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The overall chemical reaction is: CO 2 + Ca(OH) 2 → CaCO 3 + H 2 O + heat (in the presence of water) Each mole of CO 2 (44 g) reacts with one mole of calcium hydroxide (74 g) and produces one mole of water (18 g). The reaction can be considered as a strong-base-catalysed, water-facilitated reaction. [5]
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:
Ca 0 Calcium: Gas Ca 178.2 Calcium(II) ion Gas Ca 2+ 1925.90 Calcium(II) ion Aqueous Ca 2+ −542.7 Calcium carbide: Solid CaC 2: −59.8 Calcium carbonate Solid CaCO 3: −1206.9 Calcium chloride: Solid CaCl 2: −795.8 Calcium chloride: Aqueous CaCl 2: −877.3 Calcium phosphate: Solid Ca 3 (PO 4) 2: −4132 Calcium fluoride: Solid CaF 2: − ...
The reaction Ca(OH) 2 + CO 2 ⇌ Ca 2+ + HCO − 3 + OH − illustrates the basicity of calcium hydroxide. Soda lime, which is a mixture of the strong bases NaOH and KOH with Ca(OH) 2, is used as a CO 2 absorbent.
Carbonatation is a slow process that occurs in concrete where lime (CaO, or Ca(OH) 2 ) in the cement reacts with carbon dioxide (CO 2) from the air and forms calcium carbonate. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5.
3 (s) + 3 H 2 O (g) The net reaction being: 2LiOH(s) + CO 2 (g) → Li 2 CO 3 (s) + H 2 O (g) Lithium peroxide can also be used as it absorbs more CO 2 per unit weight with the added advantage of releasing oxygen. [12] In recent years lithium orthosilicate has attracted much attention towards CO 2 capture, as well as energy storage. [8]
The standard enthalpy change for the first hydrolysis step is generally not very different from that of the dissociation of pure water. Consequently, the standard enthalpy change for the substitution reaction [M(H 2 O) n] z+ +OH − ⇌ :[M(H 2 O) n-1 (OH)] (z-1)+ + H 2 O. is close to zero.
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).