Question

2) Write down a Born-Haber cycle for magnesium oxide (Mg0). Using the data provided below, determine the experimental value of the lattice enthalpy Uexp. Now calculate the lattice enthalpy Ucale (unit cell of Mg0 shown below). What do these values tell you about the bonding in Mg0? AHP(Mg0)--602 k]/mol Alto (Mg) = + 148 kJ/mol AH to (02) = +249 kJ/mol bond enthalpy (02)+498 k]/mol 16, (Mg) = +738 kJ/mol IE2 (Mg) +1451 k]/mol EA (O) = +142 kJ/mol EA2(0) =-798 kJ/mol (Question: what does this mean about the stability of O2(g)?) Hg FYI, for enthalpy of atomization data, see: http://www.webelements.com/periodicity/enthalpy atomisation/ Note: The results of the Born-Lande equation are not very sensitive to the value of the Born exponent n (= ar). The value of n is typically between 5 and 12. For mixed ion lattices, like NaCl and MgO, it is reasonable to use an average value of n = 8.

Answer 1