Question

The vapour pressure of water at ${80}^{\circ }\text{C}$ is $355\text{mm}$ of $Hg$. The total pressure of a $1\text{L}$ vessel containing $O_2$ saturated with water at ${80}^{\circ }\text{C}$ is $760\text{mm}$ of $Hg$. The contents of the vessel are pumped into a $0.3\text{L}$ vessel at the same temperature. What is the partial pressure of $O_2$?

• A. $1350\text{mm of Hg}$
• B. $2178.3\text{mm of Hg}$
• C. $121.5\text{mm of Hg}$
• D. $355\text{mm of Hg}$

Answer 1

The correct option is A $1350\text{mm of Hg}$

Volume of $O_2=1\text{L}$
$P_{O_2}=760-355=405\text{mm of Hg}$
Since the tempearture is constant,
Using Boyle's law:
$P_{O_2}{V}_{O_2}=P_{O_2}^{\prime }{V}_{O_2}^{\prime }$
$1\text{L}\times 405\text{mm}=0.3\text{L}\times P_{O_2}^{\prime }$
$\therefore P_{O_2}^{\prime }=1350\text{mm of Hg}$