Multiple Choice
Nickel has ∆Hvap = 370.4 kJ/mol and ∆Svap = 123.3 J/mol•K. Will nickel boil at 2700 °C and 1 atm?
19. Chemical Thermodynamics
Gibbs Free Energy Calculations
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Calculate ΔG° (in kJ) for a reaction where ΔH° = -87 kJ, ΔS° = -223 J/K, and T = 298 K.
A
-87.0 kJ
B
-65.5 kJ
C
-20.6 kJ
D
-112.5 kJ
Verified step by step guidance1
Identify the formula to calculate the standard Gibbs free energy change (ΔG°) for a reaction: ΔG° = ΔH° - TΔS°.
Ensure all units are consistent. Here, ΔH° is given in kJ and ΔS° in J/K. Convert ΔS° from J/K to kJ/K by dividing by 1000: ΔS° = -223 J/K ÷ 1000 = -0.223 kJ/K.
Substitute the given values into the formula: ΔG° = (-87 kJ) - (298 K)(-0.223 kJ/K).
Calculate the product of temperature (T) and entropy change (ΔS°): 298 K × -0.223 kJ/K.
Subtract the result from the enthalpy change (ΔH°) to find ΔG°: ΔG° = -87 kJ - (result from previous step).
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