Potassium hydroxide facts for kids
Quick facts for kids Potassium hydroxide |
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| IUPAC name | Potassium hydroxide |
| Other names |
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| Identifiers | |
| CAS number | |
| PubChem | |
| EC number | 215-181-3 |
| ChEBI | CHEBI:32035 |
| RTECS number | TT2100000 |
| SMILES | [K+].[OH-] |
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InChI
InChI=1/K.H2O/h;1H2/q+1;/p-1
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| Properties | |
| Molecular formula | |
| Molar mass | 0 g mol-1 |
| Appearance | white solid, deliquescent |
| Odor | odorless |
| Density | 2.044 g/cm3 (20 °C) 2.12 g/cm3 (25 °C) |
| Melting point | |
| Boiling point | |
| 85 g/100 mL (−23.2 °C) 97 g/100 mL (0 °C) 121 g/100 mL (25 °C) 138.3 g/100 mL (50 °C) 162.9 g/100 mL (100 °C) |
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| Solubility | soluble in alcohol, glycerol insoluble in ether, liquid ammonia |
| Solubility in methanol | 55 g/100 g (28 °C) |
| Solubility in isopropanol | ~14 g / 100 g (28 °C) |
| Acidity (pKa) | 14.7 |
| −22.0·10−6 cm3/mol | |
| Refractive index (nD) | 1.409 (20 °C) |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−425.8 kJ/mol |
| Standard molar entropy S |
79.32 J/mol·K |
| Specific heat capacity, C | 65.87 J/mol·K |
| Hazards | |
| NFPA 704 |
0
3
1
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| Flash point | nonflammable |
| U.S. Permissible exposure limit (PEL) |
none |
| Related compounds | |
| Other anions | Potassium hydrosulfide Potassium amide |
| Other cations | Lithium hydroxide Sodium hydroxide Rubidium hydroxide Caesium hydroxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Potassium hydroxide is a white, solid inorganic compound made of potassium and hydroxide. People also call it caustic potash or potassium lye. Like sodium hydroxide, it is a very strong base. It can quickly neutralize acids and dissolve in water. When mixed with water, it gives off lots of heat in an exothermic reaction.
Contents
What Makes Potassium Hydroxide Special?
Potassium hydroxide has a special crystal pattern like NaCl salt. It is hygroscopic, which means it pulls moisture right out of the air. It dissolves easily in liquids, including water, methanol, and alcohol. Because it loves water so much, scientists use it as a desiccant to dry out other chemicals.
Making Soft Soaps and Cleaners
When potassium hydroxide reacts with greasy animal fat, it undergoes saponification. This process turns oils into soft soaps and glycerol. These special soaps dissolve easily in water, making them great for liquid body washes. It is also used to make powerful cleaning solutions that help disinfect surfaces.
Powering Batteries and Electronics
This chemical is a key ingredient in portable energy. An aqueous mix acts as an electrolyte inside many alkaline batteries. It carries electric charges very well in nickel-cadmium cells and nickel-metal hydride batteries. Car makers even use it inside hybrid cars like the Toyota Prius. High-purity versions help etch tiny parts on computer chips and solar cells.
Helping Plants and Making Food
Factories react potassium hydroxide with acids to make potassium phosphate, which provides nutrients in fertilizers. In the food world, it is known as E525 and approved by the FDA. Food makers use it to control acidity and help process tasty foods like cocoa and olives.
Studying Fungi and Nature
Scientists use a drop of this liquid to study wild mushrooms. The liquid reacts with certain fungi like gilled mushrooms, boletes, and polypores, causing them to change color. This handy test helps researchers identify different kinds of mushrooms and lichens quickly.
Staying Safe Around Caustic Potash
Potassium hydroxide is very caustic and can cause a bad burn if touched. It reacts with natural skin oils, making it feel slippery before hurting skin tissue. It can be made harmless when it is neutralised with an acid to create a safe salt.
See also
In Spanish: Hidróxido de potasio para niños
