States of Matter 1 Question 66
66. To an evacuated vessel with movable piston under external pressure of $1 \mathrm{~atm}, 0.1$ mole of $\mathrm{He}$ and 1.0 mole of an unknown compound (vapour pressure $0.68 \mathrm{~atm}$ at $0^{\circ} \mathrm{C}$ ) are introduced. Considering the ideal gas behaviour, the total volume (in litre) of the gases at $0^{\circ} \mathrm{C}$ is close to
(2011)
Subjective Questions
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Answer:
Correct Answer: 66. $(7 \mathrm{~L})$
Solution:
- Since, the external pressure is $1.0 \mathrm{~atm}$, the gas pressure is also $1.0 \mathrm{~atm}$ as piston is movable. Out of this $1.0 \mathrm{~atm}$ partial pressure due to unknown compound is $0.68 \mathrm{~atm}$.
Therefore, partial pressure of $\mathrm{He}$
$$ \begin{aligned} & =1.00-0.68=0.32 \mathrm{~atm} . \ \Rightarrow \quad \text { Volume } & =\frac{n(\mathrm{He}) R T}{p(\mathrm{He})}=\frac{0.1 \times 0.082 \times 273}{0.32}=7 \mathrm{~L} \end{aligned} $$
$\Rightarrow$ Volume of container $=$ Volume of He.
