Answer:
a) E°=3*2.37 -2*1.66 = 3.79 V
b) the favored direction is 3Mg +2Al^(3+) ----> 3Mg^(2+) + 2Al
Explanation:
3Mg + 2Al^(3+) ---> 3Mg^(2+) + 2Al
a)
Mg         ---> Mg^(2+) + 2e-  , E°= +2.37V   /*3
Al^(3+) + 3 e - --> Al           , E° = - 1.66V  /*2
3Mg +2Al^(3+) ----> 3Mg^(2+) + 2Al ,   E°=3*2.37 -2*1.66 = 3.79 Volt
b)  ΔG°= − nFE° = - 6 mol e-*96485 J/Volt*mol e- * 3.79Volt  < 0,
so the favored direction is 3Mg +2Al^(3+) ----> 3Mg^(2+) + 2Al