What is the value of the mean ionic activity coe?cient for Ce2(SO4)3 when the electromotive force (EMF) for the cell: Ce(s) | Ce2(SO4)3(aq) | Hg2SO4(s) | Hg(l) is 3.208 V at 25 oC and constant pressure of 1 bar. The molality of Ce2(SO4)3 is 0.0170 mol kg?1 . Use the following standard EMF values: for Ce3+| Ce E0 = ?2.483 V and for SO2?4| Hg2SO4 | Hg E0 = 0.6125 V.