A vessel containing 0.1 m3 of air at 76 cm of Hg is connected to an evacuated vessel of capacity 0.09 m3. The resultant air pressure is:

Due to free expansion , temperature of the gas remains constant .At constant temperature         P1V1 = P2V2           P2 = (V1V2)P1 = 0.1 m30.1+0.09×76 cm of Hg              = 40 cm of Hg