(A) The normal boiling point of isooctane (a gasoline component with a high octane rating) is 99.2 °C, and its Δ_vapH is 35.76 kJ mol^-1. Because isooctane and water have nearly identical boiling points, will they have nearly equal vapor pressures at room temperature? If not, which would you expect to be more volatile? Explain.

(B) The second electron affinity of oxygen is, by definition, the energy change for adding an electron to O^– to form O^2–:

The second electron affinity cannot be measured directly, but it can be obtained indirectly by using the Born–Haber cycle for an ionic compound containing the O^2– ion.

(a) Show that E_ea,2 can be calculated from the enthalpy of formation and lattice energy of MgO(s), the enthalpy of sublimation of Mg(s), the ionization energies of Mg, the bond energy of O₂ and the E_ea,1 for O(g).

(b) The lattice energy of MgO is -3925 kJ mol^-1. Combine this with other values in the text to estimate E_ea,2 for oxygen.

Transcribed Image Text:

O(g) + e- 0²-(g) Eea,2 = ?