The reaction SO₂(g) + 2 H₂S(g) ⇌ 3 S(s) + 2 H₂O(g) is the basis of a suggested method for removal of SO₂ from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (d) Would you expect the process to be more or less effective at higher temperatures?

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Identify the reaction: SO_2(g) + 2 H_2S(g) ⇌ 3 S(s) + 2 H_2O(g).

Determine the standard free energy change (ΔG°) for the reaction using the formula: ΔG° = ΣΔG°(products) - ΣΔG°(reactants).

Consider the effect of temperature on the reaction's spontaneity. If ΔG° is negative, the reaction is spontaneous at standard conditions. If positive, it is non-spontaneous.

Apply the Gibbs free energy equation: ΔG = ΔH - TΔS, where ΔH is the enthalpy change and ΔS is the entropy change. Analyze how increasing temperature (T) affects ΔG.

Conclude whether the reaction becomes more or less spontaneous at higher temperatures based on the signs of ΔH and ΔS.

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Key Concepts

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

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 temperature changes, if the reaction is exothermic, increasing the temperature will shift the equilibrium to favor the reactants, while decreasing the temperature will favor the products.

Gibbs Free Energy

Gibbs Free Energy (G) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. The change in Gibbs Free Energy (ΔG) during a reaction indicates whether the process is spontaneous; a negative ΔG suggests that the reaction can occur spontaneously, while a positive ΔG indicates non-spontaneity.

Endothermic vs. Exothermic Reactions

Reactions can be classified as endothermic or exothermic based on their heat exchange with the surroundings. Exothermic reactions release heat, leading to an increase in temperature, while endothermic reactions absorb heat, resulting in a decrease in temperature. Understanding the nature of the reaction in question is crucial for predicting how temperature changes will affect the equilibrium position.

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Endothermic & Exothermic Reactions

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Textbook Question

Consider the following equilibrium: N₂O₄(g) ⇌ 2 NO₂(g) Thermodynamic data on these gases are given in Appendix C. You may assume that ΔH° and ΔS° do not vary with temperature. (a) At what temperature will an equilibrium mixture contain equal amounts of the two gases?

Textbook Question

The reaction SO₂(g) + 2 H₂S(g) ⇌ 3 S(s) + 2 H₂O(g) is the basis of a suggested method for removal of SO2 from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (a) What is the equilibrium constant for the reaction at 298 K? (c) If P_SO2 = P_H2S and the vapor pressure of water is 25 torr, calculate the equilibrium SO₂ pressure in the system at 298 K.

Textbook Question

The reaction SO₂(g) + 2 H₂S(g) ⇌ 3 S(s) + 2 H₂O(g) is the basis of a suggested method for removal of SO₂ from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (b) In principle, is this reaction a feasible method of removing SO₂?

Textbook Question

When most elastomeric polymers (e.g., a rubber band) are stretched, the molecules become more ordered, as illustrated here:

Suppose you stretch a rubber band. (a) Do you expect the entropy of the system to increase or decrease?

The reaction SO2(g) + 2 H2S(g) ⇌ 3 S(s) + 2 H2O(g) is the basis of a suggested method for removal of SO2 from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (d) Would you expect the process to be more or less effective at higher temperatures?

Verified video answer for a similar problem:

Key Concepts

Le Chatelier's Principle

Gibbs Free Energy

Endothermic vs. Exothermic Reactions

The reaction SO₂(g) + 2 H₂S(g) ⇌ 3 S(s) + 2 H₂O(g) is the basis of a suggested method for removal of SO₂ from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (d) Would you expect the process to be more or less effective at higher temperatures?