Multiple Choice
Which of the following conditions will result in a spontaneous reaction at standard conditions according to the Gibbs free energy equation ΔG°rxn = ΔH°rxn - TΔS°rxn?
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19. Chemical Thermodynamics
Gibbs Free Energy Calculations
Multiple Choice
The dissolution of ammonium nitrate is given by the reaction: NH4NO3(s) -> NH4+(aq) + NO3-(aq). Assuming that the values of ΔH° and ΔS° do not change appreciably with temperature, which of the following is the correct expression to calculate the ΔG° value for the reaction?
A
ΔG° = TΔS° - ΔH°
B
ΔG° = ΔH° + TΔS°
C
ΔG° = ΔH° / TΔS°
D
ΔG° = ΔH° - TΔS°
Verified step by step guidance1
Understand the Gibbs free energy equation: The Gibbs free energy change (ΔG°) is a thermodynamic quantity that can be calculated using the equation ΔG° = ΔH° - TΔS°, where ΔH° is the change in enthalpy, T is the temperature in Kelvin, and ΔS° is the change in entropy.
Identify the components of the equation: In the equation ΔG° = ΔH° - TΔS°, ΔH° represents the heat absorbed or released during the reaction, T is the absolute temperature, and ΔS° represents the change in disorder or randomness of the system.
Recognize the significance of each term: ΔH° indicates whether the reaction is endothermic or exothermic, TΔS° represents the temperature-dependent change in entropy, and ΔG° determines the spontaneity of the reaction. A negative ΔG° implies a spontaneous process.
Apply the equation to the given reaction: For the dissolution of ammonium nitrate, use the equation ΔG° = ΔH° - TΔS° to calculate the Gibbs free energy change, considering the values of ΔH° and ΔS° provided or assumed constant.
Evaluate the options: Compare the given expressions for calculating ΔG° and identify that the correct expression is ΔG° = ΔH° - TΔS°, as it aligns with the standard Gibbs free energy equation used in thermodynamics.
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