Carbonate vs Bicarbonate
Human body produces carbon dioxide as a by-product of the metabolism. Most of this carbon dioxide is dissolved in blood plasma and present in the form of bicarbonate. Carbonate and bicarbonate system is mainly responsible for maintaining our blood pH value, and they act as a buffer in our blood. When carbon dioxide is dissolved in water, bicarbonate and carbonic acid are formed, and there is equilibrium between these species.
Carbonate is an ion containing a carbon and three oxygens. It has a negative divalent charge. Carbonate ion has a trigonal planar geometry. Its molecular weight is 60 g mol-1. The structure of the carbonate anion is given below.
Although the carbonate structure is drawn as above, with one carbon- oxygen double bond and two carbon- oxygen single bonds, it is not the actual structure. Carbonate ion shows resonance stabilization. Therefore, all the carbon- oxygen bonds have a similar length, and the oxygen atoms have a partial negative charge (hence, all the oxygen atoms are similar.). When carbon dioxide or bicarbonate is dissolved in water, carbonate ions can be formed. Carbonate ion is in equilibrium with bicarbonate ions. Naturally, carbonate ion is combined with another metal ion or another positive ion to make compounds. There are various types of carbonate rocks, such as limestone (calcium carbonate), Dolomite (calcium- magnesium carbonate), potash (potassium carbonate) etc. Carbonate compounds play a crucial role in the carbon cycle. The compounds containing carbon are converted into sedimentary rocks when they are deposited for a long time. When these rocks are weathering or burning, carbon dioxide is released back to the atmosphere. When heating most of the carbonated compounds, they release carbon dioxide easily. Carbonate compounds are ionic, and they are insoluble in water.
Bicarbonate is a monovalent anion having one hydrogen, one carbon and three oxygens. It is formed from deprotonation of carbonic acid. It has trigonal planar geometry around the carbon centre. Bicarbonate ion has a molecular weight of 61 g mol-1, and it has the following structure.
Bicarbonate shows resonance stabilization between the two oxygens, which are not connected to hydrogen. Bicarbonate is alkaline in nature. Bicarbonate is the conjugate acid of the carbonate ion and the conjugate base of the carbonic acid. Positively charged ions can combine with the negatively charged oxygen in the bicarbonate ion and form ionic salts. The most common salt of bicarbonate is sodium bicarbonate, which is commonly known as baking powder. Bicarbonate compounds release carbon dioxide when reacting with acids.
What is the difference between Carbonate and Bicarbonate?
• Carbonate has a negative two charges, but bicarbonate has negative one charge.
• In bicarbonate ion, there is a proton bonded to one of the oxygen atoms.
• In strong basic conditions, there will be more carbonate ions, whereas in weak basic solution bicarbonate ions will be more.
• Compounds with carbonate ions are not soluble in water at the room temperature and atmospheric pressure. However, many bicarbonate salts are soluble in water at room temperature.
• Carbonate compounds are more stable in nature than the bicarbonate compounds.