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Calcium carbonate reacts with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate. CaCO 3 (s) + CO 2 (g) + H 2 O(l) → Ca(HCO 3) 2 (aq) This reaction is important in the erosion of carbonate rock, forming caverns, and leads to hard water in many regions. An unusual form of calcium carbonate is the hexahydrate ...
One exception is phosphorus, for which the most stable form at 1 bar is black phosphorus, but white phosphorus is chosen as the standard reference state for zero enthalpy of formation. [2] For example, the standard enthalpy of formation of carbon dioxide is the enthalpy of the following reaction under the above conditions:
The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5. This highly alkaline environment is one in which the steel rebar is passivated and is protected from corrosion. According to the Pourbaix diagram for iron, the metal is passive when the pH is above 9.5. [1]
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.
These hard waters tend to form carbonate scale in pipes and boilers, and they react with soaps to form an undesirable scum. Attempts to prepare compounds such as solid calcium bicarbonate by evaporating its solution to dryness invariably yield instead the solid calcium carbonate: [1] Ca(HCO 3) 2 → CO 2 (g) + H 2 O(l) + CaCO 3 (s).
The following table gives the crystalline structure of the most thermodynamically stable form(s) for elements that are solid at standard temperature and pressure. Each element is shaded by a color representing its respective Bravais lattice, except that all orthorhombic lattices are grouped together.
The standard Gibbs free energy of formation (G f °) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C).
Although most compounds are referred to by their IUPAC systematic names (following IUPAC nomenclature), ... Water - H 2 O [204] He. Sodium helide – Na 2 He; I. In