Common Names and Chemical Formulas

Limestone, marble, and chalk are all composed primarily of calcium carbonate, which has the chemical formula CaCO₃. Despite their different physical properties and formations—limestone being sedimentary, marble being metamorphic, and chalk being a type of limestone—they all consist of the same basic chemical compound. This commonality in composition is what makes the statement true. Each type has unique characteristics due to variations in their formation processes and impurities, but fundamentally, they share the same chemical structure.

Na₂CO₃·10H₂O is commonly known as washing soda or soda crystals. This compound is a hydrated form of sodium carbonate, featuring ten water molecules associated with each sodium carbonate unit. It is widely used in household cleaning products, laundry detergents, and as a water softener. The name "washing soda" reflects its primary application in cleaning, where it helps to remove stains and soften water, making it more effective for washing clothes.

Calcium carbonate (CaCO₃) is a common compound found in various geological formations. Limestone is primarily composed of CaCO₃ and forms from the accumulation of marine organisms. Marble, a metamorphic rock, originates from limestone and retains its calcium carbonate composition. Chalk, a soft, white, porous form of limestone, is also made up of CaCO₃. In contrast, gypsum, which has the chemical formula CaSO₄·2H₂O, does not contain calcium carbonate, making it distinct from the other three substances.

Epsom salt is indeed chemically known as magnesium sulfate heptahydrate, represented by the formula MgSO₄·7H₂O. This indicates that each molecule of magnesium sulfate is associated with seven water molecules, which is characteristic of its crystalline form. Epsom salt is commonly used in baths for its therapeutic properties, as well as in gardening and agriculture to provide magnesium and sulfur, essential nutrients for plant growth. The presence of water molecules in its structure contributes to its solubility and efficacy in various applications.

Green vitriol, commonly known as iron(II) sulfate heptahydrate, has the chemical formula FeSO₄·7H₂O. It is a hydrated form of iron(II) sulfate, characterized by the presence of seven water molecules associated with each formula unit of iron sulfate. This compound is often used in various applications, including as a reducing agent in chemical reactions, in water treatment processes, and as a supplement in agriculture to provide iron to plants. The distinctive green color of the crystals is due to the presence of iron in the ferrous state.

CuSO₄·5H₂O is commonly known as blue vitriol due to its distinctive blue color, which is a result of the copper sulfate's hydrated form. This compound is often used in various applications, including agriculture as a fungicide and in chemistry as a reagent. The term "vitriol" historically refers to sulfate minerals, and the blue color is characteristic of copper salts, distinguishing it from other sulfate compounds.

Milk of magnesia is a suspension of magnesium hydroxide, which is represented by the chemical formula Mg(OH)₂. This compound consists of magnesium ions (Mg²⁺) and hydroxide ions (OH⁻). It is commonly used as an antacid to neutralize stomach acid and as a laxative. The formula indicates that each molecule of magnesium hydroxide contains one magnesium atom and two hydroxide groups, reflecting its basic properties and effectiveness in treating digestive issues.

Vinegar is primarily composed of acetic acid, which has the chemical formula CH₃COOH. This formula indicates that each molecule consists of two carbon atoms, four hydrogen atoms, and two oxygen atoms. Acetic acid is responsible for the sour taste and pungent smell of vinegar, making it a common ingredient in cooking and food preservation. The other options represent different compounds: C₂H₅OH is ethanol, HCOOH is formic acid, and H₂SO₄ is sulfuric acid, none of which are vinegar.

Common salt, known scientifically as sodium chloride, has the chemical formula NaCl. It consists of sodium (Na) ions and chloride (Cl) ions in a 1:1 ratio, forming an ionic compound. This compound is widely used in food seasoning and preservation, as well as in various industrial applications. The simplicity of its formula reflects the basic nature of the compound, which is essential for human health and is one of the most common salts found in nature.

