Question

Write formulas for these compounds: (a) silver sulfite (i) potassium (b) cobalt(II) bromide permanganate (c) tin(II) hydroxide (j) arsenic(V) sulfite (d) aluminum sulfate (k) sodium peroxide (e) lead(II) chloride (1) iron(II) sulfate (f) ammonium carbonate (m) potassium dichromate (g) chromium(III) oxide (n) bismuth(III) chromate (h) copper(II) chloride

Short answer

Ag2SO3, CoBr2, Sn(OH)2, As2(SO3)3, Al2(SO4)3, PbCl2, FeSO4, Cr2O3, CuCl2, KMnO4, Na2O2, (NH4)2CO3, K2Cr2O7, Bi2(CrO4)3

Step-by-step solution

Writing the Formula for Silver Sulfite

The formula for silver sulfite can be obtained by combining silver (Ag) with sulfite (SO3). Silver has a +1 charge and sulfite has a -2 charge. To balance the charges, two silver ions will be needed for one sulfite ion. The formula is Ag2SO3

Writing the Formula for Cobalt(II) Bromide

Cobalt(II) means cobalt has a +2 charge. Bromide has a -1 charge. Two bromide ions will be required for each cobalt ion to balance the charges. The formula is CoBr2.

Writing the Formula for Tin(II) Hydroxide

Tin(II) indicates that tin has a +2 charge. Hydroxide carries a -1 charge. It will require two hydroxide ions to balance the charge of one tin ion. The formula is Sn(OH)2.

Writing the Formula for Arsenic(V) Sulfite

Arsenic(V) indicates arsenic with a +5 charge. Sulfite is SO3 with a -2 charge. To neutralize, one would need three sulfite ions for each arsenic ion. The formula is As2(SO3)3.

Writing the Formula for Aluminum Sulfate

Aluminum has a +3 charge and sulfate (SO4) a -2 charge. To balance, two aluminum ions for each three sulfate ions are required, giving the formula Al2(SO4)3.

Writing the Formula for Lead(II) Chloride

Lead(II) has a +2 charge and chloride a -1 charge. Two chloride ions would balance out the charge of one lead ion, yielding the formula PbCl2.

Writing the Formula for Iron(II) Sulfate

Iron(II) has a +2 charge, and sulfate has a -2 charge. A one-to-one ratio balances the charge, resulting in the formula FeSO4.

Writing the Formula for Chromium(III) Oxide

Chromium(III) signifies a +3 charge on the chromium, and oxide has a -2 charge. To balance the charges, two chromium ions will be needed for every three oxide ions. The molecular formula is Cr2O3.

Writing the Formula for Copper(II) Chloride

Copper(II) has a +2 charge and chloride has a -1 charge. We will need two chloride ions for one copper ion to balance out the charges, giving the formula CuCl2.

Additional Compounds

The following compounds follow similar steps for determining their formulas: (i) Potassium permanganate - KMnO4, (k) Sodium peroxide - Na2O2, (f) Ammonium carbonate - (NH4)2CO3, (m) Potassium dichromate - K2Cr2O7, (n) Bismuth(III) chromate - Bi2(CrO4)3.

Key concepts

Naming Ionic Compounds

Understanding how to name ionic compounds is crucial for students as it forms the basis of chemistry communication. Ionic compounds consist of positive and negative ions that are held together by electrostatic forces. The name of an ionic compound is derived from the names of these ions.

Positive ions, also known as cations, are usually metals or polyatomic ions with positive charges. Negative ions, anions, are nonmetals or polyatomic ions with negative charges. When naming an ionic compound, the cation name is given first followed by the anion name. For transition metals and some other metals that can form more than one cation with different charges, the charge is specified by a Roman numeral in parentheses after the cation name.

For example:

• Cobalt(II) bromide — Here, 'Cobalt(II)' indicates that cobalt has a +2 charge.
• Tin(II) hydroxide — 'Tin(II)' shows that tin has a +2 charge.

This naming convention communicates the chemical composition of the compound clearly and allows chemists to infer the possible properties and reactivities of the compound.

Balancing Ionic Charges

Balancing ionic charges is essential in forming correct chemical formulas for ionic compounds. An ionic compound must be electrically neutral, which means the total positive charge must cancel out the total negative charge. This requires pairing the cations and anions in ratios that achieve charge balance.

To find the right ratio, look at the charges of the cation and anion. The number of ions needed for each will be in the inverse ratio of the charges. For example, if a cation has a charge of +2 and an anion has a charge of -1, like in cobalt(II) bromide (CoBr2), it will require two bromides to balance one cobalt.

Common Steps to Balance Ionic Charges:

• Identify the charge on the cation and anion.
• Determine the least common multiple of these charges.
• Use the multiples to find the ratio of ions needed to balance the charges.

This procedure ensures that the chemical formula reflects a neutral compound, a principle that's universally followed in chemistry.

Inorganic Compound Nomenclature

Inorganic compound nomenclature involves a set of rules to systematically name compounds. It's a fundamental skill in chemistry that enables clear communication regarding the composition of a compound. There are different types of inorganic compounds including salts, oxides, acids, and base anhydrides.

To name an inorganic compound, one must consider several factors, such as the presence of metals, nonmetals, the oxidation state of the elements, and specific naming rules for polyatomic ions. The International Union of Pure and Applied Chemistry (IUPAC) provides the guidelines for naming these compounds.

Key Points on Inorganic Nomenclature:

• Metallic elements in compounds typically retain their element name.
• The oxidation state of a metal in a compound can change and is indicated with Roman numerals.
• Nonmetallic elements may have their ending changed to '-ide' when present as an anion in a binary compound (e.g., chloride, oxide).
• Polyatomic ions have specific names that need to be memorized, such as sulfate (SO4^2-) or ammonium (NH4⁺).

By following these conventions, the chemical formula can be written and understood universally, facilitating collaboration and research across the globe.