Lime digestion method: after calcination of limestone into calcium oxide, it is digested with water at a ratio of 1: (3 to 3.5), and the calcium hydroxide solution is purified and separated, and then dehydrated by centrifugation at 150~. Drying at 300 ° C, and screening (120 mesh or more) is the finished calcium hydroxide. Its CaCO3→CaO+CO2↑CaO+H2O→Ca(OH)2[1]
Japanese lime digestion
Quicklime (CaO 100%) 0.840
The main chemical equations are:
1. The reaction of calcium hydroxide solution and saturated sodium carbonate solution can produce sodium hydroxide:
Ca(OH)2 + Na2CO3 = 2NaOH + CaCO3 ↓, this reaction can be used to prepare a small amount of caustic soda.
2. Reaction of calcium hydroxide and carbon dioxide
Ca(OH)2+CO2=CaCO3↓+H2O (this is the reaction between calcium hydroxide and carbon dioxide after the lime slurry is applied to the wall. The wall will “sweating†because the water H2O is formed and the wall becomes firm because Calcium carbonate CaCO3 is formed. In the countryside, in order to make the wall harder, carbon is burned in the newly-brushed house to produce carbon dioxide CO2 (C+O2=(ignition) CO2). This reaction is also an equation for testing CO2, gas. The turbidity of the lime water is CO2).
3. Reaction of different amounts of calcium hydroxide and sodium bicarbonate
2NaHCO3+Ca(OH)2(small amount)=CaCO3↓+2H2O+Na2CO3
NaHCO3+Ca(OH)2 (excess) = CaCO3↓+H2O+NaOH
4. Industrial calcination of limestone CaCO3 == (high temperature) CaO + CO2 ↑ (this reaction is also a method for industrially preparing a large amount of CO2, used in two ways)
The white smoke on the construction site is in the lime slurry Ca(OH)2:CaO+H2O=Ca(OH)2 (because the solubility of slaked lime decreases with increasing temperature, so workers are more willing to make lime slurry in summer, so the temperature When there is less slaked lime in the high water, more lime slurry can be produced, and this reaction releases a lot of heat)
Lime slurry (lime slurry, slaked lime, ie Ca(OH)2, is applied to the wall and hardens after reacting with CO2
Ca(OH)2+CO2=CaCO3↓+H2O
5. The chemical equation for the reaction of hydrogen fluoride with calcium hydroxide: NH4HF2 + Ca(OH)2 = CaF2 + 2H2O + NH3
6. The chemical equation for the reverse reaction of magnesium chloride and calcium hydroxide: MgCl2+Ca(OH)2=CaCl2+Mg(OH)2↓
7. The chemical equation for the reaction of ammonium nitrate with calcium hydroxide:
2NH4NO3+Ca(OH)2=2NH3↑+2H2O+Ca(NO3)2
(NH4)2SO4+Ca(OH)2=2NH3↑+2H2O+CaSO4 (this process is best carried out under heating)
CaCO3+SiO2=CaSiO3+CO2↑ (condition is high temperature)
8. Calcium hydroxide has the basicity of alkali and is a strong base. Since the solubility of calcium hydroxide is much smaller than that of sodium hydroxide, the calcium hydroxide solution is less corrosive and alkaline than sodium hydroxide. These properties determine the wide range of applications of calcium hydroxide. It is used in agriculture to reduce soil acidity and improve soil structure. It is obvious that it is impossible to use sodium hydroxide in this case. The pesticide Bordeaux mixture is prepared by using a certain ratio of lime milk and copper sulfate aqueous solution. Named after the first use of Bordeaux in France in 1885. This kind of sky-blue viscous suspension pesticide for fruit trees and vegetables is used to eliminate pests and diseases through the copper elements. The utility model not only utilizes the property that calcium hydroxide can react with copper sulfate, but also utilizes the characteristic that calcium hydroxide is slightly soluble in water to make the liquid viscous, which is beneficial to the adhesion of the liquid to the foliage of the plant. In addition, calcium hydroxide reacts with carbon dioxide in the air to form calcium carbonate which is poorly soluble in water. It also helps the liquid to adhere to the surface of the plant for a period of time without being washed away by rain.
The reaction of calcium hydroxide and carbon dioxide occurs frequently in chemical laboratories, in industrial and agricultural production, or in nature. Often used. The fact that lime mortar is smeared with brick walls is well known. It is little known that this reaction occurs in the sugar industry: calcium hydroxide is used to neutralize the acid in the syrup during the sugar process, and then carbon dioxide is introduced. The remaining calcium hydroxide becomes a precipitate and is filtered out to reduce the sourness of the sugar.
9. If carbon dioxide is continuously introduced into the calcium hydroxide solution, the solution will be turbid and clarified first because carbon dioxide will continue to react with calcium carbonate [CaCO3] to form calcium bicarbonate.
CaCO3+CO2+H2O=Ca(HCO3)2, while calcium bicarbonate [Ca(HCO3)2] is readily soluble, so the solution will clarify again. The heated solution becomes cloudy again because the calcium bicarbonate is thermally decomposed to form a white precipitate of calcium carbonate.
Ca(HCO3)2==CaCO3↓+CO2↑+H2O
10. Calcium hydroxide cannot be placed in a reagent bottle with a glass stopper because although the silica is chemically stable, it reacts with a strong base such as NaOH, KOH, RbOH, Ba(OH)2, Ca(OH)2. .
If calcium hydroxide is placed in a reagent bottle with a glass stopper, the following reaction occurs:
Ca(OH)2+SiO2===CaSiO3↓+H2O
Calcium silicate will precipitate on the stopper, causing the bottle to not open, so it cannot be placed in a reagent bottle with a glass stopper.
11. Preparation of calcium hydroxide: H2O + CaO = Ca (OH) 2 (remember here! no precipitation symbol)
12. There are not many things to master in junior high school:
Ca(OH)2+CO2=CaCO3↓+H2O
Ca(OH)2 + Na2CO3=2NaOH+CaCO3↓
Ca(OH)2+2HCl=CaCl2+2H2O
Ca(OH)2+H2SO4=CaSO4+2H2O
Calcium hydroxide
13. Calcium hydroxide can also react with chlorine to form bleach
2Ca(OH)2+2Cl2=CaCl2+Ca(ClO)2+2H2O
Among them, Ca(ClO)2 has a bleaching effect, which is what Gaoyi learned.
Real Estate Architectural Model
Real Estate Architectural Model,Construction Scale Models,Builder Miniature City Models,Real Estate House Scale Model
Nanjing Great Century Art Model Co., Ltd. , , https://www.dsjysmx.com