Multiple Choice
What is ΔG° (in kJ/mol) for a redox reaction where two electrons are transferred with E°cell = -0.206 V?
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19. Chemical Thermodynamics
Gibbs Free Energy Calculations
Multiple Choice
What is the entropy change (ΔS) of a reaction that has an enthalpy change (ΔH) of -70 kJ and a Gibbs free energy change (ΔG) of 18 kJ at a constant temperature of 76 degrees Celsius?
A
-0.92 kJ/K
B
-0.29 kJ/K
C
0.29 kJ/K
D
0.92 kJ/K
Verified step by step guidance1
Start by understanding the relationship between Gibbs free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS) at a constant temperature. This relationship is given by the equation: ΔG = ΔH - TΔS.
Rearrange the equation to solve for the entropy change (ΔS): ΔS = (ΔH - ΔG) / T.
Convert the temperature from degrees Celsius to Kelvin, since thermodynamic calculations require temperature in Kelvin. Use the conversion formula: T(K) = T(°C) + 273.15. For this problem, T = 76 + 273.15.
Substitute the given values into the rearranged equation. Use ΔH = -70 kJ, ΔG = 18 kJ, and the converted temperature in Kelvin.
Perform the calculation to find ΔS. Remember to keep track of units, ensuring that the result for ΔS is in kJ/K.
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