To calculate the standard change in free energy and the equilibrium constant for the reaction between NO2 and N2O4, use the standard free energies of formation from the appendix and apply the corresponding formulas. Then, to find the equilibrium concentration, use an ICE table approach with the provided initial conditions.
The equilibrium reaction between nitrogen dioxide (NO2) and dinitrogen tetroxide (N2O4) is given as 2 NO2(g) ⇌ N2O4(g).
To calculate the standard change in free energy (∆rxnG°) and the equilibrium constant (K) from the appendix, we need the standard free energies of formation for both NO2 and N2O4. Assuming standard conditions and that the requisite free energies of formation are provided in the Appendix 2, one would apply the formula:
∆rxnG° = ∆fG°(products) - ∆fG°(reactants).
To calculate the reaction's equilibrium constant K, we could use the relationship between ∆rxnG° and K:
∆rxnG° = -RTlnK,
where R is the gas constant and T is the temperature in Kelvin. The equilibrium concentration ξ for the reaction can also be calculated given initial conditions and the equilibrium constant. For 1.0 mol of NO2 initially present in a 20.0-L system, the initial concentration is 0.050 M. We would let ξ represent the change in moles of NO2, then solve for ξ using the ICE table method (Initial, Change, Equilibrium) and the calculated K.