Answer
The partial pressure of the $O_{2}$ gas is $0.34 atm$
Work Step by Step
Using Dalton's Law of Partial Pressure, we can find the pressure an individual gas exerts in a mixture of gases.
$Partial Pressure = Mole Fraction of Gas\times Total Pressure$
Since we are told that there is $4$ % of $O_{2}$, we can determine the mole fraction simply by converting the percent of $O_{2}$ gas into a number by dividing by 100 to get $0.4$
Therefore, the partial pressure of $O_{2}$ is $0.04\times 8.5 atm =0.34 atm $
