A mixture in which the mole ratio of $H_2$ and $O_2$ is 2 : 1 is used to prepare water by the reaction $2H_2(g)+O_2(g)\rightarrow 2H_2O(g)$.The total pressure in the container is 0.8atm at $20^{\large\circ}C$ before the reaction.Determine the final pressure at $120^{\large\circ}C$ after reaction assuming 80% yield of water.