A vessel of volume $27 \times 10^{4}\text{ cc}$ contains a mixture of Hydrogen (molar mass $= 2\text{ g mol}^{-1}$) and Oxygen (molar mass $= 32\text{ g mol}^{-1}$) gas at standard temperature and pressure (S.T.P.). If the mass of hydrogen is $16\text{ g}$, find the mass of oxygen gas contained in the vessel.