Consider the following liquid-vapour equilibrium. Liquid Vapour Which of the following relations is correct ?
- d PdT2 = - HvT2
- d PdT = HvRT2
- d GdT2 = HvRT2
- d PdT = - HvRT
Answer
(2) d PdT = HvRT2
Solution
For Liquid Vapour, the equilibrium constant is Kp = P (vapour pressure).
van't Hoff equation: d KpdT = H RT2
⇒ d PdT = HvRT2 (Clausius–Clapeyron equation)
∵ Hv > 0 ⇒ vapour pressure increases with temperature.
Answer: (2)