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Ch.19 - Chemical Thermodynamics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.19 - Chemical ThermodynamicsProblem 111b
Chapter 19, Problem 111b

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?

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Identify the standard free energy of formation (\( \Delta G^\circ_f \)) for each substance involved in the reaction from Appendix C.
Write the balanced chemical equation: \( \text{SO}_2(g) + 2 \text{H}_2\text{S}(g) \rightleftharpoons 3 \text{S}(s) + 2 \text{H}_2\text{O}(g) \).
Calculate the standard free energy change (\( \Delta G^\circ \)) for the reaction using the formula: \( \Delta G^\circ = \sum \Delta G^\circ_f(\text{products}) - \sum \Delta G^\circ_f(\text{reactants}) \).
Determine the sign of \( \Delta G^\circ \). If \( \Delta G^\circ < 0 \), the reaction is spontaneous under standard conditions, suggesting feasibility.
Discuss the implications of the \( \Delta G^\circ \) value in terms of the reaction's feasibility for removing \( \text{SO}_2 \) from power-plant stack gases.

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Key Concepts

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

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. A negative change in Gibbs Free Energy (ΔG) indicates that a reaction is spontaneous and can occur without external energy input. Understanding ΔG is crucial for assessing the feasibility of chemical reactions, such as the removal of SO₂ in this context.
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Gibbs Free Energy of Reactions

Equilibrium Constant

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a reversible reaction. It provides insight into the position of equilibrium and the extent to which a reaction proceeds. For the reaction in question, analyzing K can help determine whether the formation of products (S and H₂O) is favored over the reactants (SO₂ and H₂S), indicating the feasibility of SO₂ removal.
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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 is essential for understanding how changes in concentration, pressure, or temperature can affect the reaction's direction and feasibility, particularly in the context of removing SO₂ from stack gases.
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Related Practice
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 PSO2 = PH2S and the vapor pressure of water is 25 torr, calculate the equilibrium SO2 pressure in the system at 298 K.

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. (d) Would you expect the process to be more or less effective at higher temperatures?

Textbook Question
The following data compare the standard enthalpies and free energies of formation of some crystalline ionic substances and aqueous solutions of the substances:(a) Write the formation reaction for AgNO31s2. Based on this reaction, do you expect the entropy of the system to increase or decrease upon the formation of AgNO31s2? (b) Use ΔH°f and ΔG°f of AgNO31s2 to determine the entropy change upon formation of the substance. Is your answer consistent with your reasoning in part (a)?
Textbook Question
Hydrogen gas has the potential for use as a clean fuel inreaction with oxygen. The relevant reaction is2 H21g2 + O21g2 ¡ 2 H2O1l2Consider two possible ways of utilizing this reaction asan electrical energy source: (i) Hydrogen and oxygengases are combusted and used to drive a generator, muchas coal is currently used in the electric power industry;(ii) hydrogen and oxygen gases are used to generate electricity directly by using fuel cells that operate at 85 °C.(a) Use data in Appendix C to calculate ∆H° and ∆S° forthe reaction. We will assume that these values do notchange appreciably with temperature.
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?