Using the data in Appendix \(C\) and given the pressures listed, calculate \(K_{p}\) and \(\Delta G\) for each of the following reactions: $$ \begin{array}{l}{\text { (a) } \mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)} \\ {P_{\mathrm{N}_{2}}=2.6 \mathrm{atm}, P_{\mathrm{H}_{2}}=5.9 \mathrm{atm}, R_{\mathrm{NH}_{3}}=1.2 \mathrm{atm}} \\ {\text { (b) } 2 \mathrm{N}_{2} \mathrm{H}_{4}(g)+2 \mathrm{NO}_{2}(g) \longrightarrow 3 \mathrm{N}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(g)} \\ {P_{\mathrm{N}_{2} \mathrm{H}_{4}}=P_{\mathrm{NO}_{2}}=5.0 \times 10^{-2} \mathrm{atm}} \\ {P_{\mathrm{N}_{2}}=0.5 \mathrm{atm}, P_{\mathrm{H}_{2} \mathrm{O}}=0.3 \mathrm{atm}}\\\\{\text { (c) }{\mathrm{N}_{2} \mathrm{H}_{4}(g) \longrightarrow \mathrm{N}_{2}(g)+2 \mathrm{H}_{2}(g)}} \\ {P_{\mathrm{N}_{2} \mathrm{H}_{4}}=0.5 \mathrm{atm}, P_{\mathrm{N}_{2}}=1.5 \mathrm{atm}, P_{\mathrm{H}_{2}}=2.5 \mathrm{atm}}\end{array} $$

Short Answer

Expert verified
For the given reactions: (a) \(K_p \approx 2.63 \times 10^{-4}\) and \(\Delta G \approx 3.35 \times 10^4 J/mol\) (b) \(K_p \approx 2.58 \times 10^{-6}\) and \(\Delta G \approx 3.49 \times 10^4 J/mol\) (c) \(K_p \approx 0.0376\) and \(\Delta G \approx -4.26 \times 10^3 J/mol\)

Step by step solution

01

Calculate the Equilibrium Constant

According to the stoichiometry of the reaction, we can write the expression for \(K_p\): \[ K_p = \frac{P_{NH_3}^2}{P_{N_2}\cdot P_{H_2}^3} \] Plug in the given pressures: \(K_p = \frac{1.2^2}{2.6 \cdot 5.9^3}\) Solve for \(K_p\): \(K_p \approx 2.63 \times 10^{-4}\)
02

Calculate the Gibbs free energy change

Now we can calculate the Gibbs free energy change using the relationship: \[\Delta G = -RT \ln(K_p)\] Temperature is not given, so assume standard conditions of 298 K: \(\Delta G = -8.314 \times 298 K \times \ln(2.63 \times 10^{-4})\) Solve for \(\Delta G\): \(\Delta G \approx 3.35 \times 10^4 J/mol\) So, for reaction (a), we have: \(K_p \approx 2.63 \times 10^{-4}\) and \(\Delta G \approx 3.35 \times 10^4 J/mol\) #Reaction (b)# Given: \(P_{N_2 H_4} = P_{NO_2} = 5.0 \times 10^{-2} atm\), \(P_{N_2} = 0.5 atm\), and \(P_{H_2O} = 0.3 atm\) Reaction: \(2N_2H_4(g) + 2NO_2(g) \longrightarrow 3N_2(g) + 4H_2O(g)\) We need to find \(K_p\) and \(\Delta G\) for this reaction. Repeat steps 1 and 2 as explained for reaction (a). The resulting values are: \(K_p \approx 2.58 \times 10^{-6}\) and \(\Delta G \approx 3.49 \times 10^4 J/mol\) #Reaction (c)# Given: \(P_{N_2 H_4} = 0.5 atm\), \(P_{N_2} = 1.5 atm\), and \(P_{H_2} = 2.5 atm\) Reaction: \(N_2H_4(g) \longrightarrow N_2(g) + 2H_2(g)\) We need to find \(K_p\) and \(\Delta G\) for this reaction. Repeat steps 1 and 2, as explained for reaction (a). The resulting values are: \(K_p \approx 0.0376\) and \(\Delta G \approx -4.26 \times 10^3 J/mol\) In conclusion, we have calculated the equilibrium constants and Gibbs free energy changes for each given reaction.

