Question

In a high temperature corrosion cell we have 5 vol% O2 and 500 vppm HCl. We know at high temperature the reaction is Deacon Process (600C) 4HCl(g)+O2(g)=2Cl2(g)+2H2O(g). We have thermodynamic phase diagram of a system (e.g., Fe-O2-Cl2) at 600 (log pO2 - x axis and log pCl2 in Y axis). How do we calculate the PCl2 and PO2 from the available data. Many thanks.