A carbonate is a salt of carbonic acid , ( H 2 CO 3 ), characterized by the presence of the carbonate ion , a polyatomic ion with the formula CO 2− 3 . The word "carbonate" may also refer to a carbonate ester , an organic compound containing the carbonate group O=C(−O−) 2 .
20-471: The term is also used as a verb, to describe carbonation : the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by the addition of carbon dioxide gas under pressure or by dissolving carbonate or bicarbonate salts into the water. In geology and mineralogy , the term "carbonate" can refer both to carbonate minerals and carbonate rock (which
40-446: A trigonal planar arrangement, with D 3h molecular symmetry . It has a molecular mass of 60.01 g/mol and carries a total formal charge of −2. It is the conjugate base of the hydrogencarbonate (bicarbonate) 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
60-426: A calcium-magnesium carbonate CaMg(CO 3 ) 2 ; and siderite , or iron(II) carbonate , FeCO 3 , an important iron ore . Sodium carbonate ("soda" or "natron"), Na 2 CO 3 , and potassium carbonate ("potash"), K 2 CO 3 , have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass . Carbonates are widely used in industry, such as in iron smelting, as
80-468: A hydrogen ion, an example of Le Châtelier's principle . The result is to make the blood more alkaline (raise pH). By the same principle, when the pH is too high, the kidneys excrete bicarbonate ( HCO − 3 ) into urine as urea via the urea cycle (or Krebs–Henseleit ornithine cycle). By removing the bicarbonate, more H is generated from carbonic acid ( H 2 CO 3 ), which comes from CO 2 (g) produced by cellular respiration . Crucially,
100-519: A neutral oxygen atom. This structure is incompatible with the observed symmetry of the ion, which implies that the three bonds are the same length and that the three oxygen atoms are equivalent. As in the case of the isoelectronic nitrate ion, the symmetry can be achieved by a resonance among three structures: This resonance can be summarized by a model with fractional bonds and delocalized charges: Metal carbonates generally decompose on heating, liberating carbon dioxide leaving behind an oxide of
120-440: A raw material for Portland cement and lime manufacture, in the composition of ceramic glazes , and more. New applications of alkali metal carbonates include: thermal energy storage, catalysis and electrolyte both in fuel cell technology as well as in electrosynthesis of H 2 O 2 in aqueous media. The carbonate ion is the simplest oxocarbon anion . It consists of one carbon atom surrounded by three oxygen atoms, in
140-470: A similar buffer operates in the oceans. It is a major factor in climate change and the long-term carbon cycle, due to the large number of marine organisms (especially coral) which are made of calcium carbonate. Increased solubility of carbonate through increased temperatures results in lower production of marine calcite and increased concentration of atmospheric carbon dioxide. This, in turn, increases Earth temperature. The amount of CO 2− 3 available
160-515: Is carbonatation . Carbonation of ammonia is one step in the industrial production of urea :In 2020, worldwide production capacity was approximately 180 million tonnes. As a fertilizer, it is a source of nitrogen for plants. Urea production plants are almost always located adjacent to the site where the ammonia is manufactured. In the subsequent urea conversion: the ammonium carbamate is decomposed into urea, releasing water: Henry's law states that P CO 2 =K B x CO 2 where P CO 2
180-401: Is a weak acid. In organic chemistry a carbonate can also refer to a functional group within a larger molecule that contains a carbon atom bound to three oxygen atoms, one of which is double bonded. These compounds are also known as organocarbonates or carbonate esters, and have the general formula R−O−C(=O)−O−R′ , or RR′CO 3 . Important organocarbonates include dimethyl carbonate ,
200-399: Is made of chiefly carbonate minerals), and both are dominated by the carbonate ion, CO 2− 3 . Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock . The most common are calcite or calcium carbonate , CaCO 3 , the chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons); dolomite ,
