Chemistry Daily Challenge 17-July-2015

Chemistry Level 3

One mole of \(\ce{N2O4}(g)\) at 300 K is kept in a closed container at 1 atm. It is heated to 600 K when 20% by mass of \(\ce{N2O4}\) decomposed to \(\ce{NO2}(g).\) What is the resultant pressure in atm?