Consider a mixture of two ideal gases, $\mathrm{X}$ and $\mathrm{Y}$, with molar masses $\bar{M}_{\mathrm{X}}=10 \mathrm{~kg} / \mathrm{kmol}$ and $\bar{M}_{\mathrm{Y}}=20 \mathrm{~kg} / \mathrm{kmol}$, respectively, in a container. The total pressure in the container is $100 \mathrm{kPa}$, the total volume of the container is $10 \mathrm{~m}^3$ and the temperature of the contents of the container is $300 \mathrm{~K}$. If the mass of gas- $X$ in the container is $2 \mathrm{~kg}$, then the mass of gas- $Y$ in the container is ____________ $\mathrm{kg}$. (Rounded off to one decimal place)
Assume that the universal gas constant is $8314 \mathrm{~J} \mathrm{kmol}^{-1} \mathrm{~K}^{-1}$.