Question

The valve on a cylinder containing initially 1 liters of an ideal gas at 7 atm and ${25}^{o}C$ is opened to the atmosphere, Whose the pressure is 760 torr and the temperature is ${25}^{o}C$. Assuming that the process isothermal, how much work (in L.atm) is done on the atmosphere by the action of expansion ?

Answer 1

molality = $\frac{\Delta T_b}{K_b}=\frac{2}{0.76}=2.63$ mol k/g

and molality of pure water is $55.6$ mol k/g

now, vapour pressure = $\frac{p_0-p}{p_0}=\frac{n}{n+N}$

$=\frac{760-p}{760}=\frac{2.63}{55.56}$

on substituting the value and solving it we get

the value as $\therefore p=724$ torr. (ans)