The ideal gas law.
PV=nRT
pressure x volume = moles x Faraday's constant x Temp Kelvin (C+273)
Original data
Pressure 1 atmosphere
Volume 1 liter
Temp 25C = 298K
New data
Volume 0.5 liter
pressure X
Temp 260C = 533K
P1v1T1 = P2v2T2
plug and chug.
(1)(1)(293) = (x)(0.5)(533)
Solve for X, which is the new pressure.
