Calcium bicarbonate
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| Names | |
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| IUPAC name
Calcium hydrogencarbonate
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| Systematic IUPAC name
Calcium bicarbonate | |
| Other names
Cleansing lime
Bicarbonate of lime Rain salt | |
| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
PubChemCID
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| UNII | |
CompTox Dashboard(EPA)
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| Properties | |
| Ca(HCO3)2 | |
| Molar mass | 162.11464 g/mol |
| 16.1 g/100 mL (0 °C) 16.6 g/100 mL (20 °C) 18.5 g/100 mL (100 °C)[citation needed] | |
| Hazards | |
| Occupational safety and health(OHS/OSH): | |
Main hazards
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Irritant |
| Flash point | Non-flammable |
| Related compounds | |
Othercations
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Magnesium bicarbonate |
Related compounds
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Sodium bicarbonate |
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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Calcium bicarbonate,also calledcalcium hydrogencarbonate,has the chemical formula Ca(HCO3)2.The term does not refer to a known solid compound; it exists only inaqueoussolution containingcalcium(Ca2+),bicarbonate(HCO−
3), andcarbonate(CO2−
3) ions, together with dissolvedcarbon dioxide(CO2). The relative concentrations of these carbon-containing species depend on thepH;bicarbonate predominates within the range 6.36–10.25 in fresh water.
All waters in contact with the atmosphere absorb carbon dioxide, and as these waters come into contact with rocks and sediments they acquire metal ions, most commonly calcium andmagnesium,so most natural waters that come from streams, lakes, and especially wells, can be regarded as dilute solutions of these bicarbonates. Thesehard waterstend to form carbonate scale in pipes and boilers, and they react with soaps to form an undesirable scum.
Attempts to prepare compounds such as solid calcium bicarbonate by evaporating its solution to dryness invariably yield instead the solidcalcium carbonate:[1]
Very few solid bicarbonates other than those of thealkali metals(other thanammonium bicarbonate) are known to exist.[clarification needed]
The above reaction is very important to the formation ofstalactites,stalagmites,columns, and otherspeleothemswithincaves,and for that matter, in the formation of the caves themselves. As water containing carbon dioxide (including extra CO2acquired from soil organisms) passes through limestone or other calcium carbonate-containing minerals, it dissolves part of the calcium carbonate, hence becomes richer in bicarbonate. As the groundwater enters the cave, the excess carbon dioxide is released from the solution of the bicarbonate, causing the much less soluble calcium carbonate to be deposited.
In the reverse process, dissolved carbon dioxide (CO2) in rainwater (H2O) reacts withlimestonecalcium carbonate(CaCO3) to form soluble calcium bicarbonate (Ca(HCO3)2). This soluble compound is then washed away with the rainwater. This form of weathering is calledcarbonationandcarbonatation.
In medicine, calcium bicarbonate is sometimes administered intravenously to immediately correct the cardiac depressor effects ofhyperkalemiaby increasing calcium concentration in serum, and at the same time, correcting the acid usually present.
References
[edit]- ^"Baking Soda".Archived fromthe originalon 2000-09-29.