Question

Many familiar substances have common, unsystematic names. For each of the following, give the correct systematic name: (a) saltpeter, \(\mathrm{KNO}_{3} ;(\mathbf{b})\) soda ash, \(\mathrm{Na}_{2} \mathrm{CO}_{3} ;(\mathbf{c})\) lime, \(\mathrm{CaO} ;(\mathbf{d})\) muriatic acid, HCl; \((\mathbf{e})\) Epsom salts, \(\mathrm{MgSO}_{4} ;\) (f) milk of magnesia, \(\mathrm{Mg}(\mathrm{OH})_{2}\)

Short answer

(a) Potassium nitrate; (b) Sodium carbonate; (c) Calcium oxide; (d) Hydrochloric acid; (e) Magnesium sulfate; (f) Magnesium hydroxide.

Step-by-step solution

Identifying the compound in a chemical formula

Each of these chemical compounds is commonly known by a colloquial name that doesn't reflect the actual chemical formula. The problem provides both the informal name and the formula, and we need to convert them to their systematic chemical names.

Systematic naming for KNO3

Saltpeter, which is \(\mathrm{KNO}_{3}\), is systematically named potassium nitrate. Potassium is the cation and nitrate is the anion.

Systematic naming for Na2CO3

Soda ash, represented by \(\mathrm{Na}_{2} \mathrm{CO}_{3}\), is called sodium carbonate in systematic nomenclature. Sodium ions are paired with carbonate ions.

Systematic naming for CaO

Lime, or \(\mathrm{CaO}\), is systematically named calcium oxide. Calcium ions combine with oxide ions.

Systematic naming for HCl

Muriatic acid, represented by HCl, is more formally called hydrogen chloride when an anhydrous gas and hydrochloric acid when in aqueous form.

Systematic naming for MgSO4

Epsom salts, \(\mathrm{MgSO}_{4}\), are known in systemic terms as magnesium sulfate. Magnesium ions are associated with sulfate ions.

Systematic naming for Mg(OH)2

Milk of magnesia, represented by \(\mathrm{Mg}( m{OH})_{2}\), is called magnesium hydroxide systematically. It consists of magnesium ions and hydroxide ions.

Key concepts

Chemical Formulas

Chemical formulas are shorthand representations of chemical compounds, giving insight into the composition and ratios of elements within them. They use symbols from the periodic table to denote each element. For instance, in \[C_aO\], the formula tells us that the compound consists of calcium and oxygen in a 1-to-1 ratio.

• Subscripts are used to show the number of atoms of each element present in one molecule of a compound. For example, \[\mathrm{Na}_2 \mathrm{CO}_3\] indicates there are two sodium (Na) atoms, one carbon (C) atom, and three oxygen (O) atoms.
• In compounds like \[\mathrm{KNO}_3\], the absence of subscript next to a letter implies there is one atom of that element.

Understanding chemical formulas is a key step for identifying compound components and how elements combine to form various substances.

Cation and Anion Identification

In ionic compounds, identification of cations and anions is crucial. Cations are the positively charged ions, while anions are negatively charged.

• For example, in \( \mathrm{MgSO}_4 \), the cation is the magnesium ion (\( \mathrm{Mg}^{2+} \)), and the anion is the sulfate ion (\( \mathrm{SO}_4^{2-} \)).
• In \( \mathrm{KNO}_3 \), potassium (\( \mathrm{K}^+ \)) acts as the cation, and the nitrate ion (\( \mathrm{NO}_3^- \)) is the anion.

The process of identifying these ions is key to understanding how ionic compounds are structured and how they behave in reactions.

Common vs. Systematic Names

While common names are often rooted in historical or cultural contexts, systematic names are derived using established conventions set by IUPAC (International Union of Pure and Applied Chemistry).

• For instance, 'lime' is the common name for \( \mathrm{CaO} \), but its systematic name is calcium oxide.
• 'Muriatic acid' refers to hydrochloric acid in liquid form.

Systematic names follow specific rules and often provide information about the composition and properties of the compound, unlike common names, which can sometimes be misleading or non-descriptive of the chemical makeup.

Chemical Reactions

Chemical reactions involve the transformation of substances through breaking and forming chemical bonds, resulting in new compounds.

• An example is when sodium carbonate (systematic name for soda ash, \( \mathrm{Na}_2 \mathrm{CO}_3 \)) reacts with hydrochloric acid, forming salt, carbon dioxide, and water.
• These reactions are governed by the law of conservation of mass, meaning the mass of the reactants equals the mass of the products.

Understanding the reactants and products involved in chemical reactions is crucial for predicting the outcome of chemical processes.

Ionic Compounds

Ionic compounds are formed when cations and anions are held together by electrostatic forces known as ionic bonds. They usually form between metals and non-metals.

• An example is potassium nitrate (systematic name for saltpeter, \( \mathrm{KNO}_3 \)), where potassium ions and nitrate ions bond ionically.
• Ionic compounds typically have high melting and boiling points due to strong ionic bonds.
• They are often soluble in water and conduct electricity when dissolved or melted, as ions move freely to conduct electrical current.

Recognizing and understanding ionic compounds is important in fields ranging from chemistry to materials science.