Question

The enthalpy of vaporisation of liquid diethyl ether is $26.0kJmo{l}^{-1}$ at its boiling point ${35.0}^{o}C.$
Calculate $△S$ for conversion of vapour to liquid at ${35.0}^{o}C$ in $J{K}^{-1}mo{l}^{-1}$.

• A. $-84.41$
• B. $+84.41$
• C. $-48.41$
• D. $+48.41$

Answer 1

The correct option is A $-84.41$

We know that, for conversion of vapour to liquid (condensation):
$△S_{cond.}=\frac{△H_{cond.}}{T}$
$△H_{cond.}=-△H_{vap.}$
putting the values,
$=-\frac{26\times {10}^3}{308}$
$\because H_{cond}=-26kJ$
$△S_{cond.}=-84.41J{K}^{-1}mo{l}^{-}1$