chemistry help!!
posted by Joanie .
a gaseous mixture contains 1 mol of O2 and 2 mol of CO2, exerting a total pressure of 1.5 atm. what amount of CH4 must be added to the mixture in order to increase the total pressure to 2 atm. (assume no gas escapes and there is no change in total volume)
the answer is 1 mol but i do not know how to get to that answer!

P1/n1 = P2/n2
P1 is the original total pressure (1.5 atm), n1 is the total moles: (1 mol O2 + 2 mol CO2= 3 moles total.)
P2 is the new total pressure (2 atm), n2 is the new total moles, which is 3 moles + x moles CH4 added.
1.5/3 = 2/ (3+x)
solve for x
x= moles CH4 added= 1 mol