Ca(OH)₂ is commonly known as slaked lime, which is produced by adding water to quicklime (CaO). This process, called slaking, results in a white, powdery substance that is used in various applications, including construction, water treatment, and agriculture. Slaked lime is an important chemical in many industrial processes due to its ability to neutralize acidity and its effectiveness as a building material. Unlike quicklime, which is caustic and reactive, slaked lime is more stable and safer to handle, making it widely utilized in various sectors.

Quick lime, also known as calcium oxide, is produced by heating limestone (calcium carbonate) in a process called calcination. The chemical formula CaO indicates that each molecule consists of one calcium atom (Ca) and one oxygen atom (O). This compound is highly reactive and is commonly used in various industrial processes, including steel production, water treatment, and as a drying agent. Its strong basic properties make it essential in chemical reactions, particularly in neutralizing acids.

KOH is commonly known as caustic potash, which is a strong alkaline compound used in various applications, including agriculture and industrial processes. It is the potassium salt of hydroxide and is highly soluble in water. This compound is often used as a fertilizer, in soap making, and in chemical manufacturing. The term "caustic" indicates its ability to corrode or burn organic tissue, which is characteristic of strong bases. Thus, caustic potash is a widely recognized name in both chemical and agricultural contexts.

Caustic soda, commonly known as sodium hydroxide, has the chemical formula NaOH. It consists of sodium (Na), oxygen (O), and hydrogen (H) atoms. This strong alkaline compound is widely used in various industrial processes, including soap making, paper production, and water treatment. Its properties make it effective for neutralizing acids and as a cleaning agent. The other options listed, such as KOH (potassium hydroxide) and Ca(OH)₂ (calcium hydroxide), are different compounds with distinct chemical properties and uses.

Gypsum is a naturally occurring mineral composed of calcium sulfate dihydrate. Its chemical formula, CaSO₄·2H₂O, indicates that each formula unit contains one calcium ion (Ca²⁺), one sulfate ion (SO₄²⁻), and two water molecules (H₂O). This structure is crucial for its properties and applications in construction, agriculture, and various industrial processes. The presence of water in its formula distinguishes gypsum from anhydrite, which is calcium sulfate without water. Thus, the statement accurately reflects the chemical composition of gypsum.

CaSO₄·½H₂O is commonly known as Plaster of Paris because it is produced by heating gypsum (CaSO₄·2H₂O) to remove water. This process creates a fine powder that, when mixed with water, forms a paste that hardens quickly. Plaster of Paris is widely used in construction, art, and medical applications due to its quick-setting properties and versatility. Its name comes from the large deposits of gypsum found in Paris, which were historically used for this purpose.

Bleaching powder, commonly used as a disinfectant and bleaching agent, has the chemical formula CaOCl₂. This formula indicates that it is composed of calcium (Ca), oxygen (O), and chlorine (Cl) atoms. Specifically, it consists of one calcium atom, two oxygen atoms, and two chlorine atoms. The presence of chlorine gives bleaching powder its strong oxidizing properties, making it effective for sanitizing water and whitening textiles. Its chemical structure is essential for its various applications in household cleaning and industrial processes.

Washing soda, commonly used in cleaning and laundry, is chemically known as sodium carbonate decahydrate. Its formula, Na₂CO₃·10H₂O, indicates that it consists of two sodium (Na) ions, one carbonate (CO₃) ion, and ten water molecules (H₂O) associated with each formula unit. This hydration contributes to its properties, making it effective in softening water and enhancing the cleaning process. The presence of water molecules distinguishes it from other sodium compounds, such as sodium bicarbonate (baking soda) and sodium chloride (table salt).

NaHCO₃, or sodium bicarbonate, is commonly known as baking soda. It is a versatile compound often used in cooking as a leavening agent, helping baked goods rise by producing carbon dioxide when combined with acids. Additionally, baking soda has various household applications, including acting as a mild abrasive, deodorizer, and pH regulator. Its widespread use in kitchens and its role in baking have solidified its common name as baking soda, distinguishing it from other sodium compounds like washing soda and caustic soda.