States of Matter - Result Question 74
####74. An evacuated glass vessel weighs $50.0 g$ when empty $148.0 g$ when filled with a liquid of density $0.98 g mL^{-1}$ and $50.5 g$ when filled with an ideal gas at $760 mm Hg$ at $300 K$. Determine the molar mass of the gas.
(1998, 3M)
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Answer:
Correct Answer: 74. $\left(2.46 m^{3}\right)$
Solution:
- Mass of liquid $=148-50=98 g$
$\Rightarrow$ Volume of liquid $=\frac{98}{0.98}=100 mL=$ volume of flask
mass of gas $=50.5-50=0.50 g$
Now applying ideal gas equation : $p V=\left(\frac{w}{M}\right) R T$
$\Rightarrow \quad M=\frac{w R T}{p V}=\frac{0.5 \times 0.082 \times 300}{1 \times 0.1}=123 g mol^{-1}$
