Question

Consider the following equation: $$ 2 \mathrm{NO}_{2}(g) \longrightarrow \mathrm{N}_{2} \mathrm{O}_{4}(g) $$ Draw a molecular-level diagram that shows the reactants and the products for this reaction.

Short answer

The reactants are two separate NO₂ molecules. Each molecule is represented with one nitrogen atom (sphere) connected by double bonds to an oxygen atom (ellipse). The product is a single N₂O₄ molecule. The molecule is represented with two nitrogen atoms (spheres) in the center each doubly bonded to one oxygen atom (ellipse) and singly bonded to the other oxygen atom, with a single bond connecting the two nitrogen atoms.

Step-by-step solution

Understanding the Molecules

First, it is important to understand how the molecules - Nitrogen Dioxide (NO₂) and Dinitrogen Tetroxide (N₂O₄) - are structured. Each nitrogen (N) atom shares a covalent bond with an oxygen (O) atom to form Nitrogen Dioxide (NO₂). In Dinitrogen Tetroxide (N₂O₄), two molecules of Nitrogen Dioxide (NO₂) share covalent bonds. So the basic structure has two nitrogen atoms at the centre each bonded by a double bond to an oxygen atom. The two nitrogen atoms are also connected to each other.

Drawing the Reactants

To draw the reactants, make two separate molecules of Nitrogen Dioxide (NO₂). For each molecule of NO₂, represent Nitrogen (N) with a spherical shape and Oxygen (O) with elliptical shapes. The nitrogen atom should be connected with a double bond to each oxygen atom.

Drawing the Product

To draw the product Dinitrogen Tetroxide (N₂O₄), similar to the reactants, represent Nitrogen (N) with two spherical shapes and Oxygen (O) with four elliptical shapes. The nitrogen atoms should be in the center bounded doubly to one oxygen atom and singly to the other oxygen atom. The two nitrogen atoms should also be connected to each other.

Key concepts

Chemical Reaction Representation

Understanding the chemical reactions through visual representation is crucial for comprehending the transformation of substances. By visualizing molecules and their interactions, we gain insight into the process of a chemical reaction. In the case of nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4), we represent the reaction with the balanced chemical equation:
\(2 \text{NO}_2(g) \rightarrow \text{N}_2\text{O}_4(g)\). This equation tells us that two moles of nitrogen dioxide gas react to form one mole of dinitrogen tetroxide gas. By drawing diagrams of the molecules involved, we can illustrate how NO2 molecules come together and rearrange their bonds to form N2O4. This visual aid offers a clearer picture of the conversion from reactants to product, which otherwise might not be as obvious through the equation alone.

Molecular Structure Visualization

Molecular structure visualization is an essential tool for understanding the specific ways in which atoms are bonded in molecules. The proper visualization of NO2 and N2O4 involves recognizing the individual bonds and arrangement of atoms in three-dimensional space. Nitrogen and oxygen atoms can be represented by different shapes or colors to distinguish between them in diagrams. Double lines between atoms indicate a double bond, which is stronger and shorter than a single bond, depicted by a single line. These visual cues in a molecular-level diagram help us understand the connectivity and geometry of the molecule, making it easier to grasp how a chemical reaction, such as the one between NO2 and N2O4, takes place.

Nitrogen Dioxide (NO2)

Nitrogen dioxide (NO2) is a reddish-brown gas that is a significant atmospheric pollutant and plays a role in the formation of smog and acid rain. Its molecular structure consists of one nitrogen atom bonded to two oxygen atoms. An important characteristic is that one of the nitrogen-oxygen bonds is a double bond, while the other oxygen is attached by a single bond plus a lone electron on the nitrogen, making it a radical. This unpaired electron contributes to NO2's high reactivity. In molecular-level diagrams, NO2 is often represented with the nitrogen atom at the center, a double-bonded oxygen atom on one side, and a single-bonded oxygen atom with an additional electron represented on the other side.

Dinitrogen Tetroxide (N2O4)

Dinitrogen tetroxide (N2O4) exists as a colorless solid or gas and forms from the dimerization of nitrogen dioxide. This molecule's structure is more complex, with two nitrogen atoms bonded to each other and each nitrogen atom connected to two oxygen atoms. What's distinct about N2O4 is that it forms a planar structure, and often in visual diagrams, the molecule is shown with the two nitrogen atoms in the center with a single bond between them. Each nitrogen is double-bonded to one oxygen and single-bonded to another oxygen, forming a symmetrical structure. The dimerization of NO2 to N2O4 is temperature-dependent; at higher temperatures, the equilibrium shifts to favor more NO2. This transformation is reversible, making it an excellent example of dynamic equilibrium in chemical systems.