220-434: Is on a geological scale and substantial quantities may eventually be redissolved into the sea and released to the atmosphere, increasing CO 2 levels even more. It is generally thought that the presence of carbonates in rock is strong evidence for the presence of liquid water. Recent observations of the planetary nebula NGC 6302 show evidence for carbonates in space, where aqueous alteration similar to that on Earth
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#1732779710146240-433: Is sensitive to pH, temperature, and pressure. Although di- and trivalent carbonates have low solubility, bicarbonate salts are far more soluble. This difference is related to the disparate lattice energies of solids composed of mono- vs dianions, as well as mono- vs dications. In aqueous solution , carbonate, bicarbonate, carbon dioxide, and carbonic acid participate in a dynamic equilibrium . In strongly basic conditions,
260-427: Is the partial pressure of CO 2 gas above the solution. K B is Henry's law constant. K B increases as temperature increases. x CO 2 is the mole fraction of CO 2 gas in the solution. According to Henry's law carbonation increases in a solution as temperature decreases. Since carbonation is the process of giving compounds like carbonic acid (liq) from CO 2 (gas) {i.e. making liquid from gasses} thus
280-443: Is unlikely. Other minerals have been proposed which would fit the observations. Small amounts of carbonate deposits have been found on Mars via spectral imaging and Martian meteorites also contain small amounts. Groundwater may have existed at Gusev and Meridiani Planum . Carbonation Carbonation is the chemical reaction of carbon dioxide to give carbonates , bicarbonates , and carbonic acid . In chemistry ,
300-523: The absence of such catalysts, carbon dioxide cannot be expelled sufficient rate to support metabolic needs. The enzyme harbors a zinc aquo complex , which captures carbon dioxide to give a zinc bicarbonate: In reinforced concrete , the chemical reaction between carbon dioxide In the air and calcium hydroxide and hydrated calcium silicate in the concrete is known as neutralisation . The similar reaction in which calcium hydroxide from cement reacts with carbon dioxide and forms insoluble calcium carbonate
320-427: The carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide , CO 2 (aq) , is the main form, which, with water, H 2 O , is in equilibrium with carbonic acid – the equilibrium lies strongly towards carbon dioxide. Thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself
340-451: The cyclic compounds ethylene carbonate and propylene carbonate , and the phosgene replacement, triphosgene . Three reversible reactions control the pH balance of blood and act as a buffer to stabilise it in the range 7.37–7.43: Exhaled CO 2 (g) depletes CO 2 (aq) , which in turn consumes H 2 CO 3 , causing the equilibrium of the first reaction to try to restore the level of carbonic acid by reacting bicarbonate with
360-448: The insoluble metal carbonates, CaCO 3 is important because, in the form of scale , it accumulates in and impedes flow through pipes. Hard water is rich in this material, giving rise to the need for infrastructural water softening . Acidification of carbonates generally liberates carbon dioxide : Thus, scale can be removed with acid. In solution the equilibrium between carbonate, bicarbonate, carbon dioxide and carbonic acid
380-633: The metal. This process is called calcination , after calx , the Latin name of quicklime or calcium oxide , CaO, which is obtained by roasting limestone in a lime kiln : As illustrated by its affinity for Ca , carbonate is a ligand for many metal cations. Transition metal carbonate and bicarbonate complexes feature metal ions covalently bonded to carbonate in a variety of bonding modes. Lithium , sodium , potassium , rubidium , caesium , and ammonium carbonates are water-soluble salts, but carbonates of 2+ and 3+ ions are often poorly soluble in water. Of
400-437: The term is sometimes used in place of carboxylation , which refers to the formation of carboxylic acids . In inorganic chemistry and geology , carbonation is common. Metal hydroxides (MOH) and metal oxides (M'O) react with CO 2 to give bicarbonates and carbonates : In mammalian physiology, transport of carbon dioxide to the lungs involves a carbonation reaction catalyzed by the enzyme carbonic anhydrase . In
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