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Hard water usually contains calcium or magnesium ions. Sodium carbonate is used for removing these ions and replacing them with sodium ions. [16] Sodium carbonate is a water-soluble source of carbonate. The calcium and magnesium ions form insoluble solid precipitates upon treatment with carbonate ions:
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 tables below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams of substance per 100 millilitres of water (g/100 ml), unless shown otherwise. The substances are listed in alphabetical order.
Group 1: Alkali metals Reaction of sodium (Na) and water Reaction of potassium (K) in water. The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table - they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
Electrode potentials of successive elementary half-reactions cannot be directly added. However, the corresponding Gibbs free energy changes (∆G°) must satisfy ∆G° = – z FE°, where z electrons are transferred, and the Faraday constant F is the conversion factor describing Coulombs transferred per mole electrons. Those Gibbs free energy ...
To avoid scaling in water cooled heat exchangers, water is treated by lime and or soda ash to remove the water hardness. The following chemical reactions take place in lime soda softening process which precipitates the calcium and magnesium salts as calcium carbonate and magnesium hydroxide which have very low solubility in water.
The very pure and finely divided precipitate of calcium carbonate that is generated is a valuable by-product used in the manufacture of toothpaste. The salting-out process used in the manufacture of soaps benefits from the common-ion effect. Soaps are sodium salts of fatty acids. Addition of sodium chloride reduces the solubility of the soap salts.
The net reaction between an aldehyde (or an alpha-hydroxy-ketone) and the copper(II) ions in Benedict's solution may be written as: RCHO + 2 Cu 2+ + 5 OH − → RCOO − + Cu 2 O + 3 H 2 O. The hydroxide ions in the equation forms when sodium carbonate dissolves in water. With the citrate included, the reaction becomes: