Question

Determine the oxidation number for the indicated element in each of the following compounds:(a) Co in LiCoO \(_{2}\), (b) Al in NaAlH\(_{4}\) (c) \(\mathrm{C}\) in \(\mathrm{CH}_{3} \mathrm{OH}\) (methanol), (d) \(\mathrm{N}\) in GaN, (e) Cl in \(\mathrm{HClO}_{2},\) (f) \(\mathrm{Cr}\) in \(\mathrm{BaCrO}_{4}\).

Short answer

The oxidation numbers for the indicated elements in the given compounds are: (a) Co in LiCoO\(_{2}\) is +3, (b) Al in NaAlH\(_{4}\) is +3, (c) C in CH\(_{3}\)OH (methanol) is -2, (d) N in GaN is -3, (e) Cl in HClO\(_{2}\) is +3, and (f) Cr in BaCrO\(_{4}\) is +6.

Step-by-step solution

(a) Determining oxidation number of Co in LiCoO\(_{2}\)

In LiCoO\(_{2}\), we know that the oxidation number of Li is +1 and that of O is -2. As we know that the sum of oxidation numbers of all elements in a compound should be 0, we can determine the oxidation number of Co: Let the oxidation number of Co be x. +1 + x + 3(-2) = 0 x = +3 So, the oxidation number of Co in LiCoO\(_{2}\) is +3.

(b) Determining oxidation number of Al in NaAlH\(_{4}\)

In NaAlH\(_{4}\), we know that the oxidation number of Na is +1 and that of H is -1 (since it is bonded to a metal). We can determine the oxidation number of Al: Let the oxidation number of Al be x. +1 + x + 4(-1) = 0 x = +3 So, the oxidation number of Al in NaAlH\(_{4}\) is +3.

(c) Determining oxidation number of C in CH\(_{3}\)OH (methanol)

In methanol (CH\(_{3}\)OH), we know that the oxidation number of H is +1 and that of O is -2. We can determine the oxidation number of C: Let the oxidation number of C be x. x + 3(+1) - 2 + 1 = 0 x = -2 So, the oxidation number of C in CH\(_{3}\)OH is -2.

(d) Determining oxidation number of N in GaN

In GaN, we know that the oxidation number of Ga is +3 (since it is in group 13 of the periodic table). We can determine the oxidation number of N: Let the oxidation number of N be x. +3 + x = 0 x = -3 So, the oxidation number of N in GaN is -3.

(e) Determining oxidation number of Cl in HClO\(_{2}\)

In HClO\(_{2}\), we know that the oxidation number of H is +1 and that of O is -2. We can determine the oxidation number of Cl: Let the oxidation number of Cl be x. +1 + x + 2(-2) = 0 x = +3 So, the oxidation number of Cl in HClO\(_{2}\) is +3.

(f) Determining oxidation number of Cr in BaCrO\(_{4}\)

In BaCrO\(_{4}\), we know that the oxidation number of Ba is +2 and that of O is -2. We can determine the oxidation number of Cr: Let the oxidation number of Cr be x. +2 + x + 4(-2) = 0 x = +6 So, the oxidation number of Cr in BaCrO\(_{4}\) is +6.

Key concepts

Redox Chemistry

Redox chemistry, also known as oxidation-reduction chemistry, is a fundamental concept of chemistry involving the transfer of electrons between substances. It's a two-part process: oxidation, where an atom or molecule loses electrons, and reduction, where it gains electrons. The substance that loses electrons is said to be oxidized, while the substance that gains electrons is reduced. These reactions are essential to many natural and technological processes, such as cellular respiration, photosynthesis, and battery operations.

In a redox reaction, the total number of electrons lost is always equal to the number of electrons gained, maintaining the charge balance. This balance is crucial in determining the oxidation state of elements in chemical compounds, as seen in the provided textbook exercises.

Oxidation State Determination

The oxidation state, or oxidation number, is a concept in chemistry used to describe the degree of oxidation of an atom within a chemical compound. Determining the oxidation state of an element is a step-by-step process that depends on a set of rules. These rules include knowing the typical oxidation states of different elements - for example, hydrogen usually has an oxidation state of +1, oxygen typically has an oxidation state of -2, and alkali metals in compounds are often +1.

When determining oxidation states, it is important to know that the total oxidation state of a neutral compound is zero, and for polyatomic ions, it's equal to the charge of the ion. By using these rules, as in the provided steps for each compound in the exercise, students can correctly assign oxidation states. This process is essential for understanding redox reactions and many other chemical processes.

Chemical Compounds

Chemical compounds are substances composed of two or more different types of atoms that are chemically bonded together. The properties of a compound are distinct from those of its constituent elements. In chemistry, understanding the composition and structure of compounds helps predict their behavior and interaction with other substances.

A key aspect of compounds is how atoms are oxidized or reduced within them. Each element in a compound has its own oxidation number, which helps in assessing the result of redox reactions. As seen in the workbook solutions, complex compounds like NaAlH₄ or BaCrO₄ have distinct oxidation states that contribute to their chemical properties and reactions they undergo. Understanding the distribution of oxidation states among the atoms of a compound is crucial for a comprehensive grasp of chemical reactions and bonding.