Question

The enthalpy of vapourisation of a liquid is 30 kJ mol^–1 and entropy of vapourisation is 75mol^–1 K. The boiling point of the liquid at 1 atm is

• A. 250 K
• B. 400 K
• C. 450 K
• D. 600 K

Answer 1

Answer: (B)

400 K

Answer 2

$\Delta S_{v} = \frac{\Delta H_{v}}{T_{b}}$

$30kJ = 30000J$

$\Delta H_{v} = 30000J$;$\Delta S_{v} = 75mole^{- 1}K$

; $T_{b} = \frac{30000}{75} = 400K$