Question

At 373 K, steam and water are in equilibrium and ${△}_{vap}H=40.98kJmo{l}^{-1}.$ What will be entropy change for conversion of water into steam?
$H_2{O}_{\left(l\right)}\to H_2{O}_{\left(g\right)}$

• A. $109.8J{K}^{-1}mo{l}^{-1}$
• B. $31J{K}^{-1}mo{l}^{-1}$
• C. $21.98J{K}^{-1}mo{l}^{-1}$
• D. $326J{K}^{-1}mo{l}^{-1}$

Answer 1

The correct option is A $109.8J{K}^{-1}mo{l}^{-1}$

The change in Entropy for the vaporisation process is given as:

$△S_{vap}=\frac{△H_{vap}}{T_b}=\frac{40.98\times 1000Jmo{l}^{-1}}{373K}$

$=109.8J{K}^{-1}mo{l}^{-1}$