When 0.500 mol of N2O4 is placed in a 4.00-L reaction vessel and heated at 400 K, 79.3% of the N2O4 decom- poses to NO2. (b) Draw an electron-dot structure for NO2, and rational- ize the structure of N2O4.

Verified step by step guidance

1. Draw the electron-dot structure for NO2: Start by counting the total number of valence electrons. Nitrogen (N) has 5 valence electrons and each oxygen (O) has 6 valence electrons. Therefore, NO2 has a total of 5 + 2(6) = 17 valence electrons.
2. Place the nitrogen atom in the center and connect it to each oxygen atom with a single bond. This uses 4 electrons (2 for each bond), leaving 13 electrons to distribute.
3. Distribute the remaining electrons to satisfy the octet rule for the oxygen atoms first. Place 6 electrons (3 pairs) around each oxygen atom, using up 12 electrons, leaving 1 electron.
4. Place the remaining electron on the nitrogen atom. This results in a structure where nitrogen has 5 electrons around it, indicating that NO2 is a radical species.
5. Rationalize the structure of N2O4: N2O4 can be considered as two NO2 units connected by a single bond. Each NO2 unit has a nitrogen atom double-bonded to one oxygen and single-bonded to another oxygen, with the unpaired electron from each NO2 forming a bond between the two units, resulting in a stable N2O4 molecule.

Key Concepts

Molecular Structure and Electron-Dot Diagrams

Electron-dot diagrams, or Lewis structures, represent the valence electrons of atoms within a molecule. They help visualize how atoms bond and the arrangement of electrons, which is crucial for understanding molecular geometry and reactivity. For NO2, the structure shows the arrangement of nitrogen and oxygen atoms, including the presence of lone pairs and double bonds.

Decomposition Reactions

A decomposition reaction occurs when a single compound breaks down into two or more simpler products. In this case, N2O4 decomposes into NO2. Understanding the stoichiometry of the reaction is essential for calculating the amounts of reactants and products involved, especially when given a percentage of decomposition.

Equilibrium and Reaction Conditions

The conditions under which a reaction occurs, such as temperature and concentration, can significantly affect the extent of the reaction. In this scenario, heating N2O4 at 400 K influences its decomposition to NO2. Recognizing how temperature impacts reaction rates and equilibrium helps in predicting the behavior of the system and the final concentrations of the products.