Question

Assign oxidation numbers to each element in the following compounds: (a) \(\mathrm{NO}_{2}\) (b) \(\mathrm{SO}_{3}\) (c) \(\mathrm{COCl}_{2}\) (d) \(\mathrm{CH}_{2} \mathrm{Cl}_{2}\) (e) \(\mathrm{KClO}_{3}\) (f) \(\mathrm{HNO}_{3}\)

Short answer

NO2: N=+4, O=-2; SO3: S=+6, O=-2; COCl2: C=+4, O=-2, Cl=-1; CH2Cl2: C=0, H=+1, Cl=-1; KClO3: K=+1, Cl=+5, O=-2; HNO3: H=+1, N=+5, O=-2.

Step-by-step solution

Understanding the Rules for Assigning Oxidation Numbers

The key rules for finding oxidation numbers are: 1. The oxidation number of an atom in its elemental form is 0. 2. The oxidation number for a monoatomic ion is equal to its charge. 3. Hydrogen generally has an oxidation number of +1, and oxygen generally has an oxidation number of -2. 4. The sum of oxidation numbers in a neutral compound is 0, while in an ion, it is equal to the ion charge.

Assign Oxidation Numbers in NO2

In \(\mathrm{NO}_{2}\):- Assign the oxidation number of O as -2.- Let the oxidation number of N be x.- The equation becomes: \[x + 2(-2) = 0\]- Simplify to solve for x: \[x = +4\]- Therefore, the oxidation number for N is +4.

Assign Oxidation Numbers in SO3

In \(\mathrm{SO}_{3}\):- Assign the oxidation number of O as -2.- Let the oxidation number of S be y.- The equation becomes: \[y + 3(-2) = 0\]- Simplify to solve for y: \[y = +6\]- Therefore, the oxidation number for S is +6.

Assign Oxidation Numbers in COCl2

In \(\mathrm{COCl}_{2}\):- Assign the oxidation number of O as -2 and Cl as -1.- Let the oxidation number of C be z.- The equation becomes: \[z + (-2) + 2(-1) = 0\]- Simplify to solve for z: \[z = +4\]- Therefore, the oxidation number for C is +4.

Assign Oxidation Numbers in CH2Cl2

In \(\mathrm{CH}_{2}\mathrm{Cl}_{2}\):- Assign the oxidation number of H as +1, and Cl as -1.- Let the oxidation number of C be w.- The equation becomes: \[w + 2(+1) + 2(-1) = 0\]- Simplify to solve for w: \[w = 0\]- Therefore, the oxidation number for C is 0.

Assign Oxidation Numbers in KClO3

In \(\mathrm{KClO}_{3}\):- Assign the oxidation number of K as +1 and O as -2.- Let the oxidation number of Cl be a.- The equation becomes: \[+1 + a + 3(-2) = 0\]- Simplify to solve for a: \[a = +5\]- Therefore, the oxidation number for Cl is +5.

Assign Oxidation Numbers in HNO3

In \(\mathrm{HNO}_{3}\):- Assign the oxidation number of H as +1 and O as -2.- Let the oxidation number of N be b.- The equation becomes: \[+1 + b + 3(-2) = 0\]- Simplify to solve for b: \[b = +5\]- Therefore, the oxidation number for N is +5.

Key concepts

Redox Reactions

Redox reactions are a fundamental concept in chemistry and are crucial for understanding many natural and industrial processes. The term "redox" is short for reduction-oxidation. It involves the transfer of electrons between chemical species. In any redox reaction, one species loses electrons (oxidation) while another gains electrons (reduction). - **Oxidation**: Refers to the loss of electrons. The substance that gives away electrons is said to be oxidized, and it often involves an increase in oxidation state. For example, in the reaction of zinc with hydrochloric acid, zinc is oxidized as it loses electrons. - **Reduction**: In contrast, refers to the gaining of electrons. The substance that gains electrons is reduced, which involves a decrease in its oxidation state. Continuing with the zinc and hydrochloric acid example, the hydrogen ions gain electrons, leading to their reduction. Understanding redox reactions is critical in a variety of applications, including energy generation in batteries, digestion within living organisms, and the process of metal corrosion.

Chemical Compounds

Chemical compounds are substances composed of two or more different elements chemically bonded together. These compounds can be classified into various types, such as ionic or covalent, depending on the nature of the bonding between their elements.

• Ionic Compounds: Are formed through ionic bonds, which occur between ions of opposite charges. A classic example is sodium chloride (NaCl), where sodium donates an electron to chlorine, creating a bond between Na⁺ and Cl⁻.
• Covalent Compounds: Are formed when atoms share electrons. For instance, in water ( H₂O ), oxygen and hydrogen share electrons, leading to covalent bonding.

Chemical compounds have distinct properties and structures based on their types of bonding and constituent elements. Understanding these distinctions is essential in predicting reaction outcomes and manipulating chemical processes. When dealing with redox reactions, it's important to accurately assign oxidation numbers in chemical compounds, as it helps in identifying which species are oxidized and reduced.

Oxidation States

Oxidation states, also known as oxidation numbers, are a helpful way to keep track of electron transfers in chemical reactions. They indicate the degree of oxidation of an atom within a compound. By setting certain rules, chemists can consistently determine the oxidation state of atoms in both simple and complex molecules. Here's a quick refresher on the rules:

• Atoms in their elemental form have an oxidation state of 0 (e.g., O₂ or N₂).
• The oxidation state of a monatomic ion is equal to its charge (e.g., Na⁺ is +1).
• Oxygen typically has an oxidation number of -2, except in peroxides or bonded to fluorine.
• Hydrogen usually is +1, unless it's bonded to metals in hydrides, where it is -1.
• The sum of oxidation states in a neutral compound equals 0, while for ions, it equals the charge of the ion.

By applying these rules, we can analyze reactions and better understand the movement of electrons, helping to elucidate the redox process. This knowledge is also crucial in predicting products, balancing reactions, and understanding chemical behavior more generally.