Water
| |
| Names | |
|---|---|
| IUPAC name
Water
| |
| Other names
DHMO
Dihydrogen monoxide Dihydrogen oxide Hydrogen oxide Oxidane Hydric acid Hydrogen hydroxide Hydrogenyl alcohol | |
| Properties | |
| H2O | |
| Molar mass | 18.01528(33) g/mol |
| Appearance | Colorless liquid |
| Odor | Odorless |
| Density | See here |
| Melting point | 0 °C (32 °F; 273 K) (ultrapure water can supercool as low as −48.3 °C) |
| Boiling point | 100 °C (212 °F; 373 K) |
| Solubility | Reacts with acid anhydrides, acyl chlorides, certain inorganic chlorides, Miscible with some lower-chain liquids (alcohols, amines, carboxylic acids, cyclic ethers), acetaldehyde, acetone, acetonitrile, DMSO, DMF, hydrazine, hydrogen cyanide, hydrogen peroxide, N-Methyl-2-pyrrolidone, nitric acid, sulfolane, sulfuric acid Slightly soluble in carbonate esters, ethyl acetate, furfural, methyl ethyl ketone, methyl formate, nitromethane Immiscible with carbon disulfide, esters, ethers, halocarbons, hydrocarbons |
| Vapor pressure | 0.031276 atm (at 25 °C) |
| Acidity (pKa) | 13.995 |
| Thermochemistry | |
| Std molar
entropy (S |
69.95 ± 0.03 J·mol-1·K-1 |
| Std enthalpy of
formation (ΔfH |
-285.83 ± 0.040 kJ/mol |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose)
|
~100,000 mg/kg |
| Related compounds | |
| Related compounds
|
Hydrogen peroxide |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Water is a chemical compound with the formula H2O and is a versatile solvent often used in the laboratory.
Contents
Properties
Chemical
Water the most commonly used laboratory solvent, due to its property of not being flammable like many other solvents, ability to dissolve a wide range of compounds, cheapness and availability, and non-toxicity as well as being mostly inert.
Water will react with alkaline metals, alkaline earth metals (except beryllium) and lanthanides to release hydrogen gas.
- M + H2O → MOH + H2
Addition of water to many anhydrous transition metal salts and some post-transition metal salts will give the hydroxy salt of said metal, which, if heated will not return back to the anhydrous salt, but instead it will form a compound containing an oxygen or a hydroxide and the anion of the compound. A good example is the dissolution of tin(II) chloride or aluminium chloride in water. Transition metal halides, like titanium(IV) chloride will hydrolyze in contact with water.
Self-ionization
Water is able to ionize and form hydronium and hydroxide ions in solution in concentrations of about one ten millionth of a molar.
Physical
Water is a clear colorless liquid with a density of 1.00 g/ml at 4 °C, a boiling point of 100 °C, and a freezing point of 0°C. It is odorless, tasteless, and somewhat volatile.
Availability
Distilled water is available at most grocery stores for less than one dollar per gallon. Tap water is essentially free. Some home setups for distillation of water can actually produce enough distilled water for lab use, but energy costs are a major concern.
For most reactions, it's best to used distilled water, either bought or made, as the presence of chlorine in tap water may interfere with some reagents (ex: silver nitrate).
Preparation
Water can be prepared by the ignition of any hydrocarbon or hydrogen. It can also be prepared by distillation of water from a lake or ocean, however none of the methods are economical due to the cheap price of water.
Projects
Water is a widely used solvent and is often the only solvent used in beginner inorganic chemistry, or its more common term of "wet chemistry".
- Dissolving alkali metals in water
- Making hydroxides from metal oxides
- Hydrated crystals
- Ice crystals
- Cooling baths
- Oxoacids
- Generating hydrogen or oxygen via electrolysis
- Solvent extraction/washing
Handling
Safety
Ingestion of large amounts (really, really large amounts) of pure water can upset the osmotic balance is the body. The human body is composed mainly of water, though small amounts of any liquid, including water, can be fatal when inhaled, through a process commonly known as drowning.
It is recommended that a specific supply of distilled water is purchased.
Storage
Distilled water should be stored in closed bottles, away from heat or light sources to limit its evaporation, as well as to reduce its contamination with dust or other contaminants (otherwise you won't be needing pure water).
If you need ultrapure water for various sensitive analyses (such as pH), it's mandatory you air-tight the water bottle/containers, as water will rapidly absorb carbon dioxide from air, which lowers the pH.
Disposal
Down the drain the water goes. Or in the garden. Just be sure it's clean water.
References
Relevant Sciencemadness threads
- Why does my Distilled water have a pH of 5.6 ???
- Distilled water density
- Distilled vs Deionized Water
- Distilling water
- distilled water
- Purity of store bought distilled water
- how to make double distilled water
- Survey : How much distilled water is enough ?
- NFPA-704: water is not reactive at all ?
- Water battery with an electrode of a Magnesium salt.
- Water >> H2 and 1/2O2 electrolysis
- How much of water is empty space?
