Multiple Choice
A redox reaction has an equilibrium constant of K = 1.2 x 10^3. Which statement is true regarding ΔG°_rxn and E°_cell for this reaction?
19. Chemical Thermodynamics
Gibbs Free Energy And Equilibrium
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Calculate the Gibbs free energy change (ΔGᵣₓₙ) at 298 K for the reaction N₂ (g) + 3 H₂ (g) ⇌ 2 NH₃ (g) given the standard Gibbs free energy change (ΔG° = -33.3 kJ) and the partial pressures: P(N₂) = 1.5 atm, P(H₂) = 4.5 atm, P(NH₃) = 1.0 atm.
A
-33.3 kJ
B
-40.5 kJ
C
-25.0 kJ
D
-29.8 kJ
Verified step by step guidance1
Start by understanding the relationship between the Gibbs free energy change (ΔGᵣₓₙ) and the standard Gibbs free energy change (ΔG°) using the equation: ΔGᵣₓₙ = ΔG° + RT ln(Q), where R is the universal gas constant (8.314 J/mol·K), T is the temperature in Kelvin, and Q is the reaction quotient.
Calculate the reaction quotient (Q) using the partial pressures given. For the reaction N₂ (g) + 3 H₂ (g) ⇌ 2 NH₃ (g), the expression for Q is: Q = (P(NH₃)²) / (P(N₂) × P(H₂)³). Substitute the given partial pressures into this expression.
Convert the standard Gibbs free energy change (ΔG°) from kJ to J by multiplying by 1000, since the gas constant R is in J/mol·K.
Substitute the values of ΔG°, R, T, and Q into the equation ΔGᵣₓₙ = ΔG° + RT ln(Q) to find the Gibbs free energy change at the given conditions.
Ensure all units are consistent and perform the calculation to find the value of ΔGᵣₓₙ, which will give you the Gibbs free energy change for the reaction at 298 K.
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