a student has a 0.58g sample of a mixture of mercury(II) oxide (which decomposes upon heating) and zinc (II) oxide (which does not). she decomposes the mixture in the exact same manner as the lab, and isolates 154 mL of water at the end. if the water temperature is 24oC and the atmospheric pressure is 742 torr, what was the percent by mass of mercury oxide in the mixture