Question

Order the following molecules from lowest to highest oxidation state of the nitrogen atom: \(\mathrm{HNO}_{3}, \mathrm{NH}_{4} \mathrm{Cl}, \mathrm{N}_{2} \mathrm{O}, \mathrm{NO}_{2}\), \(\mathrm{NaNO}_{2}\).

Short answer

The molecules ordered from lowest to highest oxidation state of the nitrogen atom are: \(\mathrm{NH}_{4} \mathrm{Cl}\) (-3) < \(\mathrm{N}_{2} \mathrm{O}\) (+1) < \(\mathrm{NaNO}_{2}\) (+3) < \(\mathrm{NO}_{2}\) (+4) < \(\mathrm{HNO}_{3}\) (+5).

Step-by-step solution

Find oxidation state of nitrogen in \(\mathrm{HNO}_{3}\)

In \(\mathrm{HNO}_{3}\), the oxidation state of hydrogen is +1 and that of oxygen is -2. Let the oxidation state of nitrogen be x. Using the oxidation state equation: x + 1 + (-2) × 3 = 0 Solving for x gives: x = 5 So, the oxidation state of nitrogen in \(\mathrm{HNO}_{3}\) is +5.

Find oxidation state of nitrogen in \(\mathrm{NH}_{4} \mathrm{Cl}\)

In \(\mathrm{NH}_{4}\mathrm{Cl}\), the oxidation state of nitrogen is the same as in \(\mathrm{NH}_{4}^{+}\). The oxidation state of hydrogen is +1. Let the oxidation state of nitrogen be x. Using the oxidation state equation for \(\mathrm{NH}_{4}^{+}\): x + (4 × 1) = +1 Solving for x gives: x = -3 So, the oxidation state of nitrogen in \(\mathrm{NH}_{4} \mathrm{Cl}\) is -3.

Find oxidation state of nitrogen in \(\mathrm{N}_{2} \mathrm{O}\)

In \(\mathrm{N}_{2}\mathrm{O}\), the oxidation state of oxygen is -2. Let the oxidation state of nitrogen be x. Using the oxidation state equation: 2x + (-2) = 0 Solving for x gives: x = 1 So, the oxidation state of nitrogen in \(\mathrm{N}_{2} \mathrm{O}\) is +1.

Find oxidation state of nitrogen in \(\mathrm{NO}_{2}\)

In \(\mathrm{NO}_{2}\), the oxidation state of oxygen is -2. Let the oxidation state of nitrogen be x. Using the oxidation state equation: x + 2 × (-2) = 0 Solving for x gives: x = 4 So, the oxidation state of nitrogen in \(\mathrm{NO}_{2}\) is +4.

Find oxidation state of nitrogen in \(\mathrm{NaNO}_{2}\)

In \(\mathrm{NaNO}_{2}\), the oxidation state of sodium is +1 and that of oxygen is -2. Let the oxidation state of nitrogen be x. Using the oxidation state equation: 1 + x + 2 × (-2) = 0 Solving for x gives: x = 3 So, the oxidation state of nitrogen in \(\mathrm{NaNO}_{2}\) is +3.

Arrange the molecules in order

Now that we have the oxidation states of nitrogen in each molecule, we can arrange them in order from lowest to highest: \(\mathrm{NH}_{4} \mathrm{Cl}\) (-3) < \(\mathrm{N}_{2} \mathrm{O}\) (+1) < \(\mathrm{NaNO}_{2}\) (+3) < \(\mathrm{NO}_{2}\) (+4) < \(\mathrm{HNO}_{3}\) (+5)

Key concepts

Redox Chemistry

Redox chemistry is a fundamental aspect of chemical reactions that involve the transfer of electrons between two species. It's a shorthand for reduction-oxidation processes, where reduction pertains to the gain of electrons and oxidation involves the loss of electrons. In these reactions, one species is oxidized by losing electrons while the other is reduced by gaining those electrons.

Understanding redox chemistry is essential for a variety of applications, ranging from biochemistry to industrial processes like battery technology and metal extraction. In the educational context of the exercise, identifying the changes in oxidation states helps us understand the electron transfer during chemical reactions.

Oxidation Number Calculation

The oxidation number or oxidation state is a concept that provides a way to keep track of electrons in atoms during chemical reactions. It's a theoretical charge that an atom would have if the compound was composed entirely of ions. Calculating oxidation states involves some simple rules: atoms in their elemental form have an oxidation number of 0, the sum of oxidation numbers in a neutral compound must be 0, and in ions, it must equal the charge of the ion. Known oxidation states for common elements such as hydrogen (+1) and oxygen (-2) are used as starting points for the calculation.

For example, in the textbook exercise, by recognizing these conventions, students can calculate the oxidation states of nitrogen in various compounds, which is key in understanding their redox behavior.

Chemical Nomenclature

Chemical nomenclature is the system used for naming chemical compounds. It's not just about giving names; it's also a way to convey information about the structure and chemistry of a molecule. In nomenclature, each part of a compound's name gives insight into its components and bonding.

For instance, in the compound NaNO2, 'Na' indicates the presence of the sodium ion, and 'NO2' indicates a nitrite ion where the nitrogen is bonded to two oxygen atoms. The nomenclature becomes even more informative when paired with knowledge of oxidation states, as it allows students to deduce which form of nitrogen (e.g., nitrate vs. nitrite) is present in a compound.

Balancing Redox Equations

Balancing redox equations is a process that ensures the conservation of mass and charge in chemical reactions. Essentially, what goes into a reaction must come out, both in terms of atoms and charge. A balanced redox reaction reflects the reality that electrons lost equal electrons gained.

In the process of balancing equations, the number of atoms of each element and the overall charge must be the same on both sides of the reaction equation. Students often use the half-reaction method to balance redox reactions, which involves separately balancing the reduction and oxidation reactions and then combining them. Mastery of this skill is crucial for solving many chemical problems and is an excellent example of the application of oxidation number calculations.