Calcium oxide is a crystalline compound of white color. Other names for this substance are quicklime, calcium oxide, "kirabit," "boiling water." Calcium oxide, the formula of which is CaO, and its product of interaction with (H2O) water - Ca (OH) 2 (fluff, or slaked lime) are widely used in the construction industry.
How to get calcium oxide?
1. The industrial method of obtaining this substance is the thermal (under the influence of temperature) decomposition of limestone (calcium carbonate) :
CaCO3 (limestone) = CaO (calcium oxide) + CO2 (carbon dioxide)
2. Also, calcium oxide can be obtained through the interaction of simple substances:
2Ca (calcium) + O2 (oxygen) = 2CaO (calcium oxide)
3. The third method for producing calcium oxide is the thermal decomposition of calcium hydroxide (Ca (OH) 2) and the calcium salts of several oxygen-containing acids:
2Ca (NO3) 2 (calcium nitrate) = 2CaO (obtained substance) + 4NO2 (nitric oxide) + O2 (oxygen)
Physical properties of calcium oxide
1. Appearance: white crystalline compound. It crystallizes like sodium chloride (NaCl) in a cubic crystal face-centered lattice.
2. The molar mass is 55.07 grams / mol.
3. The density is 3.3 grams / centimeter³.
Thermal properties of calcium oxide
1. The melting point is 2570 degrees
2. The boiling point is 2850 degrees
3. The molar heat capacity (under standard conditions) is 42.06 J / (mol · K)
4. The enthalpy of formation (under standard conditions) is -635 kJ / mol
Chemical properties of calcium oxide
Calcium oxide (CaO formula) is the main oxide. Therefore, he can:
- dissolve in water (H2O) with the release of energy. In this case, calcium hydroxide is formed. This reaction looks like this:
CaO (calcium oxide) + H2O (water) = Ca (OH) 2 (calcium hydroxide) + 63.7 kJ / mol;
- react with acids and acid oxides. In this case, salts are formed. Here are some examples of reactions:
CaO (calcium oxide) + SO2 (sulfur dioxide) = CaSO3 (calcium sulfite)
CaO (calcium oxide) + 2HCl (hydrochloric acid) = CaCl2 (calcium chloride) + H2O (water).
The use of calcium oxide:
1. The main volumes of the substance under consideration are used in the production of silicate brick in construction. Quicklime used to be used as lime cement. It was obtained by mixing it with water (H2O). As a result, calcium oxide turned into hydroxide, which then, absorbing carbon dioxide (CO2) from the atmosphere, hardened strongly, turning into calcium carbonate (CaCO3). Despite the cheapness of this method, at present lime cement is practically not used in construction, as it has the ability to absorb and accumulate fluids well.
2. As a refractory material, calcium oxide is suitable as an inexpensive and affordable material. Fused calcium oxide is resistant to water (H2O), which allowed it to be used as a refractory where the use of expensive materials is impractical.
3. The laboratories use higher calcium oxide to dry those substances that do not react with it.
4. In the food industry, this substance is registered as a food additive under the designation E 529. It is used as an emulsifier to create a homogeneous mixture of immiscible substances - water, oil and fat.
5. In industry, calcium oxide is used to remove sulfur dioxide (SO2) from flue gases. Apply, as a rule, a 15% aqueous solution. As a result of the reaction, in which hydrated lime and sulfur dioxide interact, gypsum CaCO4 and CaCO3 are obtained. When conducting experiments, scientists achieved an indicator of 98% purification of smoke from sulfur dioxide.
6. Used in special “self-heating” dishes. A container with a small amount of calcium oxide is located between the two walls of the vessel. When piercing the capsule in water, a reaction begins with the release of a certain amount of heat.