객관식
What is the equilibrium constant (K) at 305 K when the standard Gibbs free energy change (ΔG°) is +4.87 kJ/mol?
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19. Chemical Thermodynamics
Gibbs Free Energy Calculations
객관식
What is ΔG (in kJ) for the formation of solid UF6 from uranium and fluorine at 25 °C when the partial pressure of F2 is 0.045 atm, given that the standard free energy of formation of UF6(s) is -2068 kJ/mol? Is the reaction spontaneous in the forward or the reverse direction?
A
-2068 kJ, spontaneous in the forward direction
B
-2075 kJ, spontaneous in the reverse direction
C
-2060 kJ, spontaneous in the reverse direction
D
-2075 kJ, spontaneous in the forward direction
검증된 단계별 안내1
Identify the reaction: The formation of solid UF6 from uranium and fluorine can be represented as: U(s) + 3F2(g) → UF6(s).
Understand the concept: The Gibbs free energy change (ΔG) for a reaction can be calculated using the equation ΔG = ΔG° + RTlnQ, where ΔG° is the standard Gibbs free energy change, R is the universal gas constant (8.314 J/mol·K), T is the temperature in Kelvin, and Q is the reaction quotient.
Convert temperature: Convert the given temperature from Celsius to Kelvin by adding 273.15. So, T = 25 + 273.15 = 298.15 K.
Calculate the reaction quotient (Q): For the reaction U(s) + 3F2(g) → UF6(s), the reaction quotient Q is given by the expression Q = [UF6]/[F2]^3. Since UF6 is a solid, its activity is 1, and Q = 1/(0.045)^3.
Substitute values into the ΔG equation: Use the equation ΔG = ΔG° + RTlnQ, where ΔG° = -2068 kJ/mol, R = 8.314 J/mol·K (convert to kJ by dividing by 1000), T = 298.15 K, and Q is calculated from the previous step. Calculate ΔG to determine the spontaneity of the reaction.
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