📚 Some Uses of Group 2 Compounds | 第2族化合物的若干用途
The Group 2 elements – beryllium, magnesium, calcium, strontium, barium and radium – are known as the alkaline earth metals. Although beryllium is somewhat atypical and radium is radioactive, the compounds of magnesium, calcium, strontium and barium have widespread industrial, agricultural, medical and constructional applications. Their oxides, hydroxides, carbonates, sulfates and chlorides exhibit properties such as basicity, low solubility or thermal stability that make them especially useful.
第2族元素——铍、镁、钙、锶、钡和镭——统称为碱土金属。尽管铍的性质略显反常且镭具有放射性，但镁、钙、锶、钡的化合物在工业、农业、医疗和建筑领域有着广泛的应用。它们的氧化物、氢氧化物、碳酸盐、硫酸盐和氯化物表现出碱性、低溶解度或热稳定性等性质，使其格外实用。
1. Introduction to Group 2 Compounds | 第2族化合物简介
The metals of Group 2 typically form ionic compounds with oxidation state +2. Common anions include oxide (O²⁻), hydroxide (OH⁻), carbonate (CO₃²⁻), sulfate (SO₄²⁻) and chloride (Cl⁻). Many of these compounds are white solids, and their solubility in water tends to decrease down the group for sulfates and hydroxides, while the solubility of hydroxides increases down the group. These trends influence their uses.
第2族金属通常形成氧化态为+2的离子化合物。常见的阴离子包括氧离子 (O²⁻)、氢氧根 (OH⁻)、碳酸根 (CO₃²⁻)、硫酸根 (SO₄²⁻) 和氯离子 (Cl⁻)。这些化合物多为白色固体，其硫酸盐和氢氧化物的溶解度通常沿族自上而下降低，而氢氧化物的溶解度则沿族自上而下升高。这些趋势影响着它们的用途。
2. Agricultural Use of Calcium Carbonate (Limestone) | 碳酸钙（石灰石）的农业用途
Finely ground limestone (CaCO₃) is spread on fields as agricultural lime to neutralise acidic soils. Soil acidity arises from acid rain and the use of nitrogenous fertilisers, which lower pH and reduce crop yields. Calcium carbonate reacts with hydrogen ions: CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂. This raises the soil pH and supplies soluble calcium, which improves soil structure and nutrient availability.
将石灰石 (CaCO₃) 研磨成细粉，作为农业石灰撒施到田地中，用于中和酸性土壤。酸雨和氮肥的使用会引发土壤酸化，降低pH值并减少作物产量。碳酸钙与氢离子反应：CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂。此反应提高了土壤pH值，并提供可溶性钙，改善土壤结构和养分有效性。
3. Calcium Oxide and Calcium Hydroxide in Construction | 氧化钙与氢氧化钙在建筑中的应用
Heating limestone produces quicklime (CaO). When water is added, it slakes vigorously to form slaked lime (Ca(OH)₂), releasing heat: CaO + H₂O → Ca(OH)₂. Slaked lime is mixed with sand and water to make lime mortar. As the mortar sets, it slowly absorbs carbon dioxide from the air and forms calcium carbonate: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. This process binds the sand grains together, producing a hard, durable building material.
加热石灰石可制得生石灰 (CaO)。加水后，生石灰剧烈熟化生成熟石灰 (Ca(OH)₂)，并释放热量：CaO + H₂O → Ca(OH)₂。熟石灰与砂、水拌合可制成石灰砂浆。砂浆在硬化过程中，缓慢吸收空气中的二氧化碳，生成碳酸钙：Ca(OH)₂ + CO₂ → CaCO₃ + H₂O。这一过程将砂粒粘结在一起，形成坚硬、耐久的建筑材料。
4. Magnesium Hydroxide as an Antacid | 氢氧化镁用作抗酸剂
A suspension of magnesium hydroxide in water, often called milk of magnesia, is a widely used antacid. It neutralises excess stomach acid (hydrochloric acid) gently, without producing gas that would cause discomfort. The reaction is: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O. Magnesium hydroxide is only slightly soluble in water, so it reacts slowly and provides a sustained relief from indigestion and heartburn.
氢氧化镁在水中的悬浮液——常被称为镁乳——是一种广泛使用的抗酸剂。它能温和中和胃中过量的盐酸，且不产生会引起不适的气体。反应式为：Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O。氢氧化镁仅微溶于水，因此反应缓慢，能持续缓解消化不良和胃灼热。
5. Calcium Hydroxide in Agriculture and Waste Treatment | 氢氧化钙在农业和废水处理中的应用
Calcium hydroxide is more soluble than calcium carbonate and is therefore faster-acting in neutralising acidic conditions. It is used to raise the pH of acidic soils and to treat acidic industrial effluents. In water treatment, Ca(OH)₂ precipitates toxic heavy metal ions as their insoluble hydroxides. It is also employed in the sugar industry to remove impurities from cane juice.
氢氧化钙的溶解度高于碳酸钙，因此能更快地中和酸性环境。它用于提高酸性土壤的pH值，并处理酸性工业废水。在水处理中，Ca(OH)₂ 可使有毒重金属离子以不溶性氢氧化物形式沉淀。制糖工业也使用氢氧化钙去除甘蔗汁中的杂质。
6. Barium Sulfate in Medical Imaging | 硫酸钡在医学成像中的应用
Barium sulfate (BaSO₄) is given to patients as a barium meal before X-ray examinations of the digestive tract. It is highly opaque to X‑rays, providing excellent contrast images. Although barium ions (Ba²⁺) are toxic, barium sulfate is extremely insoluble in water and body fluids, and is therefore safe to swallow. It passes through the gut without being absorbed.
