Calcium hydrogencarbonate

Magnesium and calcium hydrogencarbonates are known in solution and are responsible for temporary hardness in water. 

A carboxylate derivative of a fully aromatic, water-soluble, hyperbranched polyphenylene is considered as a unimolecular micelle due to its ability to complex and solubilize non-polar guest molecules [23]. The carboxylic acid derivative of hyperbranched polyphenylene polymer (HBP) (My,=5750-7077, Mn=3810-3910) consists of 40-60 phenyl units that branch outward from a central point forming a roughly spherical molecule with carboxylates on the outer surface. The free acid form of HBP was suspended in distilled water and dissolved by adding a minimum quantity of NaOH. The solution was adjusted to pH 6.2 with aqueous HCl. Calcium carbonate crystals were growth from supersaturated calcium hydrogencarbonate solution at room temperature. HBP gave... 

If water contains dissolved calcium hydrogencarbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes ... 

Temporary hardness is easily removed from water by boiling. When heated, the calcium hydrogencarbonate decomposes, producing insoluble calcium carbonate. 

If carbon dioxide is bubbled for a further length of time then the white precipitate of calcium carbonate dissolves and a solution of calcium hydrogencarbonate is produced ... 

If carbon dioxide is bubbled through this solution continuously then it will eventually become clear. This is because of the formation of soluble calcium hydrogencarbonate solution. 

Hardness in water is caused by the presence of dissolved calcium and magnesium compounds, such as calcium hydrogencarbonate or magnesium sulfate. The hardness of the water can be gauged by its ability to form a thick lather with soap. Water that lathers easily is called soft, whereas water that produces very little lather and a scum, is termed hard. Soap (see page 175) is sodium stearate and scum forms as a result of the precipitation of an insoluble stearate ... 

Hard water is produced when rainwater, which is weakly acidic because of the presence of dissolved carbon dioxide, falls upon limestone or chalk which are both forms of calcium carbonate. The acidic solution dissolves calcium carbonate producing a solution of calcium hydrogencarbonate, or hard water ... 

This type of hard water is called temporary hard water, because it can be removed by boiling. Permanently hard water contains calcium and/or magnesium salts which are not decomposed when the water is boiled. Calcium hydrogencarbonate solution decomposes on boiling to calcium carbonate (scale), which can block pipes or fur kettles in hard water districts ... 

Stalagtites and stalagmites are also found in hard water districts. When drops of calcium hydrogencarbonate solution collect on the roof of a cave, the solution decomposes, some of the water evaporates, carbon dioxide is lost and a tiny precipitate of calcium carbonate is left behind. Over many years these specks of calcium carbonate accumulate to form a stalactite. Solution that drips on to the floor undergoes the same decomposition, forming a stalagmite (Rg. 12.1). 

CaCOj + H2O + CO2 Ca(HC03)2 Calcium hydrogencarbonate is a cause of temporary hard water. The soUd is unknown at room temperature. See hardness. 

It is the cause of temporary hardness of water, because the calcium ions react with soap to give scum. Calcium hydrogencarbonate is unstable when heated and decomposes to give solid calcium carbonate. This explains why temporary hardness is removed by boiling and the formation of scale in kettles and boilers. 

If the carbon dioxide continues to be bubbled through, the calcium carbonate eventually redissolves to form a clear solution of calcium hydrogencarbonate ... 

In analogy to experiments performed by Hacke [24,25], we investigated the crystallization of CaCOs under a mono-layer of stearic acid. Eor a more detailed presentation of these results see [7]. If stearic acid is quickly spread onto an aqueous subphase of calcium hydrogencarbon-ate, thin films of CaCOs emerge in direct proximity to the Langmuir film. In the aqueous subphase the following equilibrium reaction occurs ... 

Write equations, including state symbols, for the following reactions a sulfuric add and copper(ii) carbonate b hydrobromic add and calcium hydrogencarbonate c phosphoric(v) add and sodium carbonate d ethanoic add and calcium... 

Figure 8.7 Stalactites and stalagmites are formed as a result of water passing through rocks containing calcium carbonate. The solution running through these rocks contains water, dissolved carbon dioxide and calcium hydrogencarbonate ...

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