A sealed vessel contains a gaseous mixture of H2 and excess O2. The mixture is at 500 K and has a total pressure of 140 kPa. After all of the hydrogen is reacted, the total pressure of the system measured at the same temperature is found to be 100 spa. what was the partial pressure of the O2 gas in the initial mixture? the unbalanced equation is
H2(g)+O2(g) --> H2O (g)