The Ostwald process for the commercial production of nitric acid involves three steps: a. Calculate \(\Delta H^{\circ}, \Delta S^{\circ}, \Delta G^{\circ}\), and \(K\) (at \(298 \mathrm{~K}\) ) for each of the three steps in the Ostwald process (see Appendix 4 ). b. Calculate the equilibrium constant for the first step at \(825^{\circ} \mathrm{C}\), assuming \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) do not depend on temperature. c. Is there a thermodynamic reason for the high temperature in the first step, assuming standard conditions?

Short Answer

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In the Ostwald process, the three steps for commercial production of nitric acid involve the following reactions: 1. \(4 \mathrm{NH_{3}(g)} + 5 \mathrm{O_{2}(g)} \rightarrow 4 \mathrm{NO(g)} + 6 \mathrm{H_{2}O(g)}\) 2. \(2 \mathrm{NO(g)} + \mathrm{O_{2}(g)} \rightarrow 2 \mathrm{NO_{2}(g)}\) 3. \(\mathrm{NO_{2}(g)} + \mathrm{H_{2}O(l)} \rightarrow \mathrm{HNO_{3}(aq)} + \mathrm{NO(g)}\) After calculating the \(\Delta H^{\circ}, \Delta S^{\circ},\) and \(\Delta G^{\circ}\) values for each step, we can calculate the equilibrium constant \(K\) at \(298 \mathrm{~K}\) using the relation \(K = e^{[-\Delta G^{\circ}/(RT)]}\). For the first step at \(825^{\circ} \mathrm{C}\), we can use the Van't Hoff equation to calculate the equilibrium constant \(K\): \(K = e^{[\Delta S^{\circ}/R - \Delta H^{\circ}/(RT)]}\). The high temperature in the first step ensures that the reaction moves forward because the rate of the reaction depends on temperature. Moreover, at higher temperatures, the entropy becomes more significant, and since the reaction has a positive entropy change, it suggests a more spontaneous reaction at high temperatures. Thus, the high temperature in the first step helps the Ostwald process run efficiently and ensures the desired product formation.

Step by step solution

01

Calculate thermodynamic properties for each step

Refer to Appendix 4 of the book and use the given thermodynamic data to find the \(\Delta H^{\circ}, \Delta S^{\circ},\) and \(\Delta G^{\circ}\) for each step: Step 1: \(\Delta H^{\circ} = 4\Delta H_{f}^{\circ}(\mathrm{NO}) - (4\Delta H_{f}^{\circ}(\mathrm{NH_{3})} + 5\Delta H_{f}^{\circ}(\mathrm{O_{2})})\) \(\Delta S^{\circ} = (4S^{\circ}(\mathrm{NO}) + 6S^{\circ}(\mathrm{H_{2}O}) - (4S^{\circ}(\mathrm{NH_{3})} + 5S^{\circ}(\mathrm{O_{2})})\) \(\Delta G^{\circ} = 4\Delta G_{f}^{\circ}(\mathrm{NO}) - (4\Delta G_{f}^{\circ}(\mathrm{NH_{3})} + 5\Delta G_{f}^{\circ}(\mathrm{O_{2})})\) Step 2: Similar calculations as in step 1, for the second reaction. Step 3: Similar calculations as in step 1, for the third reaction. After calculating the \(\Delta H^{\circ}, \Delta S^{\circ},\) and \(\Delta G^{\circ}\) values for each step, we can calculate the equilibrium constant \(K\) at \(298 \mathrm{~K}\) using the following relation: \(K = e^{[-\Delta G^{\circ}/(RT)]}\)
02

Calculate equilibrium constant for the first step at \(825^{\circ} \mathrm{C}\)

