Question

How do you find the pressure in a container if you don't have the temperature? 

Answer 1

It depends on the process.
Like for example if the process is isothermal(temperature is constant), you can use,
PV = constant or P1V1 = P2V2 where P1V1 are initial conditions and P2V2 are final.


For adiabatic process,

PV^gamma = constant or P1V1 ^gamma = P2V2 ^gamma.

where gamma = Cp
                          ------
                           Cv
Cp = specific heat at constant pressure and Cv = specific at constant volume.

Value of Gamma will be given in question.
Hope this helps!