定义Definition
氧化钙 CaO 俗称生石灰，是白色固体，熔点很高（约 2600 °C）。它是碱性氧化物，与水剧烈反应并大量放热生成氢氧化钙。工业上煅烧石灰石制得，用于建筑、冶金和作干燥剂。
Calcium oxide, CaO, known as quicklime, is a white solid with a very high melting point (about 2600 °C). It is a basic oxide that reacts vigorously with water, releasing much heat, to form calcium hydroxide. It is made by roasting limestone and used in building, metallurgy and as a drying agent.
主要反应Main reactions
制取：CaCO₃ → CaO + CO₂（约 900 °C）；与水：CaO + H₂O → Ca(OH)₂，放热，称为消化；与酸性氧化物：在炼钢和炼铁中与 SiO₂ 结合成炉渣，CaO + SiO₂ → CaSiO₃。
Preparation: CaCO₃ → CaO + CO₂ (about 900 °C). With water: CaO + H₂O → Ca(OH)₂, exothermic, called slaking. With acidic oxides: in iron- and steel-making it combines with SiO₂ to form slag, CaO + SiO₂ → CaSiO₃.
用作干燥剂As a drying agent
生石灰能吸收水分，常装在食品包装的小袋中防潮。由于它是碱性物质，可干燥氨气，但不能干燥 HCl、CO₂ 等酸性气体。
Quicklime absorbs water and is found in small sachets in food packaging. Because it is basic it can dry ammonia but not acidic gases such as HCl or CO₂.
化学性质Chemical properties
与水反应：CaO + H₂O → Ca(OH)₂（放热）
With water: CaO + H₂O → Ca(OH)₂ (exothermic)
与二氧化硅生成炉渣：CaO + SiO₂ → CaSiO₃
Forms slag with silica: CaO + SiO₂ → CaSiO₃