Problem 31 - Chemistry: An Atoms-Focused Approach

Question

What are the names of the cobalt oxides that have the following formulas? (a) \(\operatorname{Co} \mathrm{O} ;\) (b) \(\mathrm{Co}_{2} \mathrm{O}_{3} ;\) (c) \(\mathrm{CoO}_{2}.\)

Step-by-Step Solution

Answer

Question: Name the cobalt oxides with the formulas CoO, Co2O3, and CoO2. Answer: The cobalt oxides are named as follows: CoO is Cobalt (II) Oxide, Co2O3 is Cobalt (III) Oxide, and CoO2 is Cobalt (IV) Oxide.

Step 1: Identify the oxidation numbers of the cobalt in the compounds

To name the cobalt oxides, we need to first determine the oxidation number of Cobalt in each compound. Since oxygen has an oxidation number of -2, we can calculate the oxidation number of cobalt in each compound.

Step 2: Naming Cobalt (II) Oxide (CoO)

CoO has an oxidation number of +2 for cobalt, since there is one oxygen atom with an oxidation state of -2. Therefore, the cobalt oxide with the formula CoO is called Cobalt (II) Oxide.

Step 3: Naming Cobalt (III) Oxide (Co2O3)

Co2O3 has two cobalt atoms, and three oxygen atoms with an oxidation state of -2. Thus, the cobalt's oxidation number is +3 (since 2(+3) + 3(-2) = 0). Therefore, the cobalt oxide with the formula Co2O3 is called Cobalt (III) Oxide.

Step 4: Naming Cobalt (IV) Oxide (CoO2)

CoO2 has one cobalt atom, and two oxygen atoms with an oxidation state of -2. Thus, the cobalt's oxidation number is +4 (since (+4) + 2(-2) = 0). Therefore, the cobalt oxide with the formula CoO2 is called Cobalt (IV) Oxide.

Key Concepts

Cobalt Oxides

Cobalt oxides are compounds that combine the element cobalt with oxygen. These compounds are notable because cobalt can exist in various oxidation states, resulting in different chemical formulas and properties. Cobalt oxides are important in industrial processes and as pigments in ceramics. Some common examples include:

• Cobalt(II) Oxide, CoO: It appears as an olive-green to red solid, used in creating blue pigments for glass and ceramics.
• Cobalt(III) Oxide, Co₂O₃: A black crystalline compound, typically used in the manufacture of batteries and catalysts.
• Cobalt(IV) Oxide, CoO₂: Rarely found in pure form, it is often used in lithium-cobalt batteries.

Each type of oxide has different stability and application, primarily depending on the oxidation state of the cobalt atom.

Oxidation Numbers

Oxidation numbers are used to indicate the degree of oxidation of an element in a chemical compound. They are critical in naming chemical compounds, particularly those involving transition metals like cobalt.
When determining the oxidation number, remember that oxygen usually has an oxidation state of -2. By knowing this, we can deduce the oxidation numbers of other elements within compounds. For example:

• In CoO, with one oxygen (-2), the single cobalt must be +2.
• In Co₂O₃, three oxygens add to -6. To balance this, each of the two cobalt atoms takes on an oxidation number of +3.
• In CoO₂, two oxygens equal -4, making the cobalt's oxidation number +4 to maintain charge neutrality.

This step is vital for the correct naming and understanding of how elements interact within a compound.

Transition Metals

Transition metals, such as cobalt, are elements found in the d-block of the periodic table. They are known for their ability to exist in multiple oxidation states, which contributes to their versatility in forming a variety of compounds.
These metals exhibit characteristics like high melting points, the ability to form colored compounds, and splendid catalyst properties. One of the complexities they introduce into chemistry is their naming, due to variable oxidation numbers that require precise identification.
When working with transition metals, it is especially important to identify oxidation states because they directly affect the chemical nomenclature and reactivity of the compounds. Mastery of these concepts is crucial for anyone studying chemistry.

Chemical Nomenclature

Chemical nomenclature refers to the systematic method of naming chemical substances, structured to convey important information about the compound's makeup and properties.
Within the realm of transition metals, the names often include Roman numerals to show the oxidation state of the metal. This notation helps avoid confusion as many transition metals can form differently charged ions.

• Cobalt(II) Oxide: Indicates Cobalt in oxidation state +2.
• Cobalt(III) Oxide: Indicates Cobalt in oxidation state +3.
• Cobalt(IV) Oxide: Indicates Cobalt in oxidation state +4.

By using these conventions, scientists ensure that the names accurately reflect the chemical formula, aiding in both written communication and verbal discussions within the scientific community.