1.31 × 10⁴ grams.
Assume that oxygen acts like an ideal gas. In other words, assume that the oxygen here satisfies the ideal gas law:
[tex]P \cdot V = n \cdot R\cdot T[/tex],
where
Apply the ideal gas law to find [tex]n[/tex]:
[tex]n = \dfrac{P\cdot V}{R\cdot T} = \dfrac{{\bf 10^{8}\;\textbf{Pa}}\times 10^{-2}\;\text{m}^{3}}{8.314 \;\text{Pa}\cdot\text{m}^{3}\cdot\text{K}^{-1}\cdot\text{mol}^{-1}\times 293.15\;\text{K}} = 410.3\;\text{mol}[/tex].
In other words, there are 410.3 moles of O₂ molecules in that container.
There are two oxygen atoms in each O₂ molecules. The mass of mole of O₂ molecules will be [tex]{\bf 2}\times 16.00 = 32.00\;\text{g}[/tex]. The mass of 410.3 moles of O₂ will be:
[tex]410.3 \times 32.00 = 1.31\times10^{4}\;\text{g}[/tex].
What would be the mass of oxygen in the container if the pressure is approximately the same as STP at [tex]10^{5}\;\textbf{Pa}[/tex] or [tex]10^{2}\;\text{kPa}[/tex] instead?