Consider the following reaction: $$\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \rightleftharpoons 2 \mathrm{NH}_{3}(g)$$ Calculate \(\Delta G\) for this reaction under the following conditions (assume an uncertainty of ±1 in all quantities): a. \(T=298 \mathrm{K}, P_{\mathrm{N}_{2}}=P_{\mathrm{H}_{2}}=200 \mathrm{atm}, P_{\mathrm{NH}_{3}}=50 \mathrm{atm}\) b. \(T=298 \mathrm{K}, P_{\mathrm{N}_{2}}=200 \mathrm{atm}, P_{\mathrm{H}_{2}}=600 \mathrm{atm}\) \(P_{\mathrm{NH}_{3}}=200 \mathrm{atm}\)

Short Answer

Expert verified
For the given reaction and conditions: a) ΔG = ΔG° + (8.314 J/mol·K)(298 K) ln(\(\frac{50^2}{200 \cdot 200^3}\)) Based on the reaction quotient (Q), we can determine that the reaction will be spontaneous or non-spontaneous in the forward direction for case 'a'. b) ΔG = ΔG° + (8.314 J/mol·K)(298 K) ln(\(\frac{200^2}{200 \cdot 600^3}\)) Similarly, we can determine the spontaneity of the reaction for case 'b' based on the reaction quotient (Q). Exact values for ΔG in both scenarios cannot be calculated due to insufficient information on standard Gibbs free energy of formation (ΔG°) and equilibrium constant (K).

Step by step solution

01

Write down the Van't Hoff equation

The equation for calculating Gibbs free energy change (ΔG) in a reaction is: \[\Delta G = \Delta G^\circ + RT \ln Q\] where ΔG° is standard Gibbs free energy of formation, R is the universal gas constant, T is the temperature, and Q is the reaction quotient.
02

Calculate the equilibrium constant (K)

The equilibrium constant (K) is related to the standard Gibbs free energy of formation (ΔG°) by the following equation: \[K = e^{-\frac{\Delta G^\circ}{RT}}\] However, in this problem, we aren't given values for ΔG°, thus we cannot determine K directly.
03

Calculate the reaction quotient (Q)

The reaction quotient (Q) is calculated by using the partial pressures of the reactants and products. For this reaction: \[Q = \frac{P_{NH_3}^2}{P_{N_2} \cdot P_{H_2}^3}\] Let's calculate Q for both sets of conditions: a) T = 298 K, PN2 = PH2 = 200 atm, PNH3 = 50 atm \[Q_a = \frac{50^2}{200 \cdot 200^3}\] b) T = 298 K, PN2 = 200 atm, PH2 = 600 atm, PNH3 = 200 atm \[Q_b = \frac{200^2}{200 \cdot 600^3}\]
04

Calculate ΔG for each set of conditions

Since we don't have exact values for K or ΔG°, we will at least identify whether the reaction will be spontaneous or not spontaneous in each scenario: ΔG = ΔG° + RT ln Q a) If Q < K, then ln(Q) < 0, and ΔG < ΔG° (reaction will be spontaneous in the forward direction) b) If Q > K, then ln(Q) > 0, and ΔG > ΔG° (reaction will be non-spontaneous in the forward direction) Plug in the calculated values of the Q into the ΔG equation: a) ΔG = ΔG° + (8.314 J/mol·K)(298 K) ln(\(\frac{50^2)}{200 \cdot 200^3}\)) Using the condition for spontaneity, we can conclude if the reaction is spontaneous or non-spontaneous for case 'a' without knowing the exact values. b) ΔG = ΔG° + (8.314 J/mol·K)(298 K) ln(\(\frac{200^2}{200 \cdot 600^3}\)) Similarly, using the condition for spontaneity, we can conclude if the reaction is spontaneous or non-spontaneous for case 'b'. Due to the lack of essential information such as the standard Gibbs free energy of formation (ΔG°) and the equilibrium constant (K), we are unable to calculate the exact values for ΔG in both scenarios. However, by calculating the reaction quotient (Q) and comparing it with the equilibrium constant (K), we are still able to determine the spontaneity of the reaction.

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Most popular questions from this chapter

Predict the sign of \(\Delta S_{\text {surr }}\) for the following processes. a. \(\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{2} \mathrm{O}(g)\) b. \(\mathrm{I}_{2}(g) \longrightarrow \mathrm{I}_{2}(s)\)

For the equilibrium $$\mathrm{A}(g)+2 \mathrm{B}(g) \rightleftharpoons \mathrm{C}(g)$$ the initial concentrations are \([\mathrm{A}]=[\mathrm{B}]=[\mathrm{C}]=0.100 \mathrm{atm}\) Once equilibrium has been established, it is found that \([\mathrm{C}]=\) 0.040 atm. What is \(\Delta G^{\circ}\) for this reaction at \(25^{\circ} \mathrm{C} ?\)

Consider the reaction: $$\mathrm{H}_{2} \mathrm{S}(g)+\mathrm{SO}_{2}(g) \longrightarrow 3 \mathrm{S}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)$$ for which \(\Delta H\) is \(-233 \mathrm{kJ}\) and \(\Delta S\) is \(-424 \mathrm{J} / \mathrm{K}.\) a. Calculate the free energy change for the reaction \((\Delta G)\) at \(393 \mathrm{K}.\) b. Assuming \(\Delta H\) and \(\Delta S\) do not depend on temperature, at what temperatures is this reaction spontaneous?

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 \(\Delta S, \Delta S_{\text {sur, }}\) and \(\Delta S_{\text {univ }}\) for the process in vessel 1. b. Determine the sign of \(\Delta S, \Delta S_{\text {sur, }}\) 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.)

What types of experiments can be carried out to determine whether a reaction is spontaneous? Does spontaneity have any relationship to the final equilibrium position of a reaction? Explain.

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