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Heat: Quicklime releases thermal energy by the formation of the hydrate, calcium hydroxide, by the following equation: [11] CaO (s) + H 2 O (l) ⇌ Ca(OH) 2 (aq) (ΔH r = −63.7 kJ/mol of CaO) As it hydrates, an exothermic reaction results and the solid puffs up.
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]
For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The enthalpy of reaction can then be analyzed by applying Hess' law, which states that the sum of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction.
The reaction of calcium carbide with water, producing acetylene and calcium hydroxide, [5] was discovered by Friedrich Wöhler in 1862. CaC 2 ( s ) + 2H 2 O ( l ) → C 2 H 2 ( g ) + Ca(OH) 2 (aq) This reaction was the basis of the industrial manufacture of acetylene , and is the major industrial use of calcium carbide.
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).
Calcium nitride is formed along with the oxide, CaO, when calcium burns in air. It can be produced by direct reaction of the elements: [3] 3 Ca + N 2 → Ca 3 N 2. It reacts with water or even the moisture in air to give ammonia and calcium hydroxide: [4] Ca 3 N 2 + 6 H 2 O → 3 Ca(OH) 2 + 2 NH 3
Ca(OH) 2 or CaO · H 2 O: Calcium hydroxide (portlandite) C-S-H: 0.6–2.0 CaO · SiO 2 · 0.9–2.5 H 2 O, with variable composition within this range, and often also incorporating partial substitution of Al for Si: Calcium silicate hydrate: C-A-H: Phase more complex than C-S-H: Calcium aluminate hydrate C-A-S-H: This is even more complex than ...
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.