To find the equilibrium constant for the first step at \(825^{\circ} \mathrm{C}\), assuming \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) do not depend on temperature, we can use the Van't Hoff equation: \(\frac{\Delta H^{\circ}}{T} = \frac{\Delta S^{\circ}}{R} \ln(K)\) Rearrange to solve for K: \(K = e^{[\Delta S^{\circ}/R - \Delta H^{\circ}/(RT)]}\) Now, plug in the values of \(\Delta H^{\circ}\), \(\Delta S^{\circ}\), R, and temperature (in Kelvin, \(825^{\circ} \mathrm{C} = 1098 \mathrm{K}\)) and calculate the equilibrium constant \(K\).
03

Discuss the thermodynamic reason for the high temperature in the first step

The high temperature in the first step ensures that the reaction moves forward because the rate of the reaction depends on temperature. Moreover, at higher temperatures, the entropy becomes more significant, and since the reaction has a positive entropy change, it suggests a more spontaneous reaction at high temperatures. In conclusion, the high temperature in the first step helps the Ostwald process run efficiently and ensures the desired product formation.

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Most popular questions from this chapter

Given the values of \(\Delta H\) and \(\Delta S\), which of the following changes will be spontaneous at constant \(T\) and \(P ?\) a. \(\Delta H=+25 \mathrm{~kJ}, \Delta S=+5.0 \mathrm{~J} / \mathrm{K}, T=300 . \mathrm{K}\) b. \(\Delta H=+25 \mathrm{~kJ}, \Delta S=+100 . \mathrm{J} / \mathrm{K}, T=300 . \mathrm{K}\) c. \(\Delta H=-10 . \mathrm{kJ}, \Delta S=+5.0 \mathrm{~J} / \mathrm{K}, T=298 \mathrm{~K}\) d. \(\Delta H=-10 . \mathrm{kJ}, \Delta S=-40 . \mathrm{J} / \mathrm{K}, T=200 . \mathrm{K}\)

For ammonia \(\left(\mathrm{NH}_{3}\right.\) ), the enthalpy of fusion is \(5.65 \mathrm{~kJ} / \mathrm{mol}\) and the entropy of fusion is \(28.9 \mathrm{~J} / \mathrm{K} \cdot \mathrm{mol}\). a. Will \(\mathrm{NH}_{3}(s)\) spontaneously melt at \(200 . \mathrm{K}\) ? b. What is the approximate melting point of ammonia?

Consider two perfectly insulated vessels. Vessel 1 initially contains an ice cube at \(0^{\circ} \mathrm{C}\) and water at \(0^{\circ} \mathrm{C}\). Vessel 2 initially contains an ice cube at \(0^{\circ} \mathrm{C}\) and a saltwater solution at \(0^{\circ} \mathrm{C}\). Consider the process \(\mathrm{H}_{2} \mathrm{O}(s) \rightarrow \mathrm{H}_{2} \mathrm{O}(l)\) a. Determine the sign of \(\Delta S, \Delta S_{\text {surr }}\), and \(\Delta S_{\text {univ }}\) for the process in vessel 1 . b. Determine the sign of \(\Delta S, \Delta S_{\text {surt }}\), and \(\Delta S_{\text {univ }}\) for the process in vessel 2 . (Hint: Think about the effect that a salt has on the freezing point of a solvent.)

Consider two reactions for the production of ethanol: $$\begin{array}{l}\mathrm{C}_{2} \mathrm{H}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(l) \\\ \mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(l)+\mathrm{H}_{2}(g) \end{array}$$ Which would be the more thermodynamically feasible at standard conditions? Why?

Consider the following reaction at \(298 \mathrm{~K}\) : $$2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{SO}_{3}(g)$$ An equilibrium mixture contains \(\mathrm{O}_{2}(\mathrm{~g})\) and \(\mathrm{SO}_{3}(g)\) at partial pressures of \(0.50\) atm and \(2.0\) atm, respectively. Using data from Appendix 4 , determine the equilibrium partial pressure of \(\mathrm{SO}_{2}\) in the mixture. Will this reaction be most favored at a high or a low temperature, assuming standard conditions?

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