1. The activity of chromium in liquid Ni-Cr alloys was measured using the followhg cell : Pt I Cr(s), CrZO,(s) I Zr02(+CaO) I Ni-Cr(f), Cr203 I Pt The cell emf was measured to be 125 mV at 1,600″C for the Ni-Cr alloy of Nc, = 0.109. Calculate the activity of Cr in the alloy.
2. The oxygen content of molten iron can be measured using the following cell : pt I Cr(s), Cr203(s) I Zr02(+CaO) 1 Q (in liquid Fe) )MO Derive an equation which relates the measured emf to the oxygen content (wt%) in the Fe melt at 1,600″C. The following data are given : 2Cr + 402 = Cr20, AG& = -1,110,100 +247.32T, Jmole-‘ +02(g) =O(lwt?!) AGA =-117,150-2.8872, Jmole-‘ 1 wt?? in Fe melt standard st
