Ethene (C₂H₄) reacts with halogens (X₂) by the following reaction:
C₂H₄(𝑔) + X₂(𝑔) ⇌ C₂H₄X₂(𝑔)
The following figures represent the concentrations at equilibrium at the same temperature when X₂ is Cl₂ (green), Br₂ (brown), and I₂ (purple). List the equilibria from smallest to largest equilibrium constant. [Section 15.3]

Verified step by step guidance

1. Step 1: Understand that the equilibrium constant (K) for a reaction is the ratio of the concentrations of the products to the reactants, each raised to the power of their stoichiometric coefficients in the balanced chemical equation. In this case, K = [C₂H₄X₂]/([C₂H₄][X₂]).
2. Step 2: Note that the problem does not provide numerical values for the concentrations, but we can still compare the equilibrium constants qualitatively. The larger the concentration of the product (C₂H₄X₂) at equilibrium, the larger the value of K.
3. Step 3: From the given information, we know that the colors green, brown, and purple correspond to Cl₂, Br₂, and I₂, respectively. We need to compare the concentrations of C₂H₄X₂ at equilibrium for these three halogens.
4. Step 4: The problem does not provide the actual figures, but you would need to look at the figures and determine which color (representing a specific halogen) results in the highest concentration of C₂H₄X₂ at equilibrium. The halogen that results in the highest concentration of C₂H₄X₂ will have the largest equilibrium constant.
5. Step 5: Once you have determined the order of the halogens based on the concentrations of C₂H₄X₂ at equilibrium, you can list the equilibria from smallest to largest equilibrium constant.

Key Concepts

Equilibrium Constant (K)

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. It indicates the extent to which a reaction proceeds; a larger K value suggests a greater concentration of products compared to reactants, while a smaller K indicates the opposite. Understanding K is essential for comparing the equilibria of different reactions.

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will adjust to counteract the change and restore a new equilibrium. This principle helps predict how changes in concentration, pressure, or temperature will affect the position of equilibrium, which is crucial when analyzing reactions involving different halogens in the given question.

Halogen Reactivity

Halogen reactivity refers to the tendency of halogens (like Cl₂, Br₂, and I₂) to react with other substances, which decreases down the group in the periodic table. Chlorine is more reactive than bromine, which is more reactive than iodine. This trend in reactivity influences the rate of reaction and the equilibrium constant for the reaction with ethene, affecting the comparison of their equilibrium constants.