Question

What is the oxidation number of carbon in \(\mathrm{C}_{3} \mathrm{O}_{2}\) (carbon suboxide)? (a) \(+4 / 3\) (b) \(+10 / 4\) (c) \(+2\) (d) \(+2 / 3\)

Short answer

The oxidation number of carbon in \(\mathrm{C}_{3}O_{2}\) is \(+4 / 3\).

Step-by-step solution

Determine the oxidation number of oxygen

First, it is important to know that the oxidation number of oxygen in compounds is usually -2. Since there are 2 oxygen atoms in \(\mathrm{C}_{3}O_{2}\), the total oxidation number for the oxygen atoms is \(2 \times -2 = -4\).

Set up the equation for the total oxidation state of the compound

The sum of the oxidation numbers in a neutral compound must equal 0. We set up the equation \(3 \times \text{OX}_{\text{C}} + (-4) = 0\) where \(\text{OX}_{\text{C}}\) is the oxidation number of carbon we are trying to find.

Solve for the oxidation number of carbon

Isolate \(\text{OX}_{\text{C}}\) in the equation: \(3 \times \text{OX}_{\text{C}} = 4\). Divide both sides by 3 to find the oxidation number of carbon: \(\text{OX}_{\text{C}} = 4 / 3\) which simplifies to \(\text{OX}_{\text{C}} = +4 / 3\).

Key concepts

Redox Chemistry

Redox chemistry is a fundamental concept in chemistry involving the transfer of electrons between two substances. It's a shorthand for 'reduction-oxidation' chemistry. Reduction refers to the gain of electrons by a molecule, atom, or ion, while oxidation is the loss of electrons. Importantly, in any redox reaction, one species is oxidized (loses electrons) and another is reduced (gains electrons).

To understand redox reactions, one must look at the oxidation numbers of the atoms involved. This not only helps in identifying which atoms are getting oxidized and which are getting reduced, but also in balancing redox equations. The change in oxidation numbers indicates the number of electrons transferred in the reaction. In redox chemistry, these electrons do not exist freely, but are transferred from one species to another, contributing to chemical bonding.

Chemical Bonding

Chemical bonding is the physical phenomenon that enables atoms to come together and stay together in molecules and compounds. The bonds form due to the attraction between the charged particles—protons and electrons—and the repulsion between like charges on electron shells. There are several types of chemical bonds, including ionic, covalent, hydrogen bonds, and metallic bonds. Each bond type involves electrons in different ways.

In the context of redox reactions, the making and breaking of chemical bonds involve changes in the arrangement of electrons, which directly relates to oxidation numbers. For instance, when a covalent bond between two atoms is broken, one atom might take more of the shared electrons, increasing its negative charge (reduction), while the other loses electrons, becoming more positively charged (oxidation). The intricate dance of electrons is key to the structure and stability of molecules.

Oxidation States

Oxidation states, also referred to as oxidation numbers, are a bookkeeping tool used in chemistry to keep track of electron distribution in molecules and ions. The oxidation state is a hypothetical charge that an atom would have if all bonds to atoms of different elements were completely ionic. It is a way of summing up the results of all possible redox processes involving that atom.

Oxidation numbers are vital in determining the products of redox reactions and in writing and balancing chemical equations. A few guidelines can help when assigning oxidation states: Oxygen usually has an oxidation state of -2, hydrogen +1 when paired with nonmetals, and metals can have positive oxidation states reflecting their usual cationic forms. In the provided example, by assigning oxygen with an oxidation state of -2, it becomes possible to calculate the oxidation state of carbon in \(\mathrm{C}_{3} \mathrm{O}_{2}\) as +4/3, indicating that each carbon atom has lost some degree of electron density overall, even though carbon typically forms covalent bonds.