Reactions in which a substance decomposes by losing CO are called decarbonylation reactions. The decarbonylation of acetic acid proceeds according to: $$ \mathrm{CH}_{3} \mathrm{COOH}(l) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(g)+\mathrm{CO}(g) $$ By using data from Appendix \(\mathrm{C}\) , calculate the minimum temperature at which this process will be spontaneous under standard conditions. Assume that \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) do not vary with temperature.

Short Answer

Expert verified
To find the minimum temperature at which the decarbonylation of acetic acid will be spontaneous under standard conditions, first calculate the values of enthalpy change (∆H°) and entropy change (∆S°) for the reaction using the data from Appendix C: \[ \Delta H^{\circ}_{reaction} = \sum \Delta H^{\circ}_{products} - \sum \Delta H^{\circ}_{reactants} \] \[ \Delta S^{\circ}_{reaction} = \sum \Delta S^{\circ}_{products} - \sum \Delta S^{\circ}_{reactants} \] Apply the Gibbs-Helmholtz equation and the condition for spontaneity: \[ \Delta H^{\circ} - T \Delta S^{\circ} < 0 \] Rearrange the inequality to solve for the temperature: \[ T > \frac{\Delta H^{\circ}}{\Delta S^{\circ}} \] Plug in the values for ∆H° and ∆S° and calculate the minimum temperature: \[ T > \frac{(\text{Value of } \Delta H^{\circ})}{(\text{Value of } \Delta S^{\circ})} \]

Step by step solution

01

Calculate the values of ∆H° and ∆S° for the reaction

Begin by calculating the values of enthalpy change (∆H°) and entropy change (∆S°) for the reaction using the data from Appendix C of the textbook. For each component, find the respective values and use the stoichiometry of the reaction to determine the overall values: \[ \Delta H^{\circ}_{reaction} = \sum \Delta H^{\circ}_{products} - \sum \Delta H^{\circ}_{reactants} \] \[ \Delta S^{\circ}_{reaction} = \sum \Delta S^{\circ}_{products} - \sum \Delta S^{\circ}_{reactants} \]
02

Determine the equation relating ∆G° with the minimum temperature

Use the Gibbs-Helmholtz equation as shown before: \[ \Delta G^{\circ} = \Delta H^{\circ} - T\Delta S^{\circ} \] Then, apply the condition for spontaneity: \[ \Delta G^{\circ} < 0 \] Substitute the equation for ΔG°: \[ \Delta H^{\circ} - T \Delta S^{\circ} < 0 \]
03

Solve for the minimum temperature

Rearrange the inequality to solve for the temperature: \[ T > \frac{\Delta H^{\circ}}{\Delta S^{\circ}} \] Now, plug in the values for ∆H° and ∆S° you calculated in Step 1: \[ T > \frac{(\text{Value of } \Delta H^{\circ})}{(\text{Value of } \Delta S^{\circ})} \] Calculate the value of the minimum temperature, which is the answer to this problem.

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Most popular questions from this chapter

Consider a process in which an ideal gas changes from state 1 to state 2 in such a way that its temperature changes from 300 K to 200 K. (a) Does the temperature change depend on whether the process is reversible or irreversible? (b) Is this process isothermal? (c) Does the change in the internal energy, \(\Delta E,\) depend on the particular pathway taken to carry out this change of state?

(a) Using data in Appendix \(C,\) estimate the temperature at which the free- energy change for the transformation from \(\mathrm{I}_{2}(s)\) to \(\mathrm{I}_{2}(g)\) is zero. (b) Use a reference source, such as Web Elements (www. webelements.com), to find the experimental melting and boiling points of \(I_{2}\) (c) Which of the values in part (b) is closer to the value you obtained in part (a)?

(a) What is the difference between a state and a microstate of a system? (b) As a system goes from state A to state \(B,\) its entropy decreases. What can you say about the number of microstates corresponding to each state? (c) In a particular spontaneous process, the number of microstates available to the system decreases. What can you conclude about the sign of \(\Delta S_{\text { surr }}\) ?

Using data from Appendix \(\mathrm{C}\) , calculate \(\Delta G^{\circ}\) for the following reactions. Indicate whether each reaction is spontaneous at 298 \(\mathrm{K}\) under standard conditions. $$ \begin{array}{l}{\text { (a) } 2 \mathrm{Ag}(s)+\mathrm{Cl}_{2}(g) \longrightarrow 2 \mathrm{AgCl}(s)} \\ {\text { (b) } \mathrm{P}_{4} \mathrm{O}_{10}(s)+16 \mathrm{H}_{2}(g) \longrightarrow 4 \mathrm{PH}_{3}(g)+10 \mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (c) } \mathrm{CH}_{4}(g)+4 \mathrm{F}_{2}(g) \longrightarrow \mathrm{CF}_{4}(g)+4 \mathrm{HF}(g)} \\ {\text { (d) } 2 \mathrm{H}_{2} \mathrm{O}_{2}(l) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)}\end{array} $$

The reaction $$ \mathrm{SO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{S}(g) \rightleftharpoons 3 \mathrm{S}(s)+2 \mathrm{H}_{2} \mathrm{O}(g) $$ is the basis of a suggested method for removal of SO \(_{2}\) 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 \(\mathrm{K} ?\) (b) In principle, is this reaction a feasible method of removing \(S O_{2} ?\) (c) If \(P_{S O_{2}}=P_{H_{2} S}\) and the vapor pressure of water is 25 torr, calculate the equilibrium \(\mathrm{SO}_{2}\) pressure in the system at 298 K. (d) Would you expect the process to be more or less effective at higher temperatures?

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