Consider the gas-phase reaction of AB3 and A2 molecules:
(a) Write a balanced equation for the reaction. (b) What is the sign of the entropy change for the reaction?

Verified step by step guidance

1. Identify the reactants and products in the given image. The left side shows AB3 and A2 molecules, and the right side shows the products of the reaction.
2. Count the number of each type of molecule on both sides of the reaction. On the left, there are 6 AB3 molecules and 3 A2 molecules. On the right, there are 6 A2B3 molecules.
3. Write the balanced chemical equation for the reaction. Ensure that the number of atoms of each element is the same on both sides of the equation.
4. Determine the change in the number of gas molecules from reactants to products. Compare the total number of gas molecules on the reactant side with the total number on the product side.
5. Analyze the entropy change (ΔS) for the reaction. If the number of gas molecules decreases, the entropy change is negative (ΔS < 0). If the number of gas molecules increases, the entropy change is positive (ΔS > 0).

Key Concepts

Balanced Chemical Equation

A balanced chemical equation represents a chemical reaction with equal numbers of each type of atom on both sides of the equation. This ensures the law of conservation of mass is upheld, meaning that matter is neither created nor destroyed during the reaction. In this case, the reaction involves the combination of AB3 and A2, and the balanced equation will reflect the stoichiometry of the reactants and products.

Entropy Change (ΔS)

Entropy (S) is a measure of the disorder or randomness in a system. The change in entropy (ΔS) during a reaction indicates whether the disorder of the system increases or decreases. In gas-phase reactions, an increase in the number of gas molecules typically leads to a positive ΔS, while a decrease results in a negative ΔS. Understanding the molecular arrangement before and after the reaction is crucial for determining the sign of ΔS.

Molecular Representation and Reaction Dynamics

Molecular representation visually depicts the arrangement and interaction of molecules in a reaction. Analyzing these representations helps in understanding how reactants transform into products, including changes in molecular structure and the number of molecules involved. In the provided image, the arrangement of AB3 and A2 molecules can provide insights into the potential changes in entropy and the balanced equation for the reaction.