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The bicarbonate ion (hydrogencarbonate ion) is an anion with the empirical formula HCO − 3 and a molecular mass of 61.01 daltons; it consists of one central carbon atom surrounded by three oxygen atoms in a trigonal planar arrangement, with a hydrogen atom attached to one of the oxygens.
On the other hand, if a chemical is a weak acid its conjugate base will not necessarily be strong. Consider that ethanoate, the conjugate base of ethanoic acid, has a base splitting constant (Kb) of about 5.6 × 10 −10, making it a weak base. In order for a species to have a strong conjugate base it has to be a very weak acid, like water.
It is the conjugate base of the hydrogencarbonate (bicarbonate) [8] ion, HCO − 3, which is the conjugate base of H 2 CO 3, carbonic acid. The Lewis structure of the carbonate ion has two (long) single bonds to negative oxygen atoms, and one short double bond to a neutral oxygen atom.
The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of carbonic acid (H 2 CO 3), bicarbonate ion (HCO − 3), and carbon dioxide (CO 2) in order to maintain pH in the blood and duodenum, among other tissues, to support proper metabolic function. [1]
In chemistry, the term "carbonic acid" strictly refers to the chemical compound with the formula H 2 CO 3. Some biochemistry literature effaces the distinction between carbonic acid and carbon dioxide dissolved in extracellular fluid. In physiology, carbon dioxide excreted by the lungs may be called volatile acid or respiratory acid.
The HCO 3-is a conjugate base that neutralizes acids, and the H + is a conjugate acid that neutralizes bases by Acid-base homeostasis. The HCO 3-and H + are ideal for buffering pH in the blood and tissues because the pKa is close to the physiological pH = 7.2 – 7.6.
In this equation, the base (B) and the extremely strong base (the conjugate base OH −) compete for the proton. [6] As a result, bases that react with water have relatively small equilibrium constant values. [6] The base is weaker when it has a lower equilibrium constant value. [3]
An acid may also form hydrogen bonds to its conjugate base. This process, known as homoconjugation, has the effect of enhancing the acidity of acids, lowering their effective pK a values, by stabilizing the conjugate base. Homoconjugation enhances the proton-donating power of toluenesulfonic acid in acetonitrile solution by a factor of nearly 800.