Water ion product (Kw) is a concentration product of hydrogen and hydroxide ions. For the reaction:
the equilibrium expression would be:
Note that all pure liquid terms are omitted, hence H2O does not appear in the denominator. At 25 °C, Kw = 1.0×10-14 mol2dm-6 = (Ka)(Kb)
Aqueous solutions are those solutions where water is the solvent. An aqueous solution found in an equation describing a chemical reaction is denoted by the state symbol, (aq).
Conductivity is a measure of the ability of a material to conduct electric current.
Crystal water is water contained in certain salt crystals. It can be removed by heating. Crystals that contain crystal water are called hydrated and their salts hydrates.
Ionic conductor is a material that conducts electricity with ions as charge carriers.
Mineral water is a groundwater that rises to the surface through a natural opening in the earth or rock and contains a relatively high concentration of mineral ions and trace of elements which can be radioactive or thermal.
Deionised water is water from which ionic salts have been removed by ion-exchange. It is used for many purposes as an alternative to distilled water.
Type of water | Conductivity / µScm-1 |
---|---|
Ultrapure water | 0.05 |
Distilled water | 0.5 |
Tap water | 50 |
Ocean water | 50 000 |
Distilled water is water purified by distillation so as to free it from dissolved salts and other compounds. Distilled water in equilibrium with the carbon dioxide in the air has conductivity of about 0.8×10-6 S cm-1. Repeated distillation in vacuum can bring conductivity down to 0.043×10-6 S cm-1 at 18 °C. The limiting conductivity is due to self ionisation
Soft water is any water that does not contain large concentrations of the dissolved minerals calcium or magnesium.
Standard mean ocean water (SMOW) is a standard sample of pure water of accurately known isotopic composition which is maintained by the International Atomic Energy Agency. It is used for precise calibration of density and isotopic composition measurements.
Generalic, Eni. "Tvrdoća vode." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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Periodic Table