The standard free energy change for a chemical reaction is +13.3 kJ.What is the equilibrium constant for the reaction at 125°C? (R = 8.31 × 10−³ kJ/K)

Question

Quizplus · Accepted Answer

The equation linking the equilibrium constant, K, to the standard free energy change, ΔG°, is ΔG° = -RTlnK, where R is the gas constant and T is the temperature in Kelvin. Rearranging the equation, we get lnK = -ΔG°/RT. Substituting the given values, lnK = -13.3 kJ/(8.31×10-3 kJ/K/mol × 398 K) = 4.34. Taking the antilog of both sides, we get K = 10^4.34 = 2.5 × 10^-13. The closest option is D (1.8 × 10^-12), which is within one order of magnitude of the calculated answer.

The Standard Free Energy Change for a Chemical Reaction Is