are:

⒈Calcium hydroxide aqueous solution and saturated sodium carbonate solution can produce sodium hydroxide solution:

Ca(OH)2 Na2CO3=2NaOH CaCO3↓, this behavior is suitable for preparing a small amount of sodium hydroxide solution.

⒉Reaction of calcium hydroxide and carbon dioxide

Ca(OH)2 CO2=CaCO3↓H2O (That is also the reaction between calcium hydroxide and carbon dioxide after smearing the wall with lime slurry. The reason why the wall "sweats" is due to the generation of water H2O. The reason why the wall becomes stronger is mainly due to the generation of water H2O. Calcium carbonate CaCO3 is used. In rural areas, in order to quickly harden the wall, charcoal is burned in a newly painted room to generate carbon dioxide CO2 C O2 (a certain amount) = (ignition) CO2. This performance is all about testing CO2 Equation, when gas enters limewater and becomes turbid, it refers to CO2).

⒊Performance of different amounts of calcium hydroxide and sodium bicarbonate

2NaHCO3 Ca(OH)2(少量)=CaCO3↓ 2H2O Na2CO3

NaHCO3 Ca(OH)2(too much)=CaCO3↓ H2O NaOH

⒋Industrial calcined limestone CaCO3==(high temperature)CaO CO2↑(This embodiment is a method of industrial production technology to intelligently obtain a large amount of CO2, which can be used in two ways)

White smoke often appears at the construction site when making lime slurry Ca(OH)2:CaO H2O=Ca(OH)2 (because the solubility of lime powder decreases as the temperature increases, employees are more inclined to make lime slurry in the summer. When the temperature is high, less lime powder dissolves and leaks, and deeper lime slurry can be made, which means that more calorific value is released)

Lime mortar (lime mortar, lime powder i.e. Ca(OH)2 is applied to the wall, and hardens after reacting with CO2

Ca(OH)2 CO2=CaCO3↓ H2O

⒌The chemical equation embodied by ammonium bifluoride and calcium hydroxide: NH4HF2 Ca(OH)2=CaF2 2H2O NH3

6. The chemical equation of light magnesium oxide and calcium hydroxide: MgCl2 Ca(OH)2=CaCl2 Mg(OH)2↓

⒎The chemical equation embodied by ammonium chloride and calcium hydroxide:

2NH4NO3 Ca(OH)2=2NH3↑ 2H2O Ca(NO3)2

(NH4)2SO4 Ca(OH)2=2NH3↑ 2H2O CaSO4 (this whole process should be carried out under heating conditions as much as possible)

CaCO3 SiO2=CaSiO3 CO2↑ (premise is high temperature weather)

⒏Calcium hydroxide has alkaline properties and is a strong base. Since calcium hydroxide is less soluble than sodium hydroxide solution, calcium hydroxide solution is less irritating and less acidic than sodium hydroxide solution. This feature is that calcium hydroxide is widely used. It is used in agriculture to reduce soil acidity and improve soil structure. It is obvious that it is almost impossible to use sodium hydroxide solution in this kind of site. Organic fertilizer agricultural streptomycin must be prepared with lime and sodium thiosulfate solution in a certain proportion. It was named after it was first used in the French city of Bordeaux in 1885. This light blue thick emulsion organic fertilizer for fruit trees and fruits treats pests and diseases through the high copper content in it. In this process, not only the characteristic that calcium hydroxide can react with copper sulfate is used, but also the characteristic that calcium hydroxide is slightly soluble in water is used to make the medicinal solution viscous, which is beneficial to the adhesion of the medicinal solution to plant branches. In addition, calcium hydroxide reacts with carbon dioxide in the air to form a water-insoluble substance, calcium carbonate, which also helps the liquid adhere to the surface of green plants for a period of time without being washed away by rain.

The reaction of calcium hydroxide and carbon dioxide often occurs in chemical laboratories, industrial production and agricultural production, or in nature. Often used. The fact that quick lime powder cement mortar is used to build bricks and plaster walls is well known. What is less known is that this phenomenon occurs in the sugar industry: in the sugar industry, calcium hydroxide is needed to melt the acid in the new sugar syrup, and then enters the sugar industry. The carbon dioxide turns the remaining calcium hydroxide into precipitate and is filtered out, thus reducing the odor of sugar.

⒐If carbon dioxide continues to enter the calcium hydroxide solution, you will find that the solution first becomes turbid and then returns to normal. The fundamental reason is that carbon dioxide will react with calcium carbonate [CaCO3] to form calcium bicarbonate.

CaCO3 CO2 H2O=Ca(HCO3)2, and calcium bicarbonate [Ca(HCO3)2] is soluble, so the aqueous solution will return again. When the temperature rises, the aqueous solution becomes turbid again, because the calcium bicarbonate undergoes a chemical reaction to form a white precipitate, calcium carbonate.

Ca(HCO3)2==CaCO3↓ CO2↑ H2O

⒑ Calcium hydroxide cannot be placed in reagent bottles with glass stoppers, because although silica is chemically stable, it will react with strong bases, such as NaOH, KOH, RbOH, Ba(OH)2, Ca(OH)2 .

If you put calcium hydroxide into a reagent bottle with a glass stopper, it will appear as follows:

Ca(OH)2 SiO2===CaSiO3↓ H2O

Calcium bicarbonate will adhere to the bottle stopper, causing the water bottle to not open, so it is difficult to store it in a reagent bottle with a glass stopper.

⒒Preparation of calcium hydroxide: H2O CaO=Ca(OH)2 (remember here! There is no precipitation symbol)

⒓There are not many things that junior high school students need to master:

Ca(OH)2 CO2=CaCO3↓ H2OCa(OH)2 Na2CO3=2NaOH CaCO3↓

Ca(OH)2 2HCl=CaCl2 2H2O

Ca(OH)2 H2SO4=CaSO4 2H2O

⒔Calcium hydroxide can also react with chlorine to produce bleach

2Ca(OH)2 2Cl2=CaCl2 Ca(ClO)2 2H2O

Among them, Ca(ClO)2 has the function of bleaching liquid.