Calcium bicarbonate is an inorganicAcid salt，chemical formulaIs Ca (HCO ≮) ₂, soluble in water,relative molecular mass162.06, calcium bicarbonate can besodium bicarbonateAnd water solubleCalcium saltThe reaction is obtained.Calcium bicarbonate is relatively stable below 0 ℃;It is easy to decompose at room temperature to obtain calcium carbonate solid.
Chinese synonym: calcium bicarbonate;Calcium bicarbonate
English name: CALCIUM BICARBONATE;
English synonym: CALCIUMHYDROGENCARBONATE;CALCIUM BIS(HYDROGENCARBONATE)；BIS(CARBONIC ACID HYDROGEN)CALCIUM SALT
CAS No.: 3983-19-5[1]
Physical and chemical properties
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chemical formulaCa(HCOthree)2；relative molecular mass162.06，calcium carbonateDissolve in carbonic acid to form calcium bicarbonate.Evaporate calcium bicarbonate solution to obtain calcium carbonate solid.Soluble in water, decomposed by heating;It forms positive salt with alkali.
When calcium carbonate encounterscarbon dioxideWhen mixing with water, chemical erosion will occur to generate soluble calcium bicarbonate, which will be produced over time“dripping water wears through a stone”The equation:
CaCOthree+COtwo+HtwoO==Ca(HCOthree)two
When calcium bicarbonate is dissolved in water, its aqueous solution is also called "hard water".Groundwater is "hard water".The water in rivers, lakes and seas is not "hard water" (hard water refers to calcium ions andMagnesium ionSuch as metal cations, their carbonates are insoluble in water.Test method for hard water: pour soapy water and shake it. If white scale is produced, the original water is hard water).
Small amount of NaOH: Ca (HCOthree)two+NaOH=CaCO3↓+ HtwoO+NaHCOthree
Ion equation: Ca2++ HCOthree-+OH-=CaCOthree↓+ HtwoO[1]
Karst landform
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Karst landform is that calcium bicarbonate in natural watercaveIt is made by re precipitation of calcium carbonate.When more calcium bicarbonate is dissolved in water, it becomesHard water。Three billion years ago, the original atmosphere over the earth was composed of CO, COtwo，Ntwo，CHfourAnd other gases, but no oxygen. There are seaweeds in the ocean, which consume CO in the atmosphere through photosynthesis under sunlighttwo, resulting in CO dissolved in watertwoThe escape is replenished into the atmosphere, and this change causes calcium bicarbonate Ca (HCO) dissolved in waterthree)twoDecomposition of calcium carbonate into calcium carbonate CaCOthree，Ca(HCOthree)two=CaCOthree↓+COtwo↑+HtwoO。Forming limestone on the earth.But calcium carbonate CaCO in limestonethreeSubject to COtwoAnd water erosion to form limestone caves.When the cave is formedAccumulation landformIt is also forming. Because the cracks infiltrate into the groundwater and contain saturated calcium bicarbonate, it will decompose immediately after outcropping at the cave top.Calcium bicarbonate Ca (HCO) in the cavethree)twoIt decomposes under the action of heat.Over the long years, the above changes have been repeated, forming today's amazingCave wonders。[1]
Determination method
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Study on the determination method of calcium bicarbonate content in solution
Calcium bicarbonate can be used as calcium fortifier, emulsification stabilizer, dough conditioner, nutrition supplement, buffer, loosening agent, flour conditioner, nutrition supplement, yeast food, emulsifier, curing agent, antioxidant synergist, and stabilizer.
1. Determination of pure calcium carbonate reference material
(1) Back titration
Determination of carbonate: accurately weigh three parts of 0.0800~0.1000g pure calcium carbonate with analytical balance into three clean conical flasks, dissolve them with 0.1564 mol/L hydrochloric acid, and then boil them for 5min.After cooling, add 2-3 drops of methyl orange indicator, shake up, and use 0.08367mol/Lsodium hydroxideReverse titrate until the solution color changes from yellow to orange, and then record the volume V1 of sodium hydroxide consumed.Carry out the test three times in parallel.
Determination of calcium: weigh three parts of 0.0800~0.1000g pure calcium carbonate in three clean conical flasks, dissolve them with 0.1564mol/L hydrochloric acid, and add 50mL successivelyDeionized water，3mLTriethanolamineAdjust the pH value with sodium hydroxide to more than 12, add 1-2 drops of calcium indicator, shake up, titrate with EDTA of known concentration until the color changes from colorless to light blue, which is the end point, and record the volume V4.
(2) Potentiometric titration
Determination of carbonate: accurately weigh three parts of 0.0800~0.1000g pure calcium carbonate with analytical balance into three clean conical flasks, dissolve them with 0.1564 mol/L hydrochloric acid, and then boil them for 5min.After cooling, put it inA magnetic stirrerUse the adjusted pH acidity meterComposite electrodePut into this solution, open the agitator, and titrate with sodium hydroxide. At the beginning, record the pH value while titrating. When the pH value changes rapidly, titrate one drop. After the pH value changes basically, record the pH value. In this way, record the pH value changes to very small, and then stop dropping. Then record the volume of sodium hydroxide consumed V3.Carry out the test three times in parallel.
Calcium determination: add 50mL of deionized water, 3mL of triethanolamine, adjust with sodium hydroxide to a pH value greater than 12, finally add 1-2 drops of calcium indicator, shake up, titrate with EDTA of known concentration until the color changes from colorless to light blue, which is the end point, and record the volume V4.
The reaction types determined by the determination of are:
(1) 5.0% sodium bicarbonate and 5.0% calcium chloride;
(2) Precipitation and solution reacted with 5.0% sodium bicarbonate and 5.0% calcium chloride with 5.0% sucrose of the same volume as sodium bicarbonate;
(3) 7.5% sodium bicarbonate and 7.5% calcium chloride;
(4) Precipitation and solution reacted with 7.5% sodium bicarbonate and 7.5% calcium chloride with 8.0% sucrose of the same volume as sodium bicarbonate.
1) Determination of precipitation
Use a spoon to take about 0.1g of precipitate from the beaker that reacts with sodium bicarbonate and calcium chloride, dissolve it with 0.1564 mol/L hydrochloric acid, titrate it with sodium hydroxide, and then titrate it with EDTA to measure calcium ion.Carry out the test three times in parallel.
2) Determination of solution
Use a pipette to accurately measure 5.00mL of solution that has not been precipitated after the reaction of sodium bicarbonate and calcium chloride, use 0.08367mol/L sodium hydroxide for back titration, and then use EDTA for titration to measure calcium ion.Carry out the test three times in parallel.[2]
