Bicarbonate is the conjugate base of carbonic acid and the conjugate acid of carbonate ion.Bicarbonate (HCOthree-）The atoms of are arranged in a plane structure. The carbon is located in the center and is bonded to three oxygen atoms (one C=O, one C-OH, and one C-O-）。
The following equilibrium exists in the aqueous solution, and bicarbonate can be ionized to form carbonate ion (COthree2-）And hydrogen ion (H+）, will also be hydrolyzed to formHydroxyl ion（OH-）And carbonic acid (HtwoCOthree）, due to the hydrolysis of bicarbonate (producing OH-）Greater than ionization (producing H+）Therefore, its aqueous solution is weakly alkaline.
Chinese name
Bicarbonate
Symbol
HCO3-
Valence
-1 Price
Acid-base property
Bicarbonate is alkaline
Nature
Weak acid radical
Atomic arrangement
Flat structure with carbon at the center
Meaning
The conjugated base of carbonic acid is also the conjugated acid of carbonate ion
CarbonateAnd bicarbonate are both ions, andWeak acid radicalIons, bothEasy to exist in alkaline conditionsNext,CarbonateAcidity is weaker thanBicarbonateTherefore, it is easier to hydrolyze, so the alkalinity of carbonate aqueous solution is stronger than that of bicarbonate aqueous solution.The hydrolysis degree of carbonate ion is large, and bicarbonateMost of the combined salt is soluble salt,andMany salts combined with carbonate ions are insoluble,Bicarbonate can combine with hydroxide to form carbonate and water.Bicarbonate does not react with carbonic acid.Bicarbonate reacts with acetic acid and phosphoric acid, which is medium strong acid.
HCOthree-+ H+⇌ HtwoO + COtwo↑
HCOthree-+ OH-⇌ HtwoO + COthree2-
characteristic
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Solubility of bicarbonate and metal ion products[1]
Bicarbonate ions cannot coexist with hydrogen and oxygen ions in large quantities, emphasizing "large quantities".In fact, these two ions can coexist in a small amount.This involvesIon balanceQuestion.There is a dynamic ion balance in any solutionIonsOfconcentrationThe product of a certain power of is a fixed value, in which the constant is called“Chemical equilibrium constant”。This limits the maximum ionconcentrationIf the limit is exceeded, the ion concentration will be generated by the reactionGasorprecipitateWait and automatically descend backEquilibrium state。
Ion test
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The method for testing carbonate ion or bicarbonate ion is as follows: First, add sufficient dilute hydrochloric acid to the solution, and the generated gas passes through sufficient aciditypotassium permanganateAfter the solution is added, clear lime water will become turbid.Take another solution and add a small amount of CaCltwoOr BaCltwoSolution, if there is no precipitation, only contains bicarbonate ions;If precipitation occurs, dilute nitric acid is added to the filtered filter residue to precipitate COtwoAdd diluted hydrochloric acid to the filtrate, and no CO will be generatedtwo, it only contains carbonate ion;If CO is generatedtwo, it contains both carbonate ion and bicarbonate ion.[1-3]
