Nomenclature and Writing of Chemical Formulas

A compound is defined as a substance formed when two or more elements chemically combine in fixed proportions. This means that the elements interact at the molecular level, resulting in a new substance with unique properties that differ from those of the individual elements. For example, water (H2O) is a compound made of hydrogen and oxygen in a specific ratio. In contrast, a mixture does not have a fixed composition and retains the properties of its components, while a single element consists of only one type of atom.

An empirical formula represents the simplest whole-number ratio of the different types of atoms in a compound. Unlike molecular formulas, which indicate the actual number of each type of atom, empirical formulas reduce these numbers to their lowest terms. For example, the empirical formula for glucose (C6H12O6) is CH2O, reflecting the simplest ratio of carbon, hydrogen, and oxygen atoms. This makes the empirical formula a useful tool for understanding the basic composition of compounds without detailing their molecular structure.

KBr is the chemical formula for potassium bromide, which consists of potassium (K) and bromine (Br) ions. In this compound, potassium has a +1 charge, while bromine has a -1 charge, resulting in a neutral compound. The name "potassium bromide" reflects the presence of potassium and bromine in the form of a bromide ion. Other options, such as potassium bromate and potassium bromite, refer to different compounds with additional oxygen atoms, while "potassium bromine" incorrectly suggests a molecular form rather than an ionic compound.

In the Stock System of nomenclature, the oxidation state of a metal in a compound is indicated by placing Roman numerals in parentheses after the name of the metal. This method provides clarity regarding the specific charge of the metal ion, especially for transition metals that can exhibit multiple oxidation states. For example, in iron(III) chloride, the Roman numeral III indicates that iron has a +3 oxidation state. This system helps avoid confusion and ensures accurate communication of the compound's composition.

When hydrogen chloride (HCl) is dissolved in water, it forms hydrochloric acid. This is because the HCl molecules dissociate into hydrogen ions (H⁺) and chloride ions (Cl⁻), resulting in an acidic solution. Hydrochloric acid is a strong acid commonly used in laboratories and industry, and its name reflects the compound's behavior in aqueous solution, distinguishing it from hydrogen chloride, which is the gaseous form.

Hydrates are chemical compounds that incorporate water molecules into their structure in a specific ratio. These water molecules are not merely associated with the compound; they are integral to its crystalline form and properties. The presence of water affects the compound's stability, solubility, and reactivity. When hydrates are heated, they can lose these water molecules, resulting in anhydrous compounds. This characteristic makes hydrates important in various chemical applications, including pharmaceuticals, construction materials, and food preservation.

Binary molecular compounds consist of two different elements, both of which are non-metals. These compounds are formed through covalent bonding, where atoms share electrons to achieve stability. Common examples include water (H₂O) and carbon dioxide (CO₂). The term "binary" indicates that the compound contains only two types of atoms, distinguishing it from other compounds that may include metals or more than two elements. Thus, the statement accurately describes the composition of binary molecular compounds.

Sulfate is a polyatomic ion composed of one sulfur atom and four oxygen atoms, which gives it the chemical formula SO4²⁻. This indicates that the sulfate ion carries a -2 charge. The other options listed do not correctly match their respective polyatomic ions with their correct chemical symbols, making sulfate the only accurate pairing in the choices provided.