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The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
The solubility of gas obeys Henry's law, that is, the amount of a dissolved gas in a liquid is proportional to its partial pressure. Therefore, placing a solution under reduced pressure makes the dissolved gas less soluble. Sonication and stirring under reduced pressure can usually enhance the efficiency.
Substances that are hydrophobic ('water-fearing') do not dissolve well in water, whereas those that are hydrophilic ('water-friendly') do. An example of a hydrophilic substance is sodium chloride. In an aqueous solution the hydrogen ions (H +) and hydroxide ions (OH −) are in Arrhenius balance ([H +] [OH −] = K w = 1 x 10 −14 at 298 K).
Iron dissolved in groundwater is in the reduced iron II form. If this groundwater comes in contact with oxygen at the surface, e.g. in natural springs, iron II is oxidised to iron III and forms insoluble hydroxides in water. [7] The natural analogue of iron(II) hydroxide compound is the very rare mineral amakinite, (Fe,Mg)(OH) 2. [8] [9]
For example, carbon dioxide gas dissolves in water to produce a solution that contains hydronium, carbonate, and hydrogen carbonate ions. [ citation needed ] Molten salts can also be electrolytes as, for example, when sodium chloride is molten, the liquid conducts electricity.
In physical chemistry, Henry's law is a gas law that states that the amount of dissolved gas in a liquid is directly proportional at equilibrium to its partial pressure above the liquid. The proportionality factor is called Henry's law constant. It was formulated by the English chemist William Henry, who studied the topic in the early 19th ...
When metallic iron (oxidation state 0) is placed in a solution of hydrochloric acid, iron(II) chloride is formed, with release of hydrogen gas, by the reaction Fe 0 + 2 H + → Fe 2+ + H 2. Iron(II) is oxidized by hydrogen peroxide to iron(III), forming a hydroxyl radical and a hydroxide ion in the process. This is the Fenton reaction.
Iron(II) sulfate outside a titanium dioxide factory in Kaanaa, Pori, Finland. Upon dissolving in water, ferrous sulfates form the metal aquo complex [Fe(H 2 O) 6] 2+, which is an almost colorless, paramagnetic ion. On heating, iron(II) sulfate first loses its water of crystallization and the original green crystals are converted into a white ...