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Calcium hydroxide is moderately soluble in water, as seen for many dihydroxides. Its solubility increases from 0.66 g/L at 100 °C to 1.89 g/L at 0 °C. [8] Its solubility product K sp of 5.02 × 10 −6 at 25 °C, [1] its dissociation in water is large enough that its solutions are basic according to the following dissolution reaction:
Density: 2.2 g cm −3 [2] Solubility in H 2 O 0.160 20 g/100 g [2] pH (at 20 °C) ... -985.2 kJ/mol [4] Standard molar entropy, S o solid: 83.4 J/(mol K) [4] Heat ...
Tricalcium aluminate Ca 3 Al 2 O 6, often formulated as 3CaO·Al 2 O 3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates. It does not occur in nature, but is an important mineral phase in Portland cement .
Pentacalcium trialuminate, 5CaO·3Al 2 O 3 (C 5 A 3), forms only under an anhydrous and oxygen free atmosphere. The crystal is orthorhombic, with a density of 3067 kg·m −3. It reacts rapidly with water. Tetracalcium trialuminate, 4CaO·3Al 2 O 3 (C 4 A 3), is a metastable phase formed by dehydrating 4CaO·3Al 2 O 3 ·3H 2 O (C 4 A 3 H 3).
Calcium peroxide or calcium dioxide is the inorganic compound with the formula CaO 2. It is the peroxide (O 2 2−) salt of Ca 2+. Commercial samples can be yellowish, but the pure compound is white. It is almost insoluble in water. [3]
Its usage varies from about 30 to 50 kilograms (65–110 lb) per ton of steel. The quicklime neutralizes the acidic oxides, SiO 2, Al 2 O 3, and Fe 2 O 3, to produce a basic molten slag. [10] Ground quicklime is used in the production of aerated concrete such as blocks with densities of ca. 0.6–1.0 g/cm 3 (9.8–16.4 g/cu in). [10]
The replacement of one divalent Ca 2+ cation by a trivalent Al 3+ cation, or to a lesser extent by a Fe 3+ cation, with a Ca:Al ratio of 2:1 (one Al substituted for every 3 cations) causes an excess of positive charge in the sheet: 2[2Ca (OH) 2 ·(Al,Fe)(OH) 2] + to be compensated by 2 negative charges X –.
The formula, Cu 2 CO 3 (OH) 2 shows that it is halfway between copper carbonate and copper hydroxide. Indeed, in the past the formula was written as CuCO 3 ·Cu(OH) 2. The crystal structure is made up of copper, carbonate and hydroxide ions. [36] The mineral atacamite is an example of a basic chloride. It has the formula Cu 2 Cl(OH) 3.