A container with a volume of  $20.0 \mathrm{L}$ holds ${\mathrm{N}}_2\left(\mathrm{g}\right)$ and ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$ at 300 K and 1.0 atm. The liquid water is then decomposed completely into  ${\mathrm{H}}_2\left(\mathrm{g}\right)$ and ${\mathrm{O}}_2\left(\mathrm{g}\right)$ by any means, at constant temperature. If the final pressure becomes 1.86 atm, what was the mass of water (in gm) present initially. Neglect the initial volume of water. [Given : Vapour pressure of water at  $300 \mathrm{K}=0.04 \mathrm{atm},\mathrm{R}=0.08 \mathrm{L}-\mathrm{atm}/\mathrm{K}-\mathrm{mol}]$