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^(@)C` are introduced Considering the ideal gas behaviour the total volume (in litre) of the gases at `0^(@)C` is close to .

Answer

7

Explanation

Let volume of vessel `= VL`
In the vapour of compound.
`PV = n_(g)RT`
`0.68 xx V = n_(g) xx 0.082 xx 273`....(i)
Total pressure = External pressure,
`1 xx V = (n_(g) + n_(He)) xx 0.082 xx 273`...(ii)
Dividing eqn. (ii) by eqn. (i)
`(1)/(0.68) = (n_(g) + n_(He))/(n_(g))`
`n_(g) = 0.68 n_(g) + 0.68 n_(He)`
`= 0.68 n_(g) + 0.68 xx 0.1`
`0.32 n_(g) = 0.068`
`n_(g) = 0.2125`
From eqn. (ii),
`V = (0.2125 + 0.1) xx 0.082 xx 273`
`= 6.99 = 7L`