Gibbs Free Energy Video Lessons

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# Problem: The reactionSO2(g)+2H2S(g) ⇌ 3 S(s)+2H2O(g)is the basis of a suggested method for removal of SO2, a pollutant that irritates airways causing coughing, from power-plant stack gases.The values below may be helpful when answering questions about the process.   Substance      ΔG∘f(kJ/mol)      ΔH∘f(kJ/mol)      H2O(g)  −228.6  −241.8   H2O(l)  −237.1  −285.8   SO2(g)  −300.4  −296.9   SO3(g)  −370.4  −395.2   H2S(g)  −33.01  −20.17   S(s)  0  0PART A:Calculate the equilibrium constant Kp for the reaction at a temperature of 298 K.Express the equilibrium constant to one significant figure.PART B:In principle, is this reaction a feasible method of removing SO2 from power-plant emissions?a) No; the reaction is highly spontaneous at 298 K, but a significant amount of SO2 will remain at equilibrium.b) Yes; the reaction is highly spontaneous at 298 K, even though a significant amount of SO2will remain at equilibrium.c) Yes; the reaction is highly spontaneous at 298 K and almost no SO2 will remain at equilibrium.d) No; the reaction is not spontaneous at 298 K, even though almost no SO2 will remain at equilibrium.e) No; the reaction is not spontaneous at 298 K and a significant amount of SO2 will remain at equilibrium.PART C:Assume that the partial pressure of sulfur dioxide, PSO2, is equal to the partial pressure of dihydrogen sulfide, PH2S, and therefore PSO2=PH2S. If the vapor pressure of water is 28 torr , calculate the equilibrium partial pressure of SO2  (PSO2) in the system at 298 K. Express the pressure in atmospheres to two significant figures.PART DUsing Le Châtelier's principle, determine how the process is affected after each of the following temperature or pressure changes. Consider that a more effective reaction produces more product or more product in a shorter amount of time.Drag the appropriate items to their respective categories: More effective, Less effective, Equally effective-Pressure decreases by increasing the container size.-Pressure increases by decreasing the container size.-Temperature increases while maintaining the container size.-Temperature decreases while maintaining the container size.

###### FREE Expert Solution

Part A: To calculate Kp for the reaction:

$\overline{){\mathbf{\Delta G}}{{\mathbf{°}}}_{{\mathbf{rxn}}}{\mathbf{=}}{\mathbf{-}}{\mathbf{RTlnK}}}$

$\overline{){\mathbf{\Delta G}}{{\mathbf{°}}}_{{\mathbf{rxn}}}{\mathbf{=}}{{\mathbf{\Delta G}}}_{{\mathbf{f}}}{{\mathbf{°}}}_{{\mathbf{products}}}{\mathbf{-}}{{\mathbf{\Delta G}}}_{{\mathbf{f}}}{{\mathbf{°}}}_{{\mathbf{reactants}}}}$

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###### Problem Details

The reaction

SO2(g)+2H2S(g) ⇌ 3 S(s)+2H2O(g)

is the basis of a suggested method for removal of SO2, a pollutant that irritates airways causing coughing, from power-plant stack gases.

 Substance ΔG∘f(kJ/mol) ΔH∘f(kJ/mol) H2O(g) −228.6 −241.8 H2O(l) −237.1 −285.8 SO2(g) −300.4 −296.9 SO3(g) −370.4 −395.2 H2S(g) −33.01 −20.17 S(s) 0 0

PART A:

Calculate the equilibrium constant Kp for the reaction at a temperature of 298 K.

Express the equilibrium constant to one significant figure.

PART B:

In principle, is this reaction a feasible method of removing SO2 from power-plant emissions?

a) No; the reaction is highly spontaneous at 298 K, but a significant amount of SO2 will remain at equilibrium.

b) Yes; the reaction is highly spontaneous at 298 K, even though a significant amount of SO2will remain at equilibrium.

c) Yes; the reaction is highly spontaneous at 298 K and almost no SO2 will remain at equilibrium.

d) No; the reaction is not spontaneous at 298 K, even though almost no SO2 will remain at equilibrium.

e) No; the reaction is not spontaneous at 298 K and a significant amount of SO2 will remain at equilibrium.

PART C:

Assume that the partial pressure of sulfur dioxide, PSO2, is equal to the partial pressure of dihydrogen sulfide, PH2S, and therefore PSO2=PH2S. If the vapor pressure of water is 28 torr , calculate the equilibrium partial pressure of SO2  (PSO2) in the system at 298 K. Express the pressure in atmospheres to two significant figures.

PART D

Using Le Châtelier's principle, determine how the process is affected after each of the following temperature or pressure changes. Consider that a more effective reaction produces more product or more product in a shorter amount of time.

Drag the appropriate items to their respective categories: More effective, Less effective, Equally effective

-Pressure decreases by increasing the container size.

-Pressure increases by decreasing the container size.

-Temperature increases while maintaining the container size.

-Temperature decreases while maintaining the container size.