Physics
posted by Sam .
An ideal gas is contained within closed box behind a removable wall. The walls of the container are insulated, so that no heat may be transferred from the system. Initially, the gas has an initial pressure P and an initial temperature T. The gas is then allowed to freely expand to twice the initial volume by the removal of the inside wall. Which of the following statements regarding the final pressure is true?
The final pressure is twice the initial pressure.
The final pressure is onehalf the initial pressure.
The final pressure is onefourth the initial pressure.
The final pressure is equal to the initial pressure.
The final pressure is four times the initial pressure.

http://www.schoolphysics.co.uk/age1619/Thermal%20physics/Gas%20laws/text/Adiabatic_change_equation/index.html
Note example problem with adiabatic expansion to twice volume. 
Would it be twice the initial pressure?