在对患者进行消化道X射线检查之前，会让患者服用硫酸钡 (BaSO₄) 作为钡餐。硫酸钡对X射线高度不透，可提供良好的对比图像。虽然钡离子 (Ba²⁺) 有毒，但硫酸钡在水和体液中极难溶解，因此可以安全吞服。它能通过肠道而不被吸收。
7. Magnesium Oxide as a Refractory Material | 氧化镁作为耐火材料
Magnesium oxide (MgO) has an exceptionally high melting point of approximately 2852 °C. This makes it an ideal refractory material for lining furnaces, kilns and incinerators. It is also used to make crucibles for melting metals and in fire-resistant building boards. Its thermal stability and chemical inertness at high temperatures underpin these applications.
氧化镁 (MgO) 的熔点极高，约为2852 °C。这使其成为炉衬、窑炉内衬和焚烧炉的理想耐火材料。它还用于制造熔化金属的坩埚和防火建筑板材。其高温下的热稳定性和化学惰性是这些应用的基础。
8. Calcium Chloride for De-icing and Dust Control | 氯化钙用于除冰和粉尘控制
Anhydrous calcium chloride (CaCl₂) and its hydrates are highly deliquescent, absorbing moisture from the air. When spread on icy roads, CaCl₂ dissolves and lowers the freezing point of water, effectively melting ice at temperatures well below 0 °C. It is also sprayed on unpaved roads and construction sites to suppress dust by retaining moisture.
无水氯化钙 (CaCl₂) 及其水合物极易潮解，能从空气中吸收水分。将氯化钙撒在结冰道路上时，它溶解并降低水的冰点，可在远低于0 °C的温度下有效融化冰层。它还喷洒在未铺砌的道路和建筑工地上，通过保持水分来抑制扬尘。
9. Magnesium in the Extraction of Titanium | 镁在钛的提取中的应用
Titanium is extracted from its principal ore, rutile (TiO₂), via the Kroll process. The ore is first converted to titanium(IV) chloride (TiCl₄) and then reduced with molten magnesium under an inert atmosphere: TiCl₄ + 2Mg → Ti + 2MgCl₂. Magnesium acts as a powerful reducing agent, and the magnesium chloride by‑product is removed by distillation, leaving titanium sponge.
钛是通过克罗尔法从其主要矿石金红石 (TiO₂) 中提取的。首先将矿石转化为四氯化钛 (TiCl₄)，然后在惰性气氛中用熔融镁还原：TiCl₄ + 2Mg → Ti + 2MgCl₂。镁作为强还原剂，副产物氯化镁通过蒸馏除去，留下海绵钛。
10. Strontium Compounds in Fireworks | 锶化合物在焰火中的应用
Strontium salts, such as strontium nitrate (Sr(NO₃)₂) and strontium carbonate (SrCO₃), impart a characteristic deep‑red colour to flames. This is caused by the excitation and subsequent relaxation of electrons in the Sr²⁺ ions. Strontium‑based compositions are therefore essential for producing red colours in fireworks and signal flares.
硝酸锶 (Sr(NO₃)₂) 和碳酸锶 (SrCO₃) 等锶盐可使火焰呈现出特有的深红色。这是由于 Sr²⁺ 离子中的电子激发和随后的弛豫所致。因此，锶基配方对于在烟火和信号弹中产生红色是必不可少的。
11. Barium Compounds in Pyrotechnics and Rodenticide | 钡化合物在烟火和灭鼠药中的应用
Barium nitrate (Ba(NO₃)₂) and barium chloride (BaCl₂) are used in fireworks to produce a bright green colour, as Ba²⁺ ions emit light in the green region when heated. Moreover, barium carbonate (BaCO₃), although insoluble in water, dissolves in the hydrochloric acid of the stomach, releasing toxic Ba²⁺ ions. This property has been exploited in rodent baits.
硝酸钡 (Ba(NO₃)₂) 和氯化钡 (BaCl₂) 用于焰火中，产生明亮的绿色，因为 Ba²⁺ 离子受热时在绿光区域发光。此外，碳酸钡 (BaCO₃) 虽不溶于水，但会溶解在胃酸（盐酸）中，释放出有毒的 Ba²⁺ 离子。这一性质曾被利用于鼠药中。
12. Summary of Key Uses | 关键用途总结
The table below compiles the principal applications of Group 2 compounds along with the underlying reasons.
下表汇编了第2族化合物的主要用途及其背后的原因。
| Compound | Use | Reason for suitability |
|---|---|---|
| CaCO₃ | Agricultural lime | Neutralises soil acidity; supplies calcium |
| CaO / Ca(OH)₂ | Mortar, plaster | Sets by absorbing CO₂; forms strong carbonate matrix |
| Mg(OH)₂ | Antacid | Gently neutralises HCl; low solubility ensures slow action |
| BaSO₄ | Barium meal / X‑ray contrast | Highly insoluble, non‑toxic; absorbs X‑rays |
| MgO | Refractory linings | Very high melting point; thermally stable |
| CaCl₂ | De‑icing, dust control | Deliquescent; lowers freezing point of water |
| Mg | Extraction of Ti | Strong reducing agent (Kroll process) |
| Sr(NO₃)₂, SrCO₃ | Fireworks (red) | Sr²⁺ emits red light in a flame |
| Ba(NO₃)₂, BaCO₃ | Fireworks (green), rodenticide | Ba²⁺ emits green light; BaCO₃ releases toxic Ba²⁺ in stomach acid |
These examples highlight how the chemical properties of Group 2 compounds – acid–base behaviour, solubility patterns and thermal stability – determine their practical applications.
这些例子凸显了第2族化合物的化学性质——酸碱性、溶解度规律和热稳定性——如何决定其实际应用。
Published by TutorHao | Chemistry Revision Series | aleveler.com
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