Ethene (C₂H₄) can be halogenated by this reaction: C₂H₄(g) + X₂(g) ⇌ C₂H₄X₂(g) where X₂ can be Cl₂ (green), Br₂ (brown), or I₂ (purple). Examine the three figures representing equilibrium concentrations in this reaction at the same temperature for the three different hal- ogens. Rank the equilibrium constants for the three reactions from largest to smallest.

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Identify the species in each diagram: A (red) represents C2H4, B (green) represents X2, and C (blue), D (orange), E (gray) represent C2H4X2 for Cl2, Br2, and I2 respectively.

Count the number of each species in each diagram to determine the equilibrium concentrations.

Calculate the equilibrium constant (K) for each reaction using the formula K = [C2H4X2] / ([C2H4] * [X2]).

Compare the calculated equilibrium constants for the three reactions.

Rank the equilibrium constants from largest to smallest based on the calculated values.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. A larger K value indicates a greater concentration of products compared to reactants, suggesting that the reaction favors product formation. In the context of halogenation of ethene, comparing K values for Cl2, Br2, and I2 will reveal which halogen leads to a more favorable reaction.

Halogen Reactivity

Halogens vary in their reactivity, which influences the rate and extent of reactions with alkenes like ethene. Chlorine (Cl2) is generally more reactive than bromine (Br2), which in turn is more reactive than iodine (I2). This trend affects the equilibrium position of the halogenation reaction, with more reactive halogens typically leading to higher equilibrium constants.

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. In the context of the halogenation of ethene, if the concentration of one of the halogens is increased, the equilibrium will shift to favor the formation of products, thereby affecting the equilibrium constant and the concentrations of the reactants and products.

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Le Chatelier's Principle

Related Practice

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Find and fix each mistake in the equilibrium constant expressions. a. 2 H₂S(g) ⇌ 2 H₂(g) + S₂(g) K = [H₂][S₂]/[H₂S]

Textbook Question

Find and fix each mistake in the equilibrium constant expressions. b. CO(g) + Cl₂(g) ⇌ COCl₂(g) K = [CO][Cl₂]/[COCl₂]

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When this reaction comes to equilibrium, will the concentrations of the reactants or products be greater? Does the answer to this question depend on the initial concentrations of the reactants and products? A(g)+B(g) ⇌ 2 C(g) K_c = 1.4⨉10^-5

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H₂ and I₂ are combined in a flask and allowed to react according to the reaction: H₂(g) + I₂(g) ⇌ 2 HI(g) Examine the figures (sequential in time) and answer the questions: a. Which figure represents the point at which equilibrium is reached?

Textbook Question

A chemist trying to synthesize a particular compound attempts two different synthesis reactions. The equilibrium constants for the two reactions are 23.3 and 2.2⨉10⁴ at room temperature. However, upon carrying out both reactions for 15 minutes, the chemist finds that the reaction with the smaller equilibrium constant produces more of the desired product. Explain how this might be possible.

Textbook Question

This reaction has an equilibrium constant of K_p = 2.26⨉10⁴ at 298 K. CO(g) + 2 H₂(g) ⇌ CH₃OH(g) Calculate K_p for each reaction and predict whether reactants or products will be favored at equilibrium. a. CH₃OH(g) ⇌ CO(g) + 2 H₂(g)