Textbook Problem

A $\text{5}00-\text{mL}$sample of ${\text{O}}_{\text{2}}$gas at $\text{24 }°\text{C}$was prepared by decomposing a $\text{3}\%$aqueous solution of hydrogen peroxide, ${\text{H}}_{\text{3}}{\text{O}}_{\text{2}}$, in the presence of a small amount of manganese catalyst by the reaction

msp;  ${\text{2H}}_{\text{2}}{\text{O}}_{\text{2}}\left(aq\right) {\text{2H}}_{\text{2}}\text{O}\left(g\right)+{\text{O}}_{\text{2}}\left(g\right)$

e oxygen mus. prepared was collected by displacement of water. The total pressure of gas collected was 755 mm Hg. What is the partial pressure of O₂in the mixture? How many moles of O₂are in the mixture? (The vapor pressure of water at $\text{24 }°\text{C}$is $\text{23 mm Hg}$.)