A bicarbonate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound. Many bicarbonates are soluble in water at standard temperature and pressure, particularly sodium bicarbonate and magnesium bicarbonate; both of these substances contribute to total dissolved solids, a common parameter for assessing water quality.
Ammonium Hydrogen Carbonate
At room temperature ammonium bicarbonate is a white, crystalline powder with a slight odour of ammonia that can dissolve in water to give a mildly alkaline solution. It is however insoluble in acetone and alcohols. Ammonium bicarbonate decomposes at 36 to 60 °C into ammonia, carbon dioxide and water vapor in an endothermic process (as it is with many ammonium salts) and so causes a drop in the temperature of the water. When reacted with acids carbon dioxide is produced, while reactions with alkalis give ammonia.
Sodium Hydrogen Carbonate
NaHCO3 is a salt which consists of the ions Na+ and the bicarbonate anion, HCO3-. It has a pKa of 6.3 in water which causes aqueous solutions to be mildly alkaline:
HCO3- + H2O H2CO3 + OH-
 Reaction of sodium hydroxide with carbon dioxide
NaHCO3 may be obtained by the reaction of carbon dioxide with an aqueous solution of sodium hydroxide :
The initial reaction produces sodium carbonate:
CO2 + 2NaOH Na2CO3 + H2O
Further addition of carbon dioxide produces sodium bicarbonate, which at sufficiently high concentration will precipitate out of solution:
Na2CO3 + CO2 + H2O 2NaHCO3
Potassium Hydrogen Carbonate
Potassium bicarbonate is soluble in water, and is often found added to bottled water to affect taste; however, it is not soluble in alcohol. Decomposition of the substance occurs between 100°C and 120°C into K2CO3 (potassium carbonate), H2O (water), and CO2 (carbon dioxide). In concentrations greater than 0.5%, KHCO3 can have phytotoxic effects on plants (potassium bicarbonate has widespread use in crops, especially for neutralizing acidic soil), although there is no evidence of human carcinogenicity, no adverse effects of overexposure, and no LD50.