Q. To an evacuated vessel with movable piston under external pressure of 1 atm, 0.1 mole of He and 1.0 mole of an unknown compound (vapour pressure 0.68 atm at$0℃$) are introduced. Considering the ideal gas behaviour, the total volume (in litre) of the gases at $0℃$ is close to
A) 3
B) 5
C) 7
D) 9
Explanation
(c)
Since, the external pressure is 1.0 atm, the gas pressure is also 1.0 atm as piston is movable. Out of this 1.0 atm partial pressure due to unknown compound is 0.68 atm.
Therefore, partial pressure of He=1.00-0.68=0.32 atm.
$\Rightarrow Volume = \frac{n(He)RT}{p(He)}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{0.1 \times 0.082 \times 273}{0.32} = 7L$
$\Rightarrow Volume\ of\ container = Volume\ of\ He.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.