Difference between revisions of "Potassium bicarbonate"

Revision as of 22:17, 16 July 2018

Potassium bicarbonate

Potassium bicarbonate, slightly wet, on a watch glass.
Names
IUPAC name Potassium hydrogen carbonate
Other names Potassium acid carbonate
Properties
Chemical formula	KHCO3
Molar mass	100.115 g/mol
Appearance	White hygroscopic salt
Odor	Odorless
Density	2.17 g/cm3
Melting point	292 °C (558 °F; 565 K) (decomposes)
Boiling point	Decomposes
Solubility in water	33.7 g/100 mL (20 °C) 60 g/100 mL (60 °C)
Solubility	Reacts with acids Insoluble in alcohols, benzene, chloroform, toluene
Vapor pressure	~0 mmHg
Acidity (pKa)	10.329
Thermochemistry
Std enthalpy of formation (ΔfHo298)	-963.2 kJ/mol
Hazards
Safety data sheet	AcrosOrganics
Flash point	Non-Flammable
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	> 2000 mg/kg (rat, oral)
Related compounds
Related compounds	Potassium carbonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium bicarbonate or potassium hydrogen carbonate is a hygroscopic colorless salt of potassium with the formula KHCO₃.It is used as a food additive in the European Union, E 501. It can be found in nature as the rare mineral kalicinite.

Properties

Chemical

Potassium bicarbonate decomposes to potassium carbonate if heated above 290 °C, despite some sources claiming the decomposition occurring at 100 or 120 degrees C.

2 KHCO₃ → K₂CO₃ + CO₂ + H₂O

Potassium bicarbonate, like its sodium counterpart will react with acids to form potassium salt of the said acid.

KHCO₃ + HCl → KCl + H₂O + CO₂

Physical

Potassium bicarbonate is a white hygroscopic solid, soluble in water but insoluble in alcohols.

Availability

Potassium bicarbonate is sold by winemaking stores as a pH regulator/buffer. It is more expensive than sodium bicarbonate.

Some low-sodium baking powders may contain potassium bicarbonate, though most have calcium or magnesium carbonate, so always read the label.

Preparation

Potassium bicarbonate can be made by bubbling carbon dioxide into a solution containing potassium carbonate.

If you have a mixture of potassium and sodium hydroxide, you can dissolve it in alcohol and then bubble excess carbon dioxide in the solution. As potassium bicarbonate is insoluble in alcohol, it will precipitate, while sodium bicarbonate will stay in solution.

Projects

• Make potassium salts
• Buffering agent
• Fungicide

Handling

Safety

Potassium bicarbonate is considered safe and doesn't require special handling.

Storage

In closed bottles. Since it's hygroscopic, it's best to keep it in a desiccator.

Disposal

No special disposal is required. Discard it as you wish.

References

Relevant Sciencemadness threads

• Ancient Potash Making.