Question

Write the chemical formulas for these substances: (a) slaked lime (e) cane sugar (b) fool's gold (f) borax (c) washing soda (g) wood alcohol (d) calcite (h) acetylene

Short answer

Slaked lime: Ca(OH)2, Cane sugar: C12H22O11, Fool's gold: FeS2, Borax: Na2B4O7·10H2O, Washing soda: Na2CO3·10H2O, Wood alcohol: CH3OH, Calcite: CaCO3, Acetylene: C2H2.

Step-by-step solution

Identifying Slaked Lime

Slaked lime is chemically known as calcium hydroxide. It's produced by adding water to quicklime (calcium oxide, CaO). The formula for slaked lime is therefore written as Ca(OH)2.

Identifying Cane Sugar

Cane sugar is also known as sucrose, which is a disaccharide composed of glucose and fructose. The chemical formula for cane sugar (sucrose) is C12H22O11.

Identifying Fool's Gold

Fool's gold is a common nickname for the mineral pyrite, which has a metallic luster and brass-yellow hue similar to gold. However, its chemical formula is quite different, and it is FeS2.

Identifying Borax

Borax is a mineral and a salt of boric acid, commonly used in cleaning products. The chemical formula for borax is Na2B4O7·10H2O.

Identifying Washing Soda

Washing soda refers to sodium carbonate decahydrate. Its chemical formula is Na2CO3·10H2O.

Identifying Wood Alcohol

Wood alcohol is another name for methanol, a simple alcohol. Its chemical formula is CH3OH.

Identifying Calcite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). Thus, its chemical formula is CaCO3.

Identifying Acetylene

Acetylene is a hydrocarbon and the simplest alkyne. Used as a fuel and a chemical building block, its formula is C2H2.

Key concepts

Calcium Hydroxide

Calcium hydroxide, often known as slaked lime, is an inorganic compound with widespread use in construction and industry. Its chemical formula is denoted by \( Ca(OH)_2 \), which indicates that each molecule of calcium hydroxide is composed of one calcium ion (Ca^2+) bonded to two hydroxide ions (OH^-).

Calcium hydroxide is produced through a chemical reaction called hydration, which involves adding water to calcium oxide (quicklime). This process releases heat in an exothermic reaction and results in a fine white powder that is slightly soluble in water. It is utilized to make plaster, cement, and mortar, and also serves in the water purification process and as a pH adjustment agent in soil.

Sucrose Structure

Sucrose, better known as table sugar or cane sugar, is a natural disaccharide made up of glucose and fructose molecules. The structural formula for sucrose is \( C_{12}H_{22}O_{11} \) and exhibits a unique feature among sugars: the glycosidic bond between glucose and fructose effectively hides their reactive carbonyl groups, making sucrose a non-reducing sugar.

This structure is important for understanding metabolism and fermentation processes, as it influences how sugars behave under various conditions. Sucrose is extracted from the sugar cane or sugar beet plants and is a primary sweetener used in food and beverage preparation.

Pyrite Composition

Pyrite, commonly known as fool's gold, has deceived many with its gold-like appearance. Nonetheless, its composition is distinct. Pyrite's chemical formula is \( FeS_2 \), indicating that each pyrite molecule consists of one iron (Fe) atom and two sulfur (S) atoms.

The structure of pyrite forms a cubic crystal system that sometimes resembles a dodecahedron. Iron and sulfur atoms in pyrite form a repeating pattern that creates its metallic luster and pale brass-yellow hue. While it has no gold content, pyrite is often found in gold-bearing regions and has various uses in the production of sulfuric acid and as an ore for iron.

Sodium Carbonate Decahydrate

Sodium carbonate decahydrate is a hydrated form of sodium carbonate, more comonnly known as washing soda. Its formula, \( Na_2CO_3\cdot10H_2O \), encompasses ten water molecules (decahydrate) for every sodium carbonate unit. This vividly illustrates its hygroscopic nature—its tendency to absorb moisture from the environment.

The compound has a significant role in domestic and industrial cleaning products by softening water and removing stains, grease, and dirt. Sodium carbonate decahydrate also acts as a key ingredient in glass making and is used in dyeing and printing in the textile industry due to its alkaline properties.

Methanol Formula

Methanol, colloquially known as wood alcohol, has the simplest structure among the alcohols. Its chemical formula is \( CH_3OH \), comprising one carbon atom connected to three hydrogen atoms and one hydroxyl group (-OH). This formation endows methanol with its characteristic properties as a polar solvent.

Methanol is a light, volatile, colorless, and flammable liquid with a distinct odor and is used in various applications such as a fuel, solvent, antifreeze, and as an important feedstock in chemical manufacturing. Due to its toxicity, methanol ingestion can be dangerous, causing symptoms from headache and dizziness to severe poisoning and death, thus making it unsuitable for consumption.