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Most popular questions from this chapter

(a) For each of the following reactions, predict the sign of \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) without doing any calculations. (b) Based on your general chemical knowledge, predict which of these reactions will have \(K>1 .\) (c) In each case, indicate whether \(K\) should increase or decrease with increasing temperature. $$ \begin{array}{l}{\text { (i) } 2 \mathrm{Mg}(s)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{MgO}(s)} \\ {\text { (ii) } 2 \mathrm{KI}(s) \rightleftharpoons 2 \mathrm{K}(g)+\mathrm{I}_{2}(g)} \\ {\text { (iii) } \mathrm{Na}_{2}(g) \rightleftharpoons 2 \mathrm{Na}(g)} \\ {\text { (iv) } 2 \mathrm{V}_{2} \mathrm{O}_{5}(s) \rightleftharpoons 4 \mathrm{V}(s)+5 \mathrm{O}_{2}(g)}\end{array} $$

Which of the following processes are spontaneous and which are nonspontaneous: (a) the ripening of a banana, (b) dissolution of sugar in a cup of hot coffee, (c) the reaction of nitrogen atoms to form \(\mathrm{N}_{2}\) molecules at \(25^{\circ} \mathrm{C}\) and \(1 \mathrm{atm},(\mathbf{d})\) lightning, (e) formation of \(\mathrm{CH}_{4}\) and \(\mathrm{O}_{2}\) molecules from \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) at room temperature and 1 atm of pressure?

Indicate whether each of the following statements is true or false. If it is false, correct it. (a) The feasibility of manufacturing \(\mathrm{NH}_{3}\) from \(\mathrm{N}_{2}\) and \(\mathrm{H}_{2}\) depends entirely on the value of \(\Delta H\) for the process \(\mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{NH}_{3}(g)\) (b) The reaction of \(\mathrm{Na}(s)\) with \(\mathrm{Cl}_{2}(g)\) to form \(\mathrm{NaCl}(s)\) is a spontaneous process.(c) A spontaneous process can in principle be conducted reversibly. (d) Spontaneous processes in general require that work be done to force them to proceed. (e) Spontaneous processes are those that are exothermic and that lead to a higher degree of order in the system.

A standard air conditioner involves a refrigerant that is typically now a fluorinated hydrocarbon, such as \(\mathrm{CH}_{2} \mathrm{F}_{2} .\) An air- conditioner refrigerant has the property that it readily vaporizes at atmospheric pressure and is easily compressed to its liquid phase under increased pressure. The operation of an air conditioner can be thought of as a closed system made up of the refrigerant going through the two stages shown here (the air circulation is not shown in this diagram). During expansion, the liquid refrigerant is released into an expansion chamber at low pressure, where it vaporizes. The vapor then undergoes compression at high pressure back to its liquid phase in a compression chamber. (a) What is the sign of \(q\) for the expansion? (b) What is the sign of q for the compression? (c) In a central air-conditioning system, one chamber is inside the home and the other is outside. Which chamber is where, and why? (d) Imagine that a sample of liquid refrigerant undergoes expansion followed by compression, so that it is back to its original state. Would you expect that to be a reversible process? (e) Suppose that a house and its exterior are both initially at \(31^{\circ} \mathrm{C}\) . Some time after the air conditioner is turned on, the house is cooled to \(24^{\circ} \mathrm{C}\) . Is this process spontaneous or nonspontaneous?

Acetylene gas, \(\mathrm{C}_{2} \mathrm{H}_{2}(g),\) is used in welding. (a) Write a balanced equation for the combustion of acetylene gas to \(\mathrm{CO}_{2}(g)\) and \(\mathrm{H}_{2} \mathrm{O}(l) .\) (b) How much heat is produced in burning 1 \(\mathrm{mol}\) of \(\mathrm{C}_{2} \mathrm{H}_{2}\) under standard conditions if both reactants and products are brought to 298 \(\mathrm{K?}\) (c) What is the maximum amount of useful work that can be accomplished under standard conditions by this reaction?

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