To calculate the equilibrium constant Kc of the reaction at 25C, we need the standard Gibbs free energy change G of the reaction. For the given reaction:N2 g + 3H2 g 2NH3 g The standard Gibbs free energy change G at 25C is -33.6 kJ/mol. Now, we can use the following equation to calculate the equilibrium constant Kc :G = -RT ln Kc Where:G = -33.6 kJ/molR = 8.314 J/ molK gas constant T = 25C = 298.15 KFirst, we need to convert G to J/mol:G = -33.6 kJ/mol * 1000 J/kJ = -33600 J/molNow, we can rearrange the equation to solve for Kc:ln Kc = -G / RT Kc = e^-G / RT Plugging in the values:Kc = e^- -33600 J/mol / 8.314 J/ molK * 298.15 K Kc 6.02 x 10^2So, the equilibrium constant Kc for the reaction at 25C is approximately 6.02 x 10^2.Now, let's consider the effect of a catalyst on the equilibrium position. A catalyst speeds up the rate of a reaction by lowering the activation energy but does not affect the equilibrium constant Kc . Therefore, the equilibrium constant Kc will remain the same, 6.02 x 10^2, with or without a catalyst.In conclusion, the equilibrium constant Kc for the reaction at 25C is approximately 6.02 x 10^2, and the presence of a catalyst does not affect the equilibrium position.