Textbook Question
(a) For a process that occurs at constant temperature, does the change in Gibbs free energy depend on changes in the enthalpy and entropy of the system?
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Ch.19 - Chemical Thermodynamics
Chapter 19, Problem 56
A certain reaction has ΔH° = +23.7 kJ and ΔS° = +52.4 J>K. (c) Calculate ΔG° for the reaction at 298 K. (d) Is the reaction spontaneous at 298 K under standard conditions?
Verified step by step guidance1
Step 1: Understand the relationship between Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) using the equation: ΔG° = ΔH° - TΔS°, where T is the temperature in Kelvin.
Step 2: Convert the entropy change (ΔS°) from J/K to kJ/K to match the units of ΔH°. Since 1 kJ = 1000 J, divide ΔS° by 1000.
Step 3: Substitute the given values into the equation: ΔH° = +23.7 kJ, ΔS° (converted to kJ/K), and T = 298 K.
Step 4: Calculate the term TΔS° by multiplying the temperature (298 K) by the converted ΔS° value.
Step 5: Substitute the values of ΔH° and TΔS° into the equation ΔG° = ΔH° - TΔS° to find ΔG°. Determine if the reaction is spontaneous by checking if ΔG° is negative.
Related Practice
Open Question
(a) Is the standard free-energy change, ΔG°, always larger than ΔG? (b) For any process that occurs at constant temperature and pressure, what is the significance of ΔG = 0? (c) For a certain process, ΔG is large and negative. Does this mean that the process necessarily has a low activation barrier?
Textbook Question
For a certain chemical reaction, ΔH° = -35.4 kJ and ΔS° = -85.5 J/K. (b) Does the reaction lead to an increase or decrease in the randomness or disorder of the system?
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Open Question
Using data in Appendix C, calculate ΔH°, ΔS°, and ΔG° at 298 K for each of the following reactions. (a) H₂(g) + F₂(g) → 2 HF(g) (b) C(s, graphite) + 2 Cl₂(g) → CCl₄(g) (c) 2 PCl₃(g) + O₂(g) → 2 POCl₃(g) (d) 2 CH₃OH(g) + H₂(g) → C₂H₆(g) + 2 H₂O(g)
Textbook Question
Use data in Appendix C to calculate ΔH°, ΔS°, and ΔG° at 25 °C for each of the following reactions.
c. 2 P(s) + 10 HF(g) → 2 PF5(g) + 5 H2(g)
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Textbook Question
Using data from Appendix C, calculate ΔG° for the following reactions. Indicate whether each reaction is spontaneous at 298 K under standard conditions. (a) 2 SO2(g) + O2(g) → 2 SO3